U.S. patent application number 13/610003 was filed with the patent office on 2013-01-03 for semiconductor integrated circuit.
This patent application is currently assigned to RENESAS ELECTRONICS CORPORATION. Invention is credited to Takashi KAWAMOTO.
Application Number | 20130002360 13/610003 |
Document ID | / |
Family ID | 42222238 |
Filed Date | 2013-01-03 |
United States Patent
Application |
20130002360 |
Kind Code |
A1 |
KAWAMOTO; Takashi |
January 3, 2013 |
SEMICONDUCTOR INTEGRATED CIRCUIT
Abstract
A phase locked loop (PLL) which has a desired frequency
characteristic even though a manufacturing process of a
semiconductor integrated circuit has fluctuations. The
semiconductor integrated circuit includes the PLL and a control
unit. The PLL has a phase frequency detector, a loop filter, a
voltage controlled oscillator (VCO) and a divider. The VCO
comprises a voltage-current converter (VIC) and a ring oscillator.
In response to a control voltage, the VIC generates a control
current for setting each operating current of the ring oscillator.
The control unit switches the PLL to a calibration operating period
of its open loop and a normal operating period of its closed
loop.
Inventors: |
KAWAMOTO; Takashi; (Kodaira,
JP) |
Assignee: |
RENESAS ELECTRONICS
CORPORATION
Kawasaki-shi
JP
|
Family ID: |
42222238 |
Appl. No.: |
13/610003 |
Filed: |
September 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13351745 |
Jan 17, 2012 |
8289057 |
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13610003 |
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12622604 |
Nov 20, 2009 |
8134392 |
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13351745 |
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Current U.S.
Class: |
331/34 |
Current CPC
Class: |
H03L 7/10 20130101; H03L
7/0893 20130101; H03L 7/0995 20130101; H03L 7/18 20130101 |
Class at
Publication: |
331/34 |
International
Class: |
H03L 7/08 20060101
H03L007/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2008 |
JP |
2008-303616 |
Claims
1. A semiconductor integrated circuit comprising: a phase locked
loop; and a control unit, wherein the phase locked loop comprises a
phase frequency detector, a loop filter, a voltage controlled
oscillator and a divider, wherein a reference signal and a feedback
signal from an output of the divider are respectively capable of
being supplied to one input terminal of the phase frequency
detector and another input terminal thereof, wherein an output of
the phase frequency detector is supplied to a control input of the
voltage controlled oscillator via the loop filter, an oscillation
output signal of an output of the voltage controlled oscillator is
supplied to an input of the divider, and a frequency of the
oscillation output signal of the voltage controlled oscillator is
capable of being controlled in response to a control voltage
supplied to the control input, wherein the voltage controlled
oscillator comprises a voltage-current converter and a ring
oscillator, wherein the ring oscillator comprises delays of
odd-numbered stages, wherein the voltage-current converter
generates a control current in response to the control voltage to
thereby set each of operating currents of the delays of the ring
oscillator by the control current, wherein the voltage-current
converter comprises a frequency control sensitivity trimming
transistor for generating drain current in response to the control
voltage and a offset frequency trimming transistor for generating
drain offset current in response to a reference current, wherein
the control current is a current corresponding to the sum of the
drain current and the drain offset current, wherein gain of the
frequency control sensitivity trimming transistor and the drain
current can be adjusted by a first operation parameter of the
voltage-current converter of the voltage controlled oscillator,
wherein gain of the offset frequency trimming transistor and the
drain offset current can be adjusted by a second operation
parameter of the voltage-current converter of the voltage
controlled oscillator. wherein the control unit is capable of
switching the phase locked loop to a calibration operating period
and a normal operating period, wherein the control unit sets a
value of the first operation parameter of the voltage-current
converter of the voltage controlled oscillator and a value of the
second operation parameter of the voltage-current converter of the
voltage controlled oscillator, wherein during the normal operating
period, the phase locked loop is controlled to a closed loop by the
control unit, whereas during the calibration operating period, the
phase locked loop is controlled to an open loop by the control
unit, wherein during the normal operating period, the output of the
phase frequency detector is supplied via the loop filter to the
control input of the voltage controlled oscillator as the control
voltage of a predetermined level at the phase locked loop
controlled to the closed loop to thereby bring the frequency of the
oscillation output signal of the voltage controlled oscillator to a
predetermined frequency determined by the frequency of the
reference signal and a division ratio of the divider, wherein
during the calibration operating period, the measurement of the
frequency of the oscillation output signal of the voltage
controlled oscillator in a state in which a reference voltage
approximately equal in level to the control voltage of the
predetermined level is being supplied to the control input of the
voltage controlled oscillator at the phase locked loop controlled
to the open loop, is executed by the control unit, and wherein the
control unit sets a value of the first operation parameter of the
voltage-current converter of the voltage controlled oscillator in
such a manner that the frequency of the oscillation output signal
of the voltage controlled oscillator in the state in which the
reference voltage is being supplied to the voltage controlled
oscillator becomes approximately equal to the predetermined
frequency during the execution of the measurement of the
frequency.
2. The semiconductor integrated circuit according to claim 1,
wherein the phase locked loop further comprises a selector
controlled by the control unit, and wherein the selector selects
the control voltage of the predetermined level during the normal
operating period, and the selector selects the reference voltage
during the calibration operating period and supplies the selected
voltage to the control input of the voltage controlled
oscillator.
3. The semiconductor integrated circuit according to claim 2,
wherein prior to the setting of the value of the first operation
parameter of the voltage-current converter, the measurement of the
frequency of the oscillation output signal of the voltage
controlled oscillator in a state in which the control voltage
having a level of a ground potential is being supplied to the
control input of the voltage controlled oscillator of the phase
locked loop controlled to the open loop is executed by the control
unit during the calibration operating period, and wherein during
the calibration operating period, the control unit sets a value of
the second operation parameter of the voltage-current converter of
the voltage controlled oscillator, prior to the setting of the
value of the first operation parameter of the voltage-current
converter in such a manner that the frequency of the oscillation
output signal in the state in which the control voltage having the
level of the ground potential is being supplied to the voltage
controlled oscillator becomes approximately equal to a
predetermined offset frequency during the execution of the
measurement.
4. The semiconductor integrated circuit according to claim 3,
wherein during the calibration operating period, the selector
supplies the control voltage having the level of the ground
potential to the control input of the voltage controlled oscillator
of the phase locked loop controlled to the open loop, prior to the
setting of the value of the first operation parameter of the
voltage-current converter.
5. The semiconductor integrated circuit according to claim 4,
wherein after the value of the second operation parameter of the
voltage-current converter of the voltage controlled oscillator has
been set during the calibration operating period, another
measurement of the frequency of the oscillation output signal of
the voltage controlled oscillator in a state in which another
reference voltage higher than the level of the ground potential and
lower in level than the control voltage of the predetermined level
is being supplied to the control input of the voltage controlled
oscillator of the phase locked loop controlled to the open loop is
further executed by the control unit, and wherein during the
calibration operating period, the control unit sets the value of
the first operation parameter of the voltage-current converter of
the voltage controlled oscillator in such a manner that the
frequency of the oscillation output signal in the state in which
the other reference voltage is being supplied to the voltage
controlled oscillator becomes approximately equal to another
predetermined frequency lower than the predetermined frequency.
6. The semiconductor integrated circuit according to claim 5,
wherein after the value of the second operation parameter has been
set during the calibration operating period, the selector supplies
the other reference voltage to the control input of the voltage
controlled oscillator of the phase locked loop controlled to the
open loop.
7. The semiconductor integrated circuit according to claim 6,
wherein the phase locked loop further comprises a charge pump which
performs charge/discharge of the loop filter in response to the
output of the phase frequency detector.
8. The semiconductor integrated circuit according to claim 7,
wherein the charge pump comprises a first charge pump and a second
charge pump, wherein the first charge pump and the second charge
pump are driven in antiphase to each other in response to an up
output signal and a down output signal each used as the output of
the phase frequency detector to set a first charge/discharge
current of the first charge pump and a second charge/discharge
current of the second charge pump to a predetermined ratio, wherein
the loop filter comprises a resistor and a capacitor for
determining a zero point frequency, and one end of the resistor is
coupled to an input terminal of the loop filter and another end
thereof is coupled to a ground potential via the capacitor, wherein
the one and other ends of the resistor of the loop filter are
respectively driven by the first charge/discharge current of the
first charge pump and the second charge/discharge current of the
second charge pump, and wherein the resistor and the capacitor of
the loop filter are built in a semiconductor chip.
9. The semiconductor integrated circuit according to claim 8, which
is capable of being coupled between a pickup for performing data
reading and writing of a disk used as a storage media of a disk
recording/reproducing device, and a host computer, the
semiconductor integrated circuit comprising: a host interface that
supplies read data to the host computer and is supplied with write
data from the host computer; and a signal processing unit that
performs processing of a signal read from the pickup and performs
processing of a signal written into the pickup, wherein the phase
locked loop generates a clock signal used in at least one of the
host interface and the signal processing unit.
10. The semiconductor integrated circuit according to claim 9,
wherein the host interface is an ATA interface.
Description
CLAIM OF PRIORITY
[0001] The present application is a continuation of U.S. patent
application Ser. No. 13/351,745, filed Jan. 17, 2012, which is a
divisional of U.S. patent application Ser. No. 12/622,604, filed
Nov. 20, 2009, now U.S. Pat. No. 8,134,392, which claims priority
from Japanese patent application JP 2008-303616 filed on Nov. 28,
2008, the content of which is hereby incorporated by reference into
this application.
FIELD OF THE INVENTION
[0002] The present invention relates to a semiconductor integrated
circuit having a PLL built therein, and particularly to a
technology useful to provide a PLL able to have a desired frequency
characteristic even though a manufacturing process of a
semiconductor integrated circuit has some fluctuations.
BACKGROUND OF THE INVENTION
[0003] As has been well known, a phase locked loop (PLL) comprises
a voltage controlled oscillator (VCO), a phase detector, a loop
filter and a divider. An output of the phase detector is supplied
to an oscillation control input terminal of the voltage controlled
oscillator (VCO) via the loop filter, and a stable reference signal
is supplied to one input terminal of the phase detector. On the
other hand, an output signal of the voltage controlled oscillator
(VCO) is fed back to the other input terminal of the phase detector
via the divider. It is thus possible to stabilize the output
frequency of the voltage controlled oscillator (VCO) with respect
to a change in temperature, a variation with time, a variation in
power source, etc. The output signal of the VCO can hence be used
as a stable clock signal or the like for a semiconductor integrated
circuit.
[0004] For example, a PLL built in a semiconductor integrated
circuit mounted in a disk recording/reproducing device, which
accesses recording media such as hard disk (HDD), a compact disk
(CD), a digital video disk (DVD), a blue-ray disk (BD), etc.,
generates a clock signal for determining an access speed of the
recording medium and generates a clock signal for determining a
data transfer rate at an interface between a host device such as a
personal computer and the semiconductor integrated circuit.
[0005] There is thus a need for a calibration function for
adjusting the characteristic of the PLL at the time of shipment of
the semiconductor integrated circuit or at a calibration operating
period or the like just before a normal operation in such a manner
that the PLL built in the semiconductor integrated circuit
satisfies a desired characteristic.
[0006] Particularly in a semiconductor integrated circuit such as
an analog-digital mixed-signal processing LSI (hereinafter called
"ana-digi mixed LSI") or the like, a voltage controlled oscillator
(VCO) corresponding to an analog circuit needs to keep frequency
control sensitivity relatively low for the purpose of generating an
output signal of a high frequency and reducing frequency
jitter.
[0007] Further, the general-purpose ana-digi mixed LSI needs to
suppress fluctuations in manufacturing process for the purpose of
manufacturing it on a mass production line. For example, the
ana-digi mixed LSI is equipped with a PLL for the purpose of
generating an operation clock for a logic circuit and generating a
transmit signal clock. An analog circuit such as a voltage
controlled oscillator (VCO) or the like included in this PLL
greatly varies in characteristic due to fluctuations in
manufacturing process. Particularly, when an operating environment
large in temperature change is estimated or considered as in a case
where a manufacturing process such as a miniaturizing process or
the like fluctuates greatly, a case where the analog circuit is
used as an automobile mounting part, etc., there is a case where
the voltage controlled oscillator (VCO) or the like included in the
PLL cannot satisfy a desired characteristic. Thus, various
proposals for bringing the voltage controlled oscillator (VCO) of
the PLL to the desired characteristic have heretofore been carried
out.
[0008] First, a patent document 1 describes that a control voltage
for controlling an oscillation frequency of a voltage controlled
oscillator (VCO) is supplied to its corresponding gate of a
conversion MOS transistor of a voltage-current converter in an
operation current control unit, which converts the control voltage
to an operating current of a ring oscillator, and a drain current
of the conversion MOS transistor is supplied to an input terminal
of a current mirror to thereby determine the operating current of
the ring oscillator according to the current at an output terminal
of the current mirror. A conversion resistor between the source of
the conversion MOS transistor and a ground potential can be
selected to a low resistance and a high resistance. When the low
resistance is selected for the conversion resistor, the operating
current of the ring oscillator assumes a large value in response to
a predetermined control voltage, so that an oscillation signal of a
high frequency can be generated. When the high resistance is
selected as for the conversion resistor on the contrary, the
operating current of the ring oscillator assumes a small value in
response to the predetermined control voltage, so that an
oscillation signal of a low frequency can be generated. Further,
the patent document 1 also has described that such another resistor
that even though the control voltage is zero volt, the operating
current of the ring oscillator becomes a micro or minimal value and
the ring oscillator oscillates at an extremely low frequency, is
coupled between the input terminal of the current mirror of the
voltage-current converter and the ground potential.
[0009] Even in the case of a patent document 2, a control voltage
is supplied to its corresponding gate of a conversion MOS
transistor of a voltage-current converter, and a drain current of
the conversion MOS transistor is supplied to an input terminal of a
current mirror, thereby determining an operating current of a ring
oscillator of a voltage controlled oscillator (VCO) according to a
current from an output terminal of the current mirror. Further, the
patent document 2 describes the solution of a problem that due to a
low breakdown voltage of each MOS transistor by a miniaturized
manufacturing process, frequency control sensitivity of an
oscillation frequency vs control voltage at the conversion MOS
transistor of the voltage-current converter for generating the
operating current of the ring oscillator increases, so that a
jitter characteristic is degraded. In order to solve this problem,
the patent document 2 also describes that another current mirror
circuit such that even though the control voltage is zero volt, the
operating current of the ring oscillator becomes a minimal value
and the ring oscillator oscillates at an extremely low frequency,
is coupled between an input terminal of the current mirror of the
voltage-current converter and a ground potential.
[0010] Further, a patent document 3 also describes in a manner
similar to the patent document 2 that an offset current addition
circuit such that even though a control voltage is zero volt at a
voltage controlled oscillator (VCO), an operating current of a ring
oscillator becomes a minimal value and the ring oscillator
oscillates at an extremely low frequency, is coupled between an
input terminal of a current mirror of a voltage-current converter
and a ground potential. However, the voltage-current converter
described in the patent document 3 is used as a differential
voltage-current converter and larger in the number of elements than
the voltage-current converter described in the patent document 2.
[0011] [Patent Document 1] Japanese Unexamined Patent Publication
No. 2003-152507 [0012] [Patent Document 2] Japanese Unexamined
Patent Publication No. 2007-129501 [0013] [Patent Document 3]
Japanese Unexamined Patent Publication No. 2003-229764
SUMMARY OF THE INVENTION
[0014] Prior to the present invention, the present inventors et al.
have been involved in the study and development of a PLL built in a
semiconductor integrated circuit mounted to a disk
recording/reproducing device.
[0015] FIG. 26 is a diagram showing a voltage controlled oscillator
(VCO) included in the PLL examined by the present inventors et al.
prior to the present invention.
[0016] The voltage controlled oscillator (VCO) 5 shown in FIG. 26
comprises a voltage-current converter (VIC) 51 and a current
controlled oscillator (CCO) 52. The current controlled oscillator
(CCO) 52 configured as a ring oscillator comprises delays 521, 522
and 523 of odd-numbered stages.
[0017] An inverse output signal Fvcob and a non-inverse output
signal Fvco of the delay 523 of the final stage are respectively
supplied to a non-inverse input terminal and an inverse input
terminal of the delay 521 of the first stage. An inverse output
signal and a non-inverse output signal of the delay 521 are
respectively supplied to a non-inverse input terminal and an
inverse input terminal of the delay 522 of the next stage. An
inverse output signal and a non-inverse output signal of the delay
522 are respectively supplied to a non-inverse input terminal and
an inverse input terminal of the delay 523.
[0018] When a control voltage (Vc) for controlling an oscillation
frequency of the voltage controlled oscillator (VCO) 5 is supplied
to its corresponding input terminal of the voltage-current
converter (VIC) 51, the voltage-current converter (VIC) 51 executes
voltage-current conversion to generate a converted current
thereinside. This converted current is converted to an output
voltage (Vp) by the voltage-current converter (VIC) 51. The output
voltage (Vp) generated from an output terminal of the
voltage-current converter (VIC) 51 is supplied to the delays 521,
522 and 523 of the current controlled oscillator (CCO) 52 as a bias
voltage so that respective operating currents and delay times of
the delays 521, 522 and 523 are set. The oscillation frequency of
the voltage controlled oscillator (VCO) 5 is therefore decided.
[0019] FIG. 20 is a diagram showing a configuration of each of the
delays 521, 522 and 523 of the current controlled oscillator (CCO)
52 in the voltage controlled oscillator (VCO) 5 shown in FIG.
26.
[0020] The delay 521 (522, 523) shown in FIG. 20 has a first input
terminal i1 and a second input terminal i2 that respectively
function as a non-inverse input terminal and an inverse input
terminal and has a first output terminal o1 and a second output
terminal o2 that respectively function as an inverse output
terminal and a non-inverse output terminal.
[0021] A gate of a P channel MOS transistor 5212 and a gate of an N
channel MOS transistor 5216 are coupled to the first input terminal
i1. A drain of the P channel MOS transistor 5212, a drain of the N
channel MOS transistor 5216, a drain of a P channel MOS transistor
5213 and a gate of a P channel MOS transistor 5214 are coupled to
the first output terminal o1.
[0022] A gate of a P channel MOS transistor 5215 and a gate of an N
channel MOS transistor 5217 are coupled to the second input
terminal i2. A drain of the P channel MOS transistor 5215, a drain
of the N channel MOS transistor 5217, a drain of the P channel MOS
transistor 5214 and a gate of the P channel MOS transistor 5213 are
coupled to the second output terminal o2.
[0023] Sources of the two N channel MOS transistors 5216 and 5217
are coupled to a ground potential GND. Sources of the four P
channel MOS transistors 5212, 5213, 5214 and 5215 are coupled to a
source voltage V.sub.DD via a drain-source path of a bias P channel
MOS transistors 5211. An output voltage (Vp) generated from an
output terminal of the voltage-current converter (VIC) 51 of the
voltage controlled oscillator (VCO) 5 shown in FIG. 26 is supplied
to a gate of the bias P channel MOS transistor 5211. Thus, since
the operating currents and delay times of the delays 521, 522 and
523 that configure the current controlled oscillator (CCO) 52 of
the voltage controlled oscillator (VCO) 5 shown in FIG. 26 are set,
the oscillation frequency of the voltage controlled oscillator
(VCO) 5 is determined.
[0024] FIG. 27 is a diagram showing a configuration of the
voltage-current converter (VIC) 51 of the voltage controlled
oscillator (VCO) 5 shown in FIG. 26.
[0025] The voltage-current converter (VIC) 51 shown in FIG. 27
comprises an N channel MOS transistor 511 that functions as a
voltage-current conversion element and a P channel MOD transistor
512 that functions as a current-voltage conversion element. A
converted current (Ip) is generated from a drain of the N channel
MOS transistor 511 in response to the control voltage (Vc) supplied
to its corresponding gate of the N channel MOS transistor 511 whose
source is coupled to the ground potential GND. The generated
converted current is supplied to the P channel MOS transistor 512.
Since a gate and a drain of the P channel MOS transistor 512 whose
source is coupled to the source voltage V.sub.DD are coupled to
each other, the P channel MOS transistor 512 operates as a diode.
Thus, the converted current (Ip) from the drain of the N channel
MOS transistor 511 is converted to an output voltage (Vp) by the P
channel MOS transistor 512 used as the diode.
[0026] The output voltage (Vp) generated at both ends of the P
channel MOS transistor 512 of the voltage-current converter (VIC)
51 shown in FIG. 27 is supplied between the source and gate of the
bias P channel MOS transistor 5211 lying inside the delay 521 (522,
523) shown in FIG. 20. Thus, since the operating currents and delay
times of the delays 521, 522 and 523 that configure the current
controlled oscillator (CCO) 52 of the voltage controlled oscillator
(VCO) 5 shown in FIG. 26 are set, the oscillation frequency of the
voltage controlled oscillator (VCO) 5 is determined.
[0027] FIG. 28 is a diagram showing the characteristics of
frequency control sensitivity of oscillation frequency vs control
voltages of the voltage controlled oscillator (VCO) 5 shown in FIG.
26, which has been examined by the present inventors et al. prior
to the present invention. The vertical axis of FIG. 28 indicates
the frequency of an oscillation output signal Fvco, and the
horizontal axis of FIG. 28 indicates the level of a control voltage
Vc supplied to the voltage-current converter (VIC) 51.
[0028] FIG. 28 shows a characteristic where the voltage controlled
oscillator (VCO) 5 shown in FIG. 26 is manufactured in a
non-miniaturized CMOS manufacturing process at which the minimum
line width is 0.18 .mu.m, and a characteristic where the voltage
controlled oscillator (VCO) 5 shown in FIG. 26 is manufactured in a
miniaturized CMOS manufacturing process at which the minimum line
width is 45 nm.
[0029] Assume that in the 0.18 .mu.m non-miniaturized CMOS
manufacturing process, for example, the source voltage V.sub.DD is
1.8V and the threshold voltage of the N channel MOS transistor 511
corresponding to the voltage-current conversion element of the
voltage-current converter (VIC) 51 shown in FIG. 27 is a relatively
large value Vth180. When an output frequency (Fo) of the PLL and a
control voltage Vc placed in a locked state of the PLL are set
after doing so, frequency control sensitivity Kv180 of an
oscillation frequency vs control voltage is determined. Assuming
that in the example shown in FIG. 28, the control voltage Vc in the
locked state is 1.3V, for example, the frequency control
sensitivity (Kv180) becomes a relatively small value of
Kv=Fo/(1.3V-Vth180).
[0030] On the other hand, in the miniaturized CMOS manufacturing
process at which the minimum line width is 45 nm, the source
voltage V.sub.DD is assumed to be 1.0V for example and the
threshold voltage of the N channel MOS transistor 511 corresponding
to the voltage-current conversion element of the voltage-current
converter (VIC) 51 shown in FIG. 27 is assumed to be a relatively
small value Vth45. Assuming that the voltage corresponding to the
control voltage Vc placed in the locked state of the PLL is 0.7V,
for example, the frequency control sensitivity (Kv45) becomes a
relatively large value of Kv=Fo/(0.7-Vth45).
[0031] Thus, there is a tendency that the frequency control
sensitivity Kv increases due to the low threshold voltage and the
low source voltage according to the miniaturized CMOS manufacturing
process. A problem, however, arises in that since the oscillation
output frequency of the voltage controlled oscillator (VCO)
fluctuates greatly due to noise contained in the control voltage Vc
where the value of the frequency control sensitivity Kv is
extremely high, a satisfactory jitter characteristic is not
obtained.
[0032] When the frequency control sensitivity Kv increases due to
the miniaturized CMOS manufacturing process, the frequency band of
the PLL is brought to band widening correspondingly. Although there
is, however, a need to limit the frequency band of the PLL to a
certain degree of range in order to meet noise spectra and other
characteristics defined by various standards or the like of
electronic equipment, there is a tendency that it becomes difficult
to comply with the various standards due to the band widening of
the PLL based on the miniaturized CMOS manufacturing process.
[0033] Further, there has also been revealed a problem that
fluctuations in the frequency characteristic of the PLL such as the
frequency control sensitivity Kv or the like also become large due
to the fact that relative fluctuations in the threshold voltage
become large with a decrease in the threshold voltage of a
miniaturize MOS transistor of a semiconductor integrated
circuit.
[0034] On the other hand, in the PLL, the output of a phase
frequency detector is supplied to its corresponding input of a
charge pump, and a loop filter for generating the control voltage
Vc for controlling the oscillation frequency of the voltage
controlled oscillator (VCO) is driven by charging/discharging of
the output of the charge pump. It has, however, also been revealed
by examinations of the present inventors et al. that the
characteristic of the charge pump is also affected by the
miniaturized CMOS manufacturing process.
[0035] FIG. 29 is a diagram showing a configuration of a charge
pump examined by the present inventors et al. prior to the present
invention.
[0036] The charge pump 2 shown in FIG. 29 comprises a current
source 25 for generating a charging current, a P channel MOS
transistor 26 driven by an up output UP of a phase frequency
detector, an N channel MOS transistor 27 driven by a down output DN
of the phase frequency detector, and a current source 28 for
generating a discharging current.
[0037] Constant currents of the charging current source 25 and the
discharging current source 28 are assumed to be Icp. The on
resistance and threshold voltage of a P channel MOS transistor of
the charging current source 25 are respectively assumed to be Ronp
and Vthp. The on resistance and threshold voltage of an N channel
MOS transistor of the discharging current source 28 are
respectively assumed to be Ronn and Vthn.
[0038] A control voltage Vc of the loop filter for controlling the
oscillation frequency of the voltage controlled oscillator (VCO) is
generated from an output terminal to which the drain of the P
channel MOS transistor 26 of the charge pump 2 and the drain of the
N channel MOS transistor 27 thereof are coupled. An operation range
in which the charging current source 25 and the discharging current
source 28 of the charge pump 2 cause a predetermined constant
current Icp to flow therethrough, is limited as follows.
[0039] FIG. 30 is a diagram showing the relationship between the
current Icp flowing through the charging current source 25 and the
discharging current source 28 at the charge pump 2 shown in FIG. 29
and the control voltage Vc at the output terminal of the charge
pump 2.
[0040] The value of the control voltage Vc corresponds to
approximately half the source voltage V.sub.DD approximately in the
central part of FIG. 30. The P channel MOS transistor of the
charging current source 25 and the N channel MOS transistor of the
discharging current source 28 respectively operate in a saturated
region. Thus, the P channel MOS transistor of the charging current
source 25 and the N channel MOS transistor of the discharging
current source 28 allow predetermined constant currents Icp to flow
therethrough respectively approximately in the central part of FIG.
30.
[0041] When, however, the control voltage Vc of the output terminal
of the charge pump 2 is reduced and becomes lower than a level of
Vthn+Icp*Ronn, the N channel MOS transistor of the discharging
current source 28 operates in a linear region. Thus, since the
drain current of the N channel MOS transistor of the discharging
current source 28 is reduced in proportion to a low drain-source
voltage, the charging current of the N channel MOS transistor of
the discharging current source 28 becomes a value smaller than the
predetermined constant current Icp.
[0042] On the other hand, when the control voltage Vc of the output
terminal of the charge pump 2 rises and the control voltage Vc
becomes higher than a level of V.sub.DD-Vthp-Icp*Ronp, the P
channel MOS transistor of the charging current source 25 operates
in a linear region. Thus, since the drain current of the P channel
MOS transistor of the charging current source 25 is reduced in
proportion to a low source-drain voltage, the discharging current
of the P channel MOS transistor of the charging current source 25
becomes a value smaller than the predetermined constant current
Icp.
[0043] Thus, as compared with the frequency control sensitivity of
the voltage controlled oscillator (VCO) where the control voltage
Vc of the output terminal of the charge pump 2 changes at each of
the right and left parts of FIG. 30, the value of the frequency
control sensitivity of the voltage controlled oscillator (VCO)
where the control voltage Vc changes approximately in the central
part of FIG. 30 becomes high.
[0044] Accordingly, it has been revealed by examinations of the
present inventors et al. that it is necessary to consider the
jitter characteristic of the voltage controlled oscillator (VCO) in
the PLL in consideration of an increase in the frequency control
sensitivity Kv due to the miniaturized CMOS manufacturing process
shown in FIG. 28 and an increase in the frequency control
sensitivity Kv in a region in which the control voltage Vc
corresponding to the output of the charge pump 2, which has been
shown approximately in the central part of FIG. 30, is relatively
high.
[0045] The present invention has been made as a result of the above
examinations of the present inventors et al. prior to the present
invention.
[0046] Accordingly, an object of the present invention is to
provide a PLL able to have a desired frequency characteristic even
though a manufacturing process of a semiconductor integrated
circuit has some fluctuations.
[0047] Further, another object of the present invention is to set
frequency control sensitivity of a voltage controlled oscillator of
a PLL to a desired characteristic.
[0048] A further object of the present invention is to improve a
jitter characteristic of a voltage controlled oscillator of a
PLL.
[0049] The above, other objects and novel features of the present
invention will become apparent from the description of the present
specification and the accompanying drawings.
[0050] A typical one of the inventions disclosed in the present
application will be explained in brief as follows:
[0051] A typical semiconductor integrated circuit of the present
invention comprises a phase locked loop (PLL) and a control unit
(9).
[0052] The phase locked loop comprises a phase frequency detector
(1), a loop filter (3), a voltage controlled oscillator (8) and a
divider (6).
[0053] The voltage controlled oscillator (8) comprises a
voltage-current converter (81) and a ring oscillator (52) (refer to
FIG. 2).
[0054] The ring oscillator (52) has delays (521, 522 and 523) of
odd-numbered stages (refer to FIG. 2).
[0055] The voltage-current converter (81) generates a control
current (Ip) in response to the control voltage (Vc) (refer to FIG.
3) and causes the control current (Ip) to set respective operating
currents of the delays of the ring oscillator (52) (refer to FIG.
2).
[0056] The control unit (9) switches the phase locked loop (PLL) to
a calibration operating period and a normal operating period.
[0057] During the normal operating period, the phase locked loop
(PLL) is controlled to a closed loop by the control unit (9),
whereas during the calibration operating period, the phase locked
loop (PLL) is controlled to an open loop by the control unit
(9).
[0058] During the normal operating period, the frequency of the
oscillation output signal of the voltage controlled oscillator is
brought to a predetermined frequency (B) determined by the
frequency of the reference signal (Fref) and a division ratio of
the divider (6). During the calibration operating period, the
measurement of the frequency of the oscillation output signal
(Fvco) of the voltage controlled oscillator (8) in a state in which
a reference voltage (V.sub.REF) of a level approximately equal to
the control voltage (Vc) of the predetermined level is being
supplied to its corresponding control input of the voltage
controlled oscillator (8), is executed by the control unit (9)
(refer to FIGS. 5 and 7).
[0059] The control unit (9) sets the value of a first operation
parameter (T) of the voltage-current converter (81) of the voltage
controlled oscillator (8) in such a manner that the frequency of
the oscillation output signal of the voltage controlled oscillator
in the state in which the reference voltage has been supplied to
the voltage controlled oscillator becomes approximately equal to
the predetermined frequency (B) during the execution of the
measurement of the frequency (refer to Steps 56 through 59 of FIG.
5).
[0060] An advantageous effect obtained by a typical one of the
inventions disclosed in the present application will be explained
in brief as follows:
[0061] There can be provided a PLL able to have a desired frequency
characteristic even though a manufacturing process of a
semiconductor integrated circuit has some fluctuations.
BRIEF DESCRIPTION OF THE DRAWINGS
[0062] FIG. 1 is a diagram for describing an overall configuration
of a PLL built in a semiconductor integrated circuit according to a
first embodiment of the present invention;
[0063] FIG. 2 is a diagram showing a configuration of a voltage
controlled oscillator included in the PLL according to the first
embodiment of the present invention shown in FIG. 1;
[0064] FIG. 3 is a diagram illustrating a configuration of a
voltage-current converter included in the voltage controlled
oscillator shown in FIG. 2;
[0065] FIG. 4 is a diagram depicting a configuration of a frequency
control sensitivity trimming N channel MOS transistor included in
the voltage-current converter shown in FIG. 3;
[0066] FIG. 5 is a diagram for describing a calibration operation
of the PLL according to the first embodiment of the present
invention shown in FIG. 1;
[0067] FIG. 6 is a diagram showing the manner in which the offset
frequency of a signal outputted from the voltage controlled
oscillator increases in response to the updating of an offset
frequency adjustment signal in the calibration operation of the PLL
according to the first embodiment of the present invention shown in
FIG. 1;
[0068] FIG. 7 is a diagram illustrating the manner in which the
frequency of a signal outputted from the voltage controlled
oscillator increases in response to the updating of a frequency
control sensitivity adjustment signal in the calibration operation
of the PLL according to the first embodiment of the present
invention shown in FIG. 1;
[0069] FIG. 8 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a second
embodiment of the present invention;
[0070] FIG. 9 is a diagram for describing a calibration operation
of the PLL according to the second embodiment of the present
invention shown in FIG. 8;
[0071] FIG. 10 is a diagram showing the manner in which the offset
frequency of a signal outputted from a voltage controlled
oscillator increases in response to the updating of an offset
frequency adjustment signal in the calibration operation of the PLL
according to the second embodiment of the present invention shown
in FIG. 8;
[0072] FIG. 11 is a diagram illustrating the manner in which the
frequency of a signal outputted from the voltage controlled
oscillator increases in response to the updating of a frequency
control sensitivity adjustment signal in the calibration operation
of the PLL according to the second embodiment of the present
invention shown in FIGS. 8 and 9;
[0073] FIG. 12 is a diagram depicting a configuration of a PLL
built in a semiconductor integrated circuit according to a third
embodiment of the present invention;
[0074] FIG. 13 is a diagram showing a configuration of a voltage
controlled oscillator included in the PLL according to the third
embodiment of the present invention shown in FIG. 12;
[0075] FIG. 14 is a diagram illustrating a configuration of a
voltage-current converter included in the voltage controlled
oscillator shown in FIG. 13;
[0076] FIG. 15 is a diagram for describing a calibration operation
of the PLL according to the third embodiment of the present
invention shown in FIGS. 12 through 14;
[0077] FIG. 16 is a diagram showing the manner in which the
oscillation frequency of a signal outputted from the voltage
controlled oscillator increases in response to the updating of an
adjustment signal T and an adjustment signal L and the updating of
an adjustment signal T and an adjustment signal L in the
calibration operation of the PLL according to the third embodiment
of the present invention shown in FIGS. 12 through 15;
[0078] FIG. 17 is a diagram illustrating the manner in which the
frequency of a signal outputted from the voltage controlled
oscillator increases in response to the updating of an adjustment
signal G in the calibration operation of the PLL according to the
third embodiment of the present invention shown in FIGS. 12 through
16;
[0079] FIG. 18 is a diagram showing another configuration of the
voltage-current converter included in the voltage controlled
oscillator shown in FIG. 13;
[0080] FIG. 19 is a diagram illustrating a configuration of a
selector included in the frequency control sensitivity trimming N
channel MOS transistor shown in FIG. 4;
[0081] FIG. 20 is a diagram depicting a configuration of each of
delay circuits of current controlled oscillators of the voltage
controlled oscillators shown in FIGS. 2 and 26;
[0082] FIG. 21 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a fourth
embodiment of the present invention;
[0083] FIG. 22 is a diagram illustrating a configuration of a PLL
built in a semiconductor integrated circuit according to a fifth
embodiment of the present invention;
[0084] FIG. 23 is a diagram depicting a configuration of a PLL
built in a semiconductor integrated circuit according to a sixth
embodiment of the present invention;
[0085] FIG. 24 is a diagram showing a configuration of an optical
disk apparatus equipped with a semiconductor integrated circuit
according to an eighth embodiment of the present invention;
[0086] FIG. 25 is a diagram illustrating a configuration of an
optical disk apparatus equipped with a semiconductor integrated
circuit according to a ninth embodiment of the present
invention;
[0087] FIG. 26 is a diagram showing a voltage controlled oscillator
included in a PLL examined by the present inventors et al. prior to
the present invention;
[0088] FIG. 27 is a diagram illustrating a configuration of a
voltage-current converter of the voltage controlled oscillator
shown in FIG. 26;
[0089] FIG. 28 is a diagram showing the characteristics of
frequency control sensitivity of oscillation frequency vs control
voltages of the voltage controlled oscillator shown in FIG. 26,
which has been examined by the present inventors et al. prior to
the present invention;
[0090] FIG. 29 is a diagram depicting a configuration of a charge
pump examined by the present inventors et al. prior to the present
invention;
[0091] FIG. 30 is a diagram showing the relationship between
currents flowing through a charging current source and a
discharging current source at the charge pump shown in FIG. 29 and
a control voltage at an output terminal of the charge pump;
[0092] FIG. 31 is a diagram illustrating a configuration of a PLL
built in a semiconductor integrated circuit according to a seventh
embodiment of the present invention;
[0093] FIG. 32 is a diagram for describing an operation of the
voltage-current converter shown in FIG. 3;
[0094] FIG. 33 is a diagram for describing an operation of the
voltage-current converter shown in FIG. 3;
[0095] FIG. 34 is a diagram showing a frequency characteristic L1
of the voltage controlled oscillator examined prior to the present
invention by the present inventors et al., which includes the
voltage-current converter of FIG. 27 and has been shown in FIG. 26,
and a frequency characteristic L2 of the voltage controlled
oscillator according to the first embodiment of the present
invention, which has been described in FIGS. 1 through 7 and FIGS.
32 and 33; and
[0096] FIG. 35 is a diagram showing the dependence of a control
current Ip flowing through a P channel MOS transistor 81p5 on a
control voltage Vc at the voltage-current converter shown in FIG.
14.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Typical Embodiments
[0097] A summary of typical embodiments of the invention disclosed
in the present application will first be explained. Reference
numerals of the accompanying drawings referred to with parentheses
in the description of the summary of the typical embodiments only
illustrate elements included in the concept of components to which
the reference numerals are given.
[0098] [1] A semiconductor integrated circuit according to a
typical embodiment of the present invention comprises a phase
locked loop (PLL) and a control unit (9).
[0099] The phase locked loop comprises a phase frequency detector
(1), a loop filter (3), a voltage controlled oscillator (8) and a
divider (6).
[0100] A reference signal (Fref) and a feedback signal (Fb)
outputted from the divider (6) can respectively be supplied to one
input terminal of the phase frequency detector (1) and the other
input terminal thereof.
[0101] An output of the phase frequency detector (1) is supplied to
a control input of the voltage controlled oscillator (8) via the
loop filter (3). An oscillation output signal (Fvco) of the output
of the voltage controlled oscillator (8) is supplied to the input
of the divider (6). The frequency of the oscillation output signal
(Fvco) of the voltage controlled oscillator (8) can be controlled
in response to a control voltage (Vc) supplied to the control input
(refer to FIG. 1).
[0102] The voltage controlled oscillator (8) comprises a
voltage-current converter (81) and a ring oscillator (52) (refer to
FIG. 2).
[0103] The ring oscillator (52) has delays (521, 522 and 523) of
odd-numbered stages (refer to FIG. 2).
[0104] The voltage-current converter (81) generates a control
current (Ip) in response to the control voltage (Vc) (refer to FIG.
3) and causes the control current (Ip) to set respective operating
currents of the delays of the ring oscillator (52) (refer to FIG.
2).
[0105] The control unit (9) is capable of switching the phase
locked loop (PLL) to a calibration operating period and a normal
operating period.
[0106] During the normal operating period, the phase locked loop
(PLL) is controlled to a closed loop by the control unit (9),
whereas during the calibration operating period, the phase locked
loop (PLL) is controlled to an open loop by the control unit
(9).
[0107] During the normal operating period, the output of the phase
frequency detector (1) is supplied via the loop filter (3) to the
control input of the voltage controlled oscillator (8) as the
control voltage (Vc) having a predetermined level at the phase
locked loop (PLL) controlled to the closed loop, so that the
frequency of the oscillation output signal of the voltage
controlled oscillator is brought to a predetermined frequency (B)
decided by the frequency of the reference signal (Fref) and a
division ratio of the divider (6).
[0108] During the calibration operating period, the measurement of
the frequency of the oscillation output signal (Fvco) of the
voltage controlled oscillator (8) in a state in which a reference
voltage (V.sub.REF) of a level approximately equal to the control
voltage (Vc) of the predetermined level has been supplied to the
control input of the voltage controlled oscillator (8) at the phase
locked loop (PLL) controlled to the open loop, is executed by the
control unit (9) (refer to FIGS. 5 and 7).
[0109] The control unit (9) sets the value of a first operation
parameter (T) of the voltage-current converter (81) of the voltage
controlled oscillator (8) in such a manner that the frequency of
the oscillation output signal of the voltage controlled oscillator
in the state in which the reference voltage has been supplied to
the voltage controlled oscillator becomes approximately equal to
the predetermined frequency (B) during the execution of the
measurement of the frequency (refer to Steps 56 through 59 of FIG.
5).
[0110] According to the embodiment, a reference voltage of a level
approximately equal to a control voltage of a predetermined level
at which an oscillation output signal of a predetermined frequency
is generated from a voltage controlled oscillator during a normal
operating period of PLL, is supplied to the voltage controlled
oscillator during a calibration operating period. While the
measurement of the frequency of the oscillation output signal of
the voltage controlled oscillator during the calibration operating
period is being performed, a control unit sets the value of a first
operation parameter of a voltage-current converter of the voltage
controller oscillator in such a manner that the frequency of the
oscillation output signal of the voltage controlled oscillator
supplied with the reference voltage becomes approximately equal to
a predetermined frequency.
[0111] Thus, according to the embodiment, there can be provided a
PLL able to have a desired frequency characteristic even though the
manufacturing process of the semiconductor integrated circuit has
some variations.
[0112] In a semiconductor integrated circuit according to a
preferred embodiment, the phase locked loop (PLL) further comprises
a selector (7) controlled by the control unit (9).
[0113] The selector (7) selects the control voltage (Vc) of the
predetermined level during the normal operating period. On the
other hand, the selector (7) selects the reference voltage
(V.sub.REF) during the calibration operating period and supplies
the selected voltage to the control input of the voltage controlled
oscillator (8) (refer to FIG. 1).
[0114] In another preferred embodiment, during the calibration
operating period, the measurement of the frequency of the
oscillation output signal (Fvco) of the voltage controlled
oscillator (8) lying in the state in which the control voltage (Vc)
having a level of a ground potential (GND) is supplied to the
control input of the voltage controlled oscillator (8) of the phase
locked loop (PLL) controlled to the open loop, is executed by the
control unit (9) prior to the value of the first operation
parameter (T) of the voltage-current converter (81) being set
(refer to FIGS. 5 and 7).
[0115] During the calibration operating period, the control unit
(9) sets the value of a second operation parameter (0) of the
voltage-current converter (81) of the voltage controlled oscillator
(8) prior to the setting of the value of the first operation
parameter (T) of the voltage-current converter (81) in such a
manner that the frequency of the oscillation output signal in the
state in which the control voltage (Vc) having the level of the
ground potential (GND) has been supplied to the voltage controlled
oscillator becomes approximately equal to a predetermined offset
frequency (A) during the execution of the measurement (refer to
Steps 52 through 54 of FIG. 5).
[0116] In a further preferred embodiment, the selector (7) supplies
the control voltage (Vc) having the level of the ground potential
(GND) to the control input of the voltage controlled oscillator (8)
of the phase locked loop (PLL) controlled to the open loop, prior
to the setting of the value of the first operation parameter (T) of
the voltage-current converter (81) during the calibration operating
period (refer to FIG. 1).
[0117] In yet another preferred embodiment, after the value of the
second operation parameter (0) of the voltage-current converter
(81) of the voltage controlled oscillator (8) has been set during
the calibration operating period, another measurement (FIG. 9:
Steps 94 and 95) of the frequency of the oscillation output signal
(Fvco) of the voltage controlled oscillator (8) in the state in
which another reference voltage (V.sub.REF1) of a level higher than
the level of the ground potential (GND) and lower than the control
voltage (Vc) of the predetermined level has been supplied to the
control input of the voltage controlled oscillator (8) of the phase
locked loop (PLL) controlled to the open loop, is further executed
by the control unit (9) (refer to FIGS. 8, 9, 10 and 11).
[0118] During the calibration operating period, the control unit
(9) sets the value of the first operation parameter (T) of the
voltage-current converter (81) of the voltage controlled oscillator
(8) in such a manner that the frequency of the oscillation output
signal in the state in which the other reference voltage
(V.sub.REF1) referred to above has been supplied to the voltage
controlled oscillator, becomes approximately equal to another
predetermined frequency (B-C) lower than the predetermined
frequency (B) during the execution of another measurement (refer to
Steps 95 through 99 of FIG. 9).
[0119] In a still further preferred embodiment, after the value of
the second operation parameter (0) has been set during the
calibration operating period, the selector (7) supplies the other
reference voltage (V.sub.REF1) to the control input of the voltage
controlled oscillator (8) of the phase locked loop (PLL) controlled
to the open loop (refer to FIG. 8).
[0120] In a semiconductor integrated circuit according to a
specific embodiment, the phase locked loop (PLL) further comprises
a charge pump (2) which charges/discharges the loop filter (3) in
response to the output of the phase frequency detector (1) (refer
to FIG. 1).
[0121] In a more specific embodiment, the charge pump comprises a
first charge pump (2a) and a second charge pump (2b).
[0122] The first charge pump (2a) and the second charge pump (2b)
are driven in antiphase to each other in response to an up output
signal (UP) and a down output signal (DN) each used as the output
of the phase frequency detector (1) so that a first
charge/discharge current (i1) of the first charge pump (2a) and a
second charge/discharge current (i2) of the second charge pump (2b)
are respectively set to a predetermined ratio (.beta.).
[0123] The loop filter (3) comprises a resistor (R1) and a
capacitor (C1) for determining a zero point frequency (f1). One end
of the resistor (R1) is coupled to an input terminal of the loop
filter (3), and the other end thereof is coupled to a ground
potential (GND) via the capacitor (C1).
[0124] The one and other ends of the resistor (R1) of the loop
filter (3) are respectively driven by the first charge/discharge
current (i1) of the first charge pump (2a) and the second
charge/discharge current (i2) of the second charge pump (2b).
[0125] The resistor (R1) and the capacitor (C1) of the loop filter
(3) are built in a semiconductor chip (refer to FIG. 31).
[0126] A semiconductor integrated circuit according to a still more
specific embodiment can be coupled between a pickup for performing
data reading and writing of a disk used as a storage media of a
disk recording/reproducing device, and a host computer.
[0127] The semiconductor integrated circuit comprises a host
interface (2411, 2511) which supplies read data to the host
computer and is supplied with write data from the host
computer.
[0128] The semiconductor integrated circuit comprises a signal
processing unit (2412, 2512) which performs the processing of a
signal read from the pickup and performs the processing of a signal
written into the pickup (refer to FIGS. 24 and 25).
[0129] The phase locked loop (PLL) generates a clock signal used in
at least one of the host interface and the signal processing
unit.
[0130] In the most specific embodiment, the host interface (2411,
2511) is an ATA interface.
[0131] [2] A semiconductor integrated circuit according to a
typical embodiment of another aspect of the present invention
comprises a phase locked loop (PLL) and a control unit (9).
[0132] The phase locked loop comprises a phase frequency detector
(1), a loop filter (3), a voltage controlled oscillator (8) and a
divider (6).
[0133] A reference signal (Fref) and a feedback signal (Fb)
outputted from the divider (6) can respectively be supplied to one
input terminal of the phase frequency detector (1) and the other
input terminal thereof.
[0134] An output of the phase frequency detector (1) is supplied to
a control input of the voltage controlled oscillator (8) via the
loop filter (3). An oscillation output signal (Fvco) of an output
of the voltage controlled oscillator (8) is supplied to the input
of the divider (6). The frequency of the oscillation output signal
(Fvco) of the voltage controlled oscillator (8) can be controlled
in response to a control voltage (Vc) supplied to the control input
(refer to FIG. 12).
[0135] The voltage controlled oscillator (8) comprises a
voltage-current converter (81) and a ring oscillator (52) (refer to
FIG. 13).
[0136] The ring oscillator (52) has delays (521, 522 and 523) of
odd-numbered stages (refer to FIG. 13).
[0137] The voltage-current converter (81) generates a control
current (Ip) in response to the control voltage (Vc) (refer to FIG.
14) and causes the control current (Ip) to set respective operating
currents of the delays of the ring oscillator (52) (refer to FIG.
13).
[0138] The control unit (9) is capable of switching the phase
locked loop (PLL) to a calibration operating period and a normal
operating period.
[0139] During the normal operating period, the phase locked loop
(PLL) is controlled to a closed loop by the control unit (9),
whereas during the calibration operating period, the phase locked
loop (PLL) is controlled to an open loop by the control unit
(9).
[0140] During the normal operating period, the output of the phase
frequency detector (1) is supplied via the loop filter (3) to the
control input of the voltage controlled oscillator (8) as the
control voltage (Vc) having a predetermined level at the phase
locked loop (PLL) controlled to the closed loop, so that the
frequency of the oscillation output signal of the voltage
controlled oscillator is brought to a predetermined frequency (B)
decided by the frequency of the reference signal (Fref) and a
division ratio of the divider (6).
[0141] During the calibration operating period, a first measurement
of the frequency of the oscillation output signal (Fvco) of the
voltage controlled oscillator (8) in a state in which a first
reference voltage (V.sub.REF1) of a level higher than a ground
potential (GND) and low relatively is being supplied to the control
input of the voltage controlled oscillator (8), is executed by the
control unit (9) at the phase locked loop (PLL) controlled to the
open loop (refer to FIGS. 15 and 16).
[0142] The control unit (9) sets the value of a first operation
parameter (T, L) of the voltage-current converter (81) of the
voltage controlled oscillator (8) in such a manner that the
frequency of the oscillation output signal of the voltage
controlled oscillator in the state in which the first reference
voltage (V.sub.REF1) has been supplied to the voltage controlled
oscillator becomes approximately equal to the first predetermined
frequency (A) during the execution of the first measurement of the
frequency (refer to Steps 150 through 158 of FIG. 15).
[0143] During the calibration operating period, a second
measurement of the frequency of the oscillation output signal
(Fvco) of the voltage controlled oscillator (8) in a state in which
a second reference voltage (V.sub.REF2) of a level higher than the
first reference voltage (V.sub.REF1) and approximately equal to the
control voltage (Vc) of the predetermined level is being supplied
to the control input of the voltage controlled oscillator (8), is
executed by the control unit (9) after the setting of the value of
the first operation parameter (T, L) of the voltage-current
converter (81) (refer to FIGS. 15 and 17).
[0144] The control unit (9) sets the value of the second operation
parameter (G) of the voltage-current converter (81) of the voltage
controlled oscillator (8) in such a manner that the frequency of
the oscillation output signal of the voltage controlled oscillator
in the state in which the second reference voltage (V.sub.REF2) has
been supplied to the voltage controlled oscillator becomes
approximately equal to a second predetermined frequency (B) higher
than the first predetermined frequency (A) during the execution of
the second measurement of the frequency (refer to Steps 159 through
1513 of FIG. 15).
[0145] Thus, according to the embodiment, there can be provided a
PLL able to have a desired frequency characteristic even though the
manufacturing process of the semiconductor integrated circuit has
some fluctuations.
[0146] In a semiconductor integrated circuit according to a
preferred embodiment, the phase locked loop (PLL) further comprises
a selector (7) controlled by the control unit (9).
[0147] The selector (7) selects the control voltage (Vc) of the
predetermined level during the normal operating period. On the
other hand, the selector (7) selects one of the first reference
voltage (V.sub.REF1) and the second reference voltage (V.sub.REF2)
during the calibration operating period and supplies the selected
voltage to the control input of the voltage controlled oscillator
(8) (refer to FIG. 12).
[0148] In a semiconductor integrated circuit according to another
preferred embodiment, the phase locked loop (PLL) further comprises
a charge pump (2) which performs the discharge/discharge of the
loop filter (3) in response to the output of the phase frequency
detector (1) (refer to FIG. 12).
[0149] In a further preferred embodiment, the charge pump comprises
a first charge pump (2a) and a second charge pump (2b).
[0150] The first charge pump (2a) and the second charge pump (2b)
are driven in antiphase to each other in response to an up output
signal (UP) and a down output signal (DN) each used as the output
of the phase frequency detector (1) so that a first
charge/discharge current (i1) of the first charge pump (2a) and a
second charge/discharge current (i2) of the second charge pump (2b)
are respectively set to a predetermined ratio (.beta.).
[0151] The loop filter (3) comprises a resistor (R1) and a
capacitor (C1) for determining a zero point frequency (f1). One end
of the resistor (R1) is coupled to an input terminal of the loop
filter (3), and the other end thereof is coupled to a ground
potential (GND) via the capacitor (C1).
[0152] The one and other ends of the resistor (R1) of the loop
filter (3) are respectively driven by the first charge/discharge
current (i1) of the first charge pump (2a) and the second
charge/discharge current (i2) of the second charge pump (2b).
[0153] The resistor (R1) and the capacitor (C1) of the loop filter
(3) are built in a semiconductor chip (refer to FIG. 31).
[0154] A semiconductor integrated circuit according to a more
preferred embodiment can be coupled between a pickup for performing
data reading and writing of a disk used as a storage media of a
disk recording/reproducing device, and a host computer.
[0155] The semiconductor integrated circuit comprises a host
interface (2411, 2511) which supplies read data to the host
computer and is supplied with write data from the host
computer.
[0156] The semiconductor integrated circuit comprises a signal
processing unit (2412, 2512) which performs the processing of a
signal read from the pickup and performs the processing of a signal
written into the pickup (refer to FIGS. 24 and 25).
[0157] The phase locked loop (PLL) generates a clock signal used in
at least one of the host interface and the signal processing
unit.
[0158] In a still more specific embodiment, the host interface
(2411, 2511) is an ATA interface.
DESCRIPTION OF EMBODIMENTS
[0159] Embodiments will next be described in further detail.
Components each having the same function in all drawings for
describing the best modes for carrying out the invention are
respectively given the same reference numerals, and their
repetitive explanations will therefore be omitted.
First Embodiment
Overall Configuration of PLL
[0160] FIG. 1 is a diagram for describing an overall configuration
of a PLL built in a semiconductor integrated circuit according to a
first embodiment of the present invention.
[0161] The PLL according to the first embodiment comprises a phase
frequency detector (PFD) 1, a charge pump (CP) 2, a loop filter
(LP) 3, a selector (SEL) 7, a voltage controlled oscillator (VCO)
8, a divider (DIV) 6, and a calibration adjustment unit 9.
[0162] A reference signal Fref and a feedback signal Fb outputted
from the divider (DIV) 6 are respectively supplied to one input
terminal of the phase frequency detector (PFD) 1 and the other
input terminal thereof to thereby generate a phase-compared signal
from its output. The phase-compared signal of the phase frequency
detector 1 is supplied to the charge pump (CP) 2 to thereby
generate a charge/discharge control signal from its output. The
charge/discharge control signal of the charge pump 2 is supplied to
the loop filter (LP) 3 to thereby generate a filter output signal
from its output.
[0163] The filter output signal outputted from the loop filter (LP)
3, a ground potential GND, a reference voltage V.sub.REF, and a
selection signal S are supplied to the selector (SEL) 7 to thereby
generate a control signal Vc from its output. Namely, in the
selector (SEL) 7, any of the filter output signal, the ground
potential GND and the reference voltage V.sub.REF is selected by
the selection signal S so that the control voltage Vc is generated
from its output. Incidentally, although the selector (SEL) 7 is
coupled between the loop filter (LP) 3 and the voltage controlled
oscillator (VCO) 8 in the first embodimemt, the selector (SEL) 7
can also be coupled between the charge pump 2 and the loop filter
(LP) 3.
[0164] The control voltage Vc outputted from the selector (SEL) 7
is supplied to the voltage controlled oscillator (VCO) 8 so that
the frequency of an oscillation output signal F.sub.vco of its
output is controlled. The oscillation output signal F.sub.vco
outputted from the voltage controlled oscillator 8 is supplied to
the divider (DIV) 6 to thereby generate a feedback signal Fb from
the output of the divider 6. Further, the divider 6 supplies a
division signal to the calibration adjustment unit (LOGIC) 9 in
response to the oscillation output signal F.sub.vco outputted from
the voltage controlled oscillator 8. Incidentally, the frequency of
the division signal is set to a frequency at which a logic circuit
lying inside the calibration adjustment unit (LOGIC) 9 can be
operated.
[0165] The calibration adjustment unit (LOGIC) 9 is supplied with
the reference signal Fref and the division signal outputted from
the divider 6 and generates a selection signal S, a frequency
control sensitivity adjustment signal T, an offset frequency
adjustment signal O and a control signal R. The selection signal S,
the frequency control sensitivity adjustment signal T, the offset
frequency adjustment signal O and the control signal R are utilized
as adjustment signals at a calibration operation. Incidentally, as
a specific example, the calibration adjustment unit (LOGIC) 9 can
be comprised of a central processing unit (CPU) built in the
semiconductor integrated circuit and an operation program which is
operated on the CPU and executes predetermined logical arithmetic
processing. This operation program is stored in a built-in
non-volatile memory of the semiconductor integrated circuit,
whereas information necessary for the logical arithmetic processing
and data or the like about operational results are stored in a
built-in memory of the semiconductor integrated circuit, such as a
RAM or the like.
[0166] Incidentally, the divider (DIV) 6 and the calibration
adjustment unit (LOGIC) 9 have been described in a separate form in
the first embodiment. The divider (DIV) and the calibration
adjustment unit (LOGIC) 9 can, however, also be implemented by
integrated logic hardware.
<<Voltage Controlled Oscillator>>
[0167] FIG. 2 is a diagram showing a configuration of the voltage
controlled oscillator (VCO) 8 included in the PLL according to the
first embodiment of the present invention shown in FIG. 1.
[0168] The voltage controlled oscillator (VCO) 8 shown in FIG. 2
also comprises a voltage-current converter (VIC) 81 and a current
controlled oscillator (CCO) 52 in a manner similar to the voltage
controlled oscillator (VCO) 5 shown in FIG. 26. The current
controlled oscillator (CCO) 52 configured as a ring oscillator
comprises delays 521, 522 and 523 of odd-numbered stages.
Incidentally, although the current controlled oscillator 8 has a
three-stage configuration of delays in FIG. 2, it is needless to
say that it may take a configuration of delays of odd-numbered
stages other than three stages.
[0169] An inverse output signal Fvcob and a non-inverse output
signal Fvco of the delay 523 of the final stage are respectively
supplied to a non-inverse input terminal and an inverse input
terminal of the delay 521 of the first stage. An inverse output
signal and a non-inverse output signal of the delay 521 are
respectively supplied to a non-inverse input terminal and an
inverse input terminal of the delay 522 of the next stage. An
inverse output signal and a non-inverse output signal of the delay
522 are respectively supplied to a non-inverse input terminal and
an inverse input terminal of the delay 523. Incidentally, FIG. 20
is a diagram showing a configuration of each of the delays 521, 522
and 523 of the current controlled oscillator (CCO) 52 in the
voltage controlled oscillator (VCO) 8 shown in FIG. 2.
[0170] When a control voltage (Vc) for controlling the oscillation
frequency of the voltage controlled oscillator (VCO) 8 shown in
FIG. 2 is supplied to its corresponding input terminal of the
voltage-current converter (VIC) 81, the voltage-current converter
(VIC) 81 executes voltage-current conversion to generate a
converted current thereinside. This converted current is converted
to an output voltage (Vp) by the voltage-current converter (VIC)
81. The output voltage (Vp) generated from an output terminal of
the voltage-current converter (VIC) 81 is supplied to the delays
521, 522 and 523 of the current controlled oscillator (CCO) 52 as a
bias voltage so that respective operating currents and delay times
of the delays 521, 522 and 523 are set. The oscillation frequency
of the voltage controlled oscillator (VCO) 8 is therefore
decided.
[0171] In a calibration operation, a reference voltage V.sub.LIM, a
control voltage Vc outputted from the selector (SEL) 7, and a
frequency control sensitivity adjustment signal T and an offset
frequency adjustment signal O outputted from a calibration
adjustment unit (LOGIC) 9 are supplied to the voltage-current
converter (VIC) 81 of the voltage controlled oscillator (VCO) 8
shown in FIG. 8.
<<Configuration of Voltage-Current Converter>>
[0172] FIG. 3 is a diagram showing a configuration of the
voltage-current converter (VIC) 81 included in the voltage
controlled oscillator (VCO) 8 shown in FIG. 2.
[0173] The voltage-current converter (VIC) 81 shown in FIG. 3
comprises a P channel MOS transistor 811, a frequency control
sensitivity trimming N channel MOS transistor 812, a reference
current N channel MOS transistor 813, an offset frequency trimming
N channel MOS transistor 814 and a resistor R.
[0174] The control voltage Vc is supplied to the gate of the
frequency control sensitivity trimming N channel MOS transistor
812, and its gain and drain current Ic can be adjusted by the
frequency control sensitivity adjustment signal T. The reference
current N channel MOS transistor 813 diode-coupled by coupling its
gate and drain is supplied, from the reference voltage V.sub.LIM,
with a reference current Ilim whose current value is set by the
resistor R. A voltage applied between both terminals of the
diode-coupled reference current N channel MOS transistor 813 is
supplied between the gate and source of the offset frequency
trimming N channel MOS transistor 814 that configures a current
mirror along with the diode-coupled reference current N channel MOS
transistor 813. The gain and drain offset current Ir of the offset
frequency trimming N channel MOS transistor 814 can be adjusted by
the offset frequency adjustment signal O. Thus, a control current
Ip that flows through the P channel MOS transistor 811
diode-coupled by coupling its gate and drain becomes a current
Ic+Ir corresponding to the sum of the drain current Ic of the
frequency control sensitivity trimming N channel MOS transistor 812
and the drain offset current Ir of the offset frequency trimming N
channel MOS transistor 814. The total current Ic+Ir is converted to
an output voltage Vp by the P channel MOS transistor 811. The
output voltage Vp is supplied to the delays 521, 522 and 523 of the
current controlled oscillator (CCO) 52 of the voltage controlled
oscillator (VCO) 8 as a bias voltage, so that respective operating
currents and delay times of the delays 521, 522 and 523 are set. An
oscillation frequency of the voltage controlled oscillator (VCO) 8
is therefore determined.
<<Trimming Transistor>>
[0175] FIG. 4 is a diagram showing a configuration of the frequency
control sensitivity trimming N channel MOS transistor 812 included
in the voltage-current converter (VIC) 81 shown in FIG. 3.
[0176] The trimming N channel MOS transistor 812 comprises a
plurality of N channel MOS transistors 8121, 8122 and 8123 whose
drain-source current paths are coupled in parallel, and a plurality
of selectors 8124 and 8125. A gate of the first N channel MOS
transistor 8121 is supplied with the control voltage Vc from the
selector (SEL) 7 of the PLL shown in FIG. 1. A gate of the second N
channel MOS transistor 8122 and a gate of the third N channel MOS
transistor 8123 are respectively supplied with an output signal of
the first selector 8124 and an output signal of the second selector
8125. A first input terminal of the first selector 8124 and a first
input terminal of the second selector 8125 are supplied with the
control voltage Vc of the selector (SEL) 7. A second input terminal
of the first selector 8124 and a second input terminal of the
second selector 8125 are supplied with a ground potential GND.
Further, first and second bits of the frequency control sensitivity
adjustment signal T are respectively supplied to an input selection
terminal of the first selector 8124 and an input selection terminal
of the selector 8125. The first selector 8124 and the second
selector 8125 select one of the control voltage Vc of the selector
(SEL) 7 and the ground potential GND in response to the first and
second bits of the frequency control sensitivity adjustment signal
T and transfers the same to their outputs. Thus, the gain and drain
current Ic of the frequency control sensitivity trimming N channel
MOS transistor 812 can be adjusted in accordance with the frequency
control sensitivity adjustment signal T.
[0177] On the other hand, the offset frequency trimming N channel
MOS transistor 814 included in the voltage-current converter (VIC)
81 shown in FIG. 3 can also be configured by the circuit coupling
as shown in FIG. 4 in a manner similar to the frequency control
sensitivity trimming N channel MOS transistor 812. When the circuit
coupling shown in FIG. 4 is used as the offset frequency trimming N
channel MOS transistor 814, the offset frequency adjustment signal
O is supplied instead of the frequency control sensitivity
adjustment signal T, and a gate-to-source voltage Vgs of the
diode-coupled reference current N channel MOS transistor 813 of the
voltage-current converter (VIC) 81 of FIG. 3 is supplied instead of
the control voltage Vc outputted from the selector (SEL) 7. In
doing so, the gain and drain current Ir of the offset frequency
trimming N channel MOS transistor 814 can be adjusted in accordance
with the offset frequency adjustment signal O.
<<Selector inside trimming transistor>>
[0178] FIG. 19 is a diagram showing a configuration of each of the
selectors 8124 and 8125 included in the frequency control
sensitivity trimming N channel MOS transistor 812 shown in FIG.
4.
[0179] The selector 8124 (8125) shown in FIG. 19 comprises a CMOS
inverter 81244, N channel MOS transistors 81241 and 81243 and a P
channel MOS transistor 81242.
[0180] When the frequency control sensitivity adjustment signal T
is high in level, the N channel MOS transistor 81241 is turned on
so that the output of the CMOS inverter 81244 is brought to a low
level. Thus, the P channel MOS transistor 81242 is turned on and
the N channel MOS transistor 81243 is turned off. Accordingly, at
this time, the control voltage Vc is transferred to an output Out
via the N channel MOS transistor 81241 and the P channel MOS
transistor 81242. When the frequency control sensitivity adjustment
signal T is low in level, the N channel MOS transistor 81241 is
turned off so that the output of the CMOS inverter 81244 is brought
to a high level. Thus, the P channel MOS transistor 81242 is turned
off and the N channel MOS transistor 81243 is turned on.
Accordingly, at this time, the output Out is brought to a ground
potential GND by the N channel MOS transistor 81242 placed in the
on state.
<<Operation of Voltage-Current Converter>>
[0181] The operation of the voltage-current converter (VIC) 81
shown in FIG. 3 will next be explained.
[0182] Since the frequency control sensitivity trimming N channel
MOS transistor 812 is in an off state when the control voltage Vc
of the selector (SEL) 7 is zero volts, the drain current Ic is
zero.
[0183] On the other hand, since the reference voltage V.sub.LIM is
of a reference voltage generated from a reference voltage
generating circuit such as a bandgap reference (BGR) or the like,
the value of the reference current Ilim set by the resistor R
becomes a constant value without depending on the control voltage
Vc. Thus, assuming that the current mirror ratio between the
reference current N channel MOS transistor 813 and the offset
frequency trimming N channel MOS transistor 814 is assumed to be
1:N, the drain offset current Ir of the offset frequency trimming N
channel MOS transistor 814 becomes Ir=N*Ilim. Here, the current
mirror ratio N between the reference current N channel MOS
transistor 813 and the offset frequency trimming N channel MOS
transistor 814 can be adjusted in response to the offset frequency
adjustment signal O. Thus, when the value of the offset frequency
adjustment signal O increases, the value of the drain offset
current Ir also increases. Further, the value of the control
current Ip given from the relationship of Ip=Ic+Ir also
increases.
[0184] FIG. 32 is a diagram for describing the operation of the
voltage-current converter (VIC) 81 shown in FIG. 3.
[0185] Since the drain offset current Ir also increases when the
value of the offset frequency adjustment signal O increases in a
range of 0 to 3 as shown in FIG. 32, the value of a control current
Ip at the control voltage Vc=0 increases.
[0186] When the control voltage (Vc) increases more than a
threshold voltage Vthn of the frequency control sensitivity
trimming N channel MOS transistor 812, the drain current Ic thereof
increases from zero. Since the control current Ip is given based on
the relationship of Ip=Ic+Ir, the value of the control current Ip
also increases as the control voltage Vc increases more than the
threshold voltage Vthn of the frequency control sensitivity
trimming N channel MOS transistor 812.
[0187] Namely, assuming that the conductance of the frequency
control sensitivity trimming N channel MOS transistor 812 is gm,
the drain current Ic of the frequency control sensitivity trimming
N channel MOS transistor 812 is given in accordance with the
relationship of Ic=m*Vc. Thus, when the control voltage Vc
increases in a region in which the control voltage Vc is higher
than the threshold voltage Vthn of the frequency control
sensitivity trimming N channel MOS transistor 812 as shown in FIG.
32, the value of the control current Ip also increases.
[0188] The conductance gm of the frequency control sensitivity
trimming N channel MOS transistor 812 can be adjusted by the value
of the frequency control sensitivity adjustment signal T. Namely,
as shown in FIG. 4, the rate of activation of the N channel MOS
transistors 8121, 8122 and 8123 lying inside the frequency control
sensitivity trimming N channel MOS transistor 812 can be adjusted
by the value of the frequency control sensitivity adjustment signal
T. When the value of the frequency control sensitivity adjustment
signal T increases, the activation rate, the conductance gm of the
frequency control sensitivity trimming N channel MOS transistor 812
and the drain current Ic increase.
[0189] FIG. 33 is a diagram for describing the operation of the
voltage-current converter (VIC) 81 shown in FIG. 3.
[0190] In the region in which the control voltage Vc is higher than
the threshold voltage Vthn of the frequency control sensitivity
trimming N channel MOS transistor 812 as shown in FIG. 33, the
conductance gm and drain current Ic of the frequency control
sensitivity trimming N channel MOS transistor 812 increase as the
value of the frequency control sensitivity adjustment signal T
increases. Therefore, the value of the control current Ip given in
the relational expression of Ip=Ic+Ir also increases.
[0191] The PLL of the first embodiment shown in FIG. 1, which has
been described above, includes the calibration operating period and
the normal operating period. During the first calibration operating
period, the PLL is controlled to the open loop, so that the
frequency characteristic of the voltage controlled oscillator (VCO)
8 is adjusted to a desired characteristic by the calibration
adjustment unit (LOGIC) 9. During the normal operation period after
the calibration operation, the PLL is controlled to the closed
loop, so that the phase and frequency of the output signal of the
divider (DIV) 6 responsive to the output signal of the voltage
controlled oscillator (VCO) 8 of the PLL respectively coincide with
the phase and frequency of the reference signal supplied to the
phase detector (PFD) 1, thereby enabling a lock operation of the
PLL.
<<Calibration Operation>>
[0192] The calibration operation will next be explained in
detail.
[0193] The calibration operation to be described below is
automatically started by the calibration adjustment unit (LOGIC) 9
when the supply of an operating source voltage to the semiconductor
integrated circuit with the PLL built therein is started by the
first embodiment of the present invention shown in FIG. 1, for
example. With the calibration operation, an adjustment value for
setting the built-in PLL to the desired characteristic is acquired
and the so-acquired adjustment value is stored in the built-in
memory of the semiconductor integrated circuit such as RAM or the
like. When the calibration operation is completed in this way, the
calibration adjustment unit (LOGIC) 9 automatically switches the
operation of the PLL built-in semiconductor integrated circuit to
the normal operation.
[0194] During the period of the calibration operation, the PLL
according to the first embodiment of the present invention shown in
FIG. 1 is controlled to the open loop, so that the frequency
control sensitivity adjustment signal T and the offset frequency
adjustment signal O are updated until the frequency characteristic
of the voltage controlled oscillator (VCO) 8 reaches the desired
characteristic. The frequency characteristic of the voltage
controlled oscillator (VCO) 8 of the PLL controlled to the open
loop is monitored and the updating thereof is stopped when the
frequency characteristic is brought to the desired characteristic,
whereby the calibration operation is completed.
[0195] FIG. 5 is a diagram for describing the calibration operation
of the PLL according to the first embodiment of the present
invention shown in FIG. 1.
[0196] Since the selection signal S becomes S="1" at Step 51 when
the calibration operation of the PLL shown in FIG. 1 is started,
the selector (SEL) 7 of the PLL shown in FIG. 1 selects a ground
potential GND corresponding to an input as a control voltage Vc
corresponding to an output. Since, at this time, the phase
frequency detector (PFD) 1 and the charge pump (CP) 2 are
respectively controlled to a standby state by a control signal R
high in level, the PLL is controlled to an open loop. At this time,
the frequency control sensitivity adjustment signal T and the
offset frequency adjustment signal O are respectively set to T="0"
and O="0". In this initial state, the calibration adjustment unit
(LOGIC) 9 starts counting a divided signal of an output signal
(Fvco) of the voltage controlled oscillator (VCO) 8 by the divider
(DIV) 6 at Step 52.
[0197] The calibration adjustment unit (LOGIC) 9 compares a count
result N1 of the output signal (Fvco) with a target value A at Step
53. Incidentally, the target value A corresponds to an offset
frequency corresponding to one target frequency characteristic of
the voltage controlled oscillator (VCO) 8. When the calibration
adjustment unit (LOGIC) 9 determines that N1 and A are expressed in
a relationship of N1<A, the calibration adjustment unit (LOGIC)
9 updates the offset frequency adjustment signal O to O=0+1 at Step
54.
[0198] The frequency of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 increases in response to the control
voltage Vc corresponding to the ground potential GND selected by
the selector (SEL) 7 and the updated offset frequency adjustment
signal O. There is a possibility that an increase in the frequency
of the output signal (Fvco) will be insufficient at first and the
determination as to the relationship of N1<A will continue at
Step 53. There is a possibility that the updating of the offset
frequency adjustment signal O at Step 54 will continue. However,
the increase in the frequency of the output signal (Fvco) becomes
sufficient gradually and the relationship of N1>A is determined
at Step 53.
[0199] FIG. 6 is a diagram showing the manner in which the offset
frequency of an output signal (Fvco) of the voltage controlled
oscillator (VCO) 8 increases in response to the updating of an
offset frequency adjustment signal O in the calibration operation
of the PLL according to the first embodiment of the present
invention shown in FIG. 1.
[0200] Since a relationship of N1>A targeted when the updated
value of the offset frequency adjustment signal O is "2" is first
determined in the example of FIG. 6, the final updated value of the
offset frequency adjustment signal O is set to "2". Namely, at Step
55, the calibration adjustment unit (LOGIC) 9 sets the offset
frequency adjustment signal O to the final updated value "2"
(O=ON1>A hold) and changes the selection signal S from S="1" to
S="2".
[0201] When the calibration of the offset frequency adjustment
signal O of the voltage controlled oscillator (VCO) 8 is completed
in this way, the calibration operation proceeds to the calibration
of the frequency control sensitivity adjustment signal T.
[0202] First, the selector (SEL) 7 of the PLL shown in FIG. 1
switches an input ground potential GND to a reference voltage
V.sub.REF as an output control voltage Vc in response to the change
of the selection signal S from S="1" to S="2". At this time, the
frequency control sensitivity adjustment signal T is initially set
to T="0". The frequency of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 slightly increases in response to the
change of the control voltage Vc supplied from the selector (SEL) 7
of the PLL shown in FIG. 1 to the voltage controlled oscillator
(VCO) 8 from the ground potential GND to the reference voltage
V.sub.REF.
[0203] In this initial condition, the calibration adjustment unit
(LOGIC) 9 starts counting a divided signal of the output signal
(Fvco) of the voltage controlled oscillator (VCO) 8 by the divider
(DIV) 6 at Step 56. The calibration adjustment unit (LOGIC) 9
compares a count result N2 of the output signal (Fvco) with a
target value B at Step 57. Incidentally, the target value B
corresponds to frequency control sensitivity corresponding to
another target frequency characteristic of the voltage controlled
oscillator (VCO) 8. When the calibration adjustment unit (LOGIC) 9
determines a relationship of N2<B at Step 57, it updates the
frequency control sensitivity adjustment signal T to T=T+1 at Step
58.
[0204] The frequency of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 increases in response to the increase
and updating of the frequency control sensitivity adjustment signal
T. There is a possibility that an increase in the frequency will be
insufficient at first and the determination as to the relationship
of N2<B at Step 57 will continue. There is a possibility that
the updating of the frequency control sensitivity adjustment signal
T at Step 58 will continue. However, the increase in the frequency
becomes sufficient gradually and the relationship of N2>B is
determined at Step 57.
[0205] FIG. 7 is a diagram showing the manner in which the
frequency of an output signal (Fvco) of the voltage controlled
oscillator (VCO) 8 increases in response to the updating of a
frequency control sensitivity adjustment signal T in the
calibration operation of the PLL according to the first embodiment
of the present invention shown in FIG. 1.
[0206] Since a relationship of N2>B targeted when the updated
value of the frequency control sensitivity adjustment signal T is
"2" is first determined in the example of FIG. 7, the final updated
value of the frequency control sensitivity adjustment signal T is
set to "2". Namely, at Step 59, the calibration adjustment unit
(LOGIC) 9 sets the frequency control sensitivity adjustment signal
T to the final updated value "2" (T=T@N2>B hold) and restores
the selection signal S from S="2" to S="0". Since, at this time,
the calibration adjustment unit (LOGIC) 9 restores the control
signal R from a high level to a low level, the phase frequency
detector (PFD) 1 and the charge pump (CP) 2 are controlled to an
active state in response to the control signal R low in level.
Therefore, the PLL is controlled to a closed loop. In response to
the selection signal S="0", the selector (SEL) 7 switches the input
reference voltage V.sub.REF to the output signal of the loop filter
(LP) 3 as the output's control voltage Vc. Thus, the PLL is brought
to the normal operating period corresponding to the closed loop, so
that the phase and frequency of the output signal of the divider
(DIV) 6 responsive to the output signal of the voltage controlled
oscillator (VCO) 8 of the PLL respectively coincide with the phase
and frequency of the reference signal Fref, thereby enabling a lock
operation of the PLL.
[0207] Thus, the calibration of the offset frequency adjustment
signal O of the voltage controlled oscillator (VCO) 8 in the PLL
and the calibration of the frequency control sensitivity adjustment
signal T can be executed by the calibration operation shown in FIG.
5. Incidentally, the value of the reference voltage V.sub.REF is
set extremely close to the value of the control voltage Vc supplied
from the loop filter (LP) 3 to the voltage controlled oscillator 8
for the PLL lock operation during the normal operating period of
the PLL. Namely, the frequency fvco of the output signal (Fvco) of
the voltage controlled oscillator (VCO) 8 during the normal
operating period of the PLL according to the first embodiment of
the present invention shown in FIG. 1 is given in terms of a
relational expression of fvco=N*fref assuming that the division
ratio of the divider (DIV) 6 is N and the frequency of the
reference signal Fref is fref. Thus, the reference voltage
V.sub.REF set extremely close to the value of such a control
voltage Vc as to obtain the oscillation output signal (Fvco) having
the frequency fvco given in this relational expression, is supplied
to the voltage controlled oscillator 8 during the period of the
calibration operation.
[0208] FIG. 34 is a diagram showing a frequency characteristic L1
of the voltage controlled oscillator (VCO) 5 examined prior to the
present invention by the present inventors et al., which includes
the voltage-current converter (VIC) 51 of FIG. 27 and has been
shown in FIG. 26, and a frequency characteristic L2 of the voltage
controlled oscillator (VCO) 8 according to the first embodiment of
the present invention, which has been described in FIGS. 1 through
7 and FIGS. 32 and 33.
[0209] The control voltages V.sub.REF for generating the target
oscillation frequencies Fvco of both voltage controlled oscillators
(VCO) 5 and 8 are supplied to VCO. The threshold voltages of the N
channel MOS transistors 812 and 511 supplied with the control
voltages Vc at the voltage-current converters (VIC) 81 and 51 shown
in FIGS. 3 and 27 are assumed to be Vthn. Further, the offset
frequency of the voltage controlled oscillator (VCO) 8 adjusted by
the calibration operation according to the first embodiment of the
present invention is assumed to be Fof. Incidentally, the value of
the control voltage V.sub.REF is set extremely close to the value
of the control voltage Vc supplied from the loop filter (LP) 3 to
the voltage controlled oscillator for the lock operation of the PLL
during the normal operating period of the PLL.
[0210] As shown in the frequency characteristic L1 of FIG. 34, the
frequency control sensitivity Kv of the voltage controlled
oscillator (VCO) 5 examined prior to the present invention by the
present inventors et al. has been given in the relational
expression of Kv=Fvco/(V.sub.REF-Vthn) and was extremely high
frequency control sensitivity Kv. As a result, a problem arose in
that since the oscillation output frequency of the VCO fluctuated
greatly due to noise contained in the control voltage Vc, a
satisfactory jitter characteristic was not obtained.
[0211] As shown in the frequency characteristic L2 of FIG. 34
contrary to it, the frequency control sensitivity Kv of the voltage
controlled oscillator (VCO) 8 according to the first embodiment of
the present invention is given in the relational expression of
Kv=(Fvco-Fof)/(V.sub.REF-Vthn) and becomes relatively low frequency
control sensitivity Kv. Thus, since the oscillation output
frequency of the VCO does not fluctuate greatly due to noise
contained in the control voltage Vc, a satisfactory jitter
characteristic can be obtained. Further, undesired band widening of
the PLL can also be reduced.
[0212] Thus, according to the first embodiment of the present
invention, it is possible to mitigate the problem that the
frequency control sensitivity Kv becomes large due to a low
threshold voltage and a low source voltage based on the adoption of
a miniaturized manufacturing process. The calibration operation
according to the first embodiment of the present invention makes it
possible to set the frequency control sensitivity Kv to a target
value with a high degree of accuracy without being set to an
extremely low value.
Second Embodiment
[0213] FIG. 8 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a second
embodiment of the present invention.
[0214] Incidentally, the second embodiment of the present invention
shown in FIG. 8 corresponds to a modification of the first
embodiment of the present invention. The PLL shown in FIG. 8
differs from the PLL shown in FIG. 1 in that the function of
causing a selector (SEL) 7 to select a second reference voltage
V.sub.REF2 in response to a selection signal S="3" is added to the
function of causing the selector (SEL) 7 to select an output signal
of a loop filter (LP) 3, a ground potential GND and a first
reference voltage V.sub.REF1 as an output control voltage Vc in
response to selection signals S="0", "1" and "2" respectively.
[0215] A calibration operation will next be explained in
detail.
[0216] During the calibration operation, the PLL according to the
second embodiment of the present invention shown in FIG. 8 is
controlled to an open loop in a manner similar to the first
embodiment, so that a frequency control sensitivity adjustment
signal T and an offset frequency adjustment signal O are updated
until a frequency characteristic of a voltage controlled oscillator
(VCO) 8 is brought to a desired characteristic. The frequency
characteristic of the voltage controlled oscillator (VCO) 8 of the
PLL controlled to the open loop is monitored and the updating
thereof is stopped when the frequency characteristic is brought to
the desired characteristic, whereby the calibration operation is
completed.
[0217] FIG. 9 is a diagram for describing the calibration operation
of the PLL according to the second embodiment of the present
invention shown in FIG. 8.
[0218] Since the selection signal S becomes S="1" at Step 90 when
the calibration operation of the PLL shown in FIG. 8 is started,
the selector (SEL) 7 of the PLL shown in FIG. 8 selects an input
ground potential GND as an output control voltage Vc. Since, at
this time, a phase frequency detector (PFD) 1 and a charge pump
(CP) 2 are respectively controlled to a standby state by a control
signal R high in level, the PLL is controlled to an open loop. At
this time, the frequency control sensitivity adjustment signal T
and the offset frequency adjustment signal O are respectively set
to T="0" and O="0". In this initial state, a calibration adjustment
unit (LOGIC) 9 starts counting a divided signal of an output signal
(Fvco) of the voltage controlled oscillator (VCO) 8 by a divider
(DIV) 6 at Step 91.
[0219] The calibration adjustment unit (LOGIC) 9 compares a count
result N1 of the output signal (Fvco) with a target value A at Step
92. Incidentally, the target value A corresponds to an offset
frequency corresponding to one target frequency characteristic of
the voltage controlled oscillator (VCO) 8. When the calibration
adjustment unit (LOGIC) 9 determines that N1 and A are expressed in
a relationship of N1<A, the calibration adjustment unit (LOGIC)
9 updates the offset frequency adjustment signal O to O=0+1 at Step
93.
[0220] The frequency of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 increases in response to the control
voltage Vc corresponding to the ground potential GND selected by
the selector (SEL) 7 and the updated offset frequency adjustment
signal O. There is a possibility that an increase in the frequency
of the output signal (Fvco) will be insufficient at first and the
determination as to the relationship of N1<A will continue at
Step 92. There is a possibility that the updating of the offset
frequency adjustment signal O at Step 93 will continue. However,
the increase in the frequency of the output signal (Fvco) becomes
sufficient gradually and the relationship of N1>A is determined
at Step 92.
[0221] FIG. 10 is a diagram showing the manner in which the offset
frequency of an output signal (Fvco) of the voltage controlled
oscillator (VCO) 8 increases in response to the updating of an
offset frequency adjustment signal O in the calibration operation
of the PLL according to the second embodiment of the present
invention shown in FIG. 8.
[0222] Since a relationship of N1>A targeted when the updated
value of the offset frequency adjustment signal O is "2" is first
determined even in the example of FIG. 10, the final updated value
of the offset frequency adjustment signal O is set to "2". Namely,
at Step 94, the calibration adjustment unit (LOGIC) 9 sets the
offset frequency adjustment signal O to the final updated value "2"
(O=ON1>A hold) and changes the selection signal S from S="1" to
S="2".
[0223] When the calibration of the offset frequency adjustment
signal O of the voltage controlled oscillator (VCO) 8 is completed
in this way, the calibration operation proceeds to the calibration
of the frequency control sensitivity adjustment signal T.
[0224] First, the selector (SEL) 7 of the PLL shown in FIG. 8
switches an input ground potential GND to a first reference voltage
V.sub.REF1 as an output control voltage Vc in response to the
change of the selection signal S from S="1" to S="2". At this time,
the frequency control sensitivity adjustment signal T is initially
set to T="0". The frequency of the output signal (Fvco) of the
voltage controlled oscillator (VCO) 8 slightly increases in
response to the change of the control voltage Vc supplied from the
selector (SEL) 7 of the PLL shown in FIG. 8 to the voltage
controlled oscillator (VCO) 8 from the ground potential GND to the
first reference voltage V.sub.REF1. In this condition, the
calibration adjustment unit (LOGIC) 9 starts counting a divided
signal of the output signal (Fvco) of the voltage controlled
oscillator (VCO) 8 by the divider (DIV) 6 at Step 95 and stores a
count result N2 in a built-in memory of the semiconductor
integrated circuit.
[0225] Next, the calibration adjustment unit (LOGIC) 9 changes the
selection signal S from S="2" to S="3" at Step 96. In doing so, the
selector (SEL) 7 of the PLL shown in FIG. 8 switches the input
first reference voltage V.sub.REF1 to a second reference voltage
V.sub.REF2 slightly higher in level than it as the output control
voltage Vc in response to the change of the selection signal S from
S="2" to S="3". The frequency of the output signal (Fvco) of the
voltage controlled oscillator (VCO) 8 slightly increases in
response to the change of the control voltage Vc supplied to the
voltage controlled oscillator (VCO) 8 from the first reference
voltage V.sub.REF1 to the second reference voltage V.sub.REF2. In
this state, the calibration adjustment unit (LOGIC) 9 starts
counting a divided signal of the output signal (Fvco) of the
voltage controlled oscillator (VCO) 8 by the divider (DIV) 6 at
Step 96 and stores a count result N3 in the built-in memory of the
semiconductor integrated circuit.
[0226] Next, at Step 97, the calibration adjustment unit (LOGIC) 9
compares the count result N3 of the output signal (Fvco) with a
target value B and further compares a difference N3-N2 between the
count result N3 and the count result N2 with a target value C.
Incidentally, the target value B with the target value C
respectively correspond to a VCO oscillation frequency and AC
frequency control sensitivity each corresponding to a target
frequency characteristic of the voltage controlled oscillator (VCO)
8. The VCO oscillation frequency indicates the oscillation
frequency of the voltage controlled oscillator (VCO) 8 where the
control voltage Vc is set to a predetermined value, whereas the AC
frequency control sensitivity indicates control sensitivity of a
width of change in the oscillation frequency of the voltage
controlled oscillator (VCO) 8 when the control voltage Vc changes
in a predetermined range. When the calibration adjustment unit
(LOGIC) 9 determines at Step 97 that the count result and the
target value are expressed in a relationship of N3<B or a
relationship of N3-N2<C, the frequency control sensitivity
adjustment signal T is updated to T=T+1 at Step 98.
[0227] The frequency of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 increases in response to the increase
and updating of the frequency control sensitivity adjustment signal
T. There is a possibility that an increase in the frequency will be
insufficient at first and the determination as to the relationship
of N3<B or the relationship of N3-N2<C at Step 97 will
continue. There is a possibility that the updating of the frequency
control sensitivity adjustment signal T at Step 98 will continue.
However, the increase in the frequency becomes sufficient gradually
and the relationship of N3>B and the relationship of N3-N2>C
are determined at Step 97.
[0228] FIG. 11 is a diagram showing the manner in which the
frequency of an output signal (Fvco) of the voltage controlled
oscillator (VCO) 8 increases in response to the updating of a
frequency control sensitivity adjustment signal T in the
calibration operation of the PLL according to the second embodiment
of the present invention shown in FIGS. 8 and 9.
[0229] Since a relationship of N3>B and a relationship of
N3-N2>C targeted when the updated value of the frequency control
sensitivity adjustment signal T is "2" are first determined in the
example of FIG. 11, the final updated value of the frequency
control sensitivity adjustment signal T is set to "2". Namely, at
Step 99, the calibration adjustment unit (LOGIC) 9 sets the
frequency control sensitivity adjustment signal T to the final
updated value "2" (T=TN3>B and N3-N2>C hold) and restores the
selection signal S from S="2" to S="0". Since, at this time, the
calibration adjustment unit (LOGIC) 9 restores the control signal R
from a high level to a low level, the phase frequency detector
(PFD) 1 and the charge pump (CP) 2 are controlled to an active
state in response to the control signal R low in level. Therefore,
the PLL is controlled to a closed loop. In response to the
selection signal S="0", the selector (SEL) 7 switches the input
reference voltage V.sub.REF to the output signal of the loop filter
(LP) 3 as the output's control voltage Vc. Thus, the PLL is brought
to the normal operating period corresponding to the closed loop, so
that the phase and frequency of the output signal of the divider
(DIV) 6 responsive to the output signal of the voltage controlled
oscillator (VCO) 8 of the PLL respectively coincide with the phase
and frequency of the corresponding reference signal Fref, thereby
enabling a lock operation of the PLL.
[0230] Thus, the calibration of the offset frequency adjustment
signal O of the voltage controlled oscillator (VCO) 8 in the PLL
and the calibration of the frequency control sensitivity adjustment
signal T can be executed by the calibration operation shown in FIG.
9. Incidentally, the value of the first reference voltage
V.sub.REF1 and the value of the second reference voltage V.sub.REF2
are set extremely close to the value of the control voltage Vc
supplied from the loop filter (LP) 3 to the voltage controlled
oscillator for the PLL lock operation during the normal operating
period of the PLL. Namely, the frequency fvco of the output signal
(Fvco) of the voltage controlled oscillator (VCO) 8 during the
normal operating period of the PLL according to the second
embodiment of the present invention shown in FIG. 8 is given in a
relational expression of fvco=N*fref assuming that the division
ratio of the divider (DIV) 6 is N and the frequency of the
reference signal Fref is fref. Thus, the first reference voltage
V.sub.REF1 and the second reference voltage V.sub.REF2 each set
extremely close to the value of such a control voltage Vc as to
obtain the oscillation output signal (Fvco) having the frequency
fvco given in this relational expression, are supplied to the
voltage controlled oscillator 8 during the period of the
calibration operation.
[0231] As is understood from FIG. 11, the calibration operation of
the PLL according to the second embodiment of the present invention
is of a method for accurately adjusting the frequency control
sensitivity of the voltage controlled oscillator (VCO) 8 between
the first reference voltage V.sub.REF1 and the second reference
voltage V.sub.REF2 each set extremely close to the value of the
control voltage Vc supplied during the normal operating period of
the PLL.
[0232] In contrast to this, although the calibration operation of
the PLL according to the first embodiment of the present invention
is relatively simple, it is not possible to compensate for
fluctuations in the AC frequency control sensitivity due to
fluctuations in the threshold voltage Vthn of the N channel MOS
transistor 812 supplied with the control voltage Vc at the
voltage-current converter (VIC) 81 shown in FIG. 3 as is understood
from FIG. 7.
[0233] On the other hand, since the relationship of N3-N2>C is
maintained between the first reference voltage V.sub.REF1 and the
second reference voltage V.sub.REF2 as shown in FIG. 11 in the
calibration operation of the PLL according to the second embodiment
of the present invention, it is possible to compensate for the
fluctuations in the AC frequency control sensitivity. Namely, it is
possible to compensate for the fact that the AC frequency control
sensitivity has the value of Kv=C/(V.sub.REF2-V.sub.REF1) between
the first reference voltage V.sub.REF1 and the second reference
voltage V.sub.REF2.
Third Embodiment
[0234] FIG. 12 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a third
embodiment of the present invention.
[0235] The PLL shown in FIG. 12 is different from the PLL shown in
FIG. 1 in that the function of selection of a selector (SEL) 7 is
changed in such a manner that it selects a first reference voltage
V.sub.REF1 and a second reference voltage V.sub.REF2 without
causing the selector (SEL) 7 to select the ground potential GND and
the reference voltage V.sub.REF as the output control voltage Vc in
response to the selection signals S="1" and "2".
[0236] Further, in the PLL shown in FIG. 12, three adjustment
signals T, L and G are supplied from a calibration adjustment unit
(LOGIC) 9 to a voltage controlled oscillator (VCO) 8 without the
voltage controlled oscillator (VCO) 8 being supplied with the
frequency control sensitivity adjustment signal T and the offset
frequency adjustment signal O as in the case of the PLL shown in
FIG. 1. Correspondingly, a configuration of the voltage controlled
oscillator (VCO) 8 of the PLL shown in FIG. 12 is also changed.
[0237] FIG. 13 is a diagram showing the configuration of the
voltage controlled oscillator (VCO) 8 included in the PLL according
to the third embodiment of the present invention shown in FIG.
12.
[0238] The voltage controlled oscillator (VCO) 8 shown in FIG. 13
also comprises a voltage-current converter (VIC) 81 and a current
controlled oscillator (CCO) 52 in a manner similar to the voltage
controlled oscillator (VCO) 5 shown in FIG. 2. The current
controlled oscillator (CCO) 52 configured as a ring oscillator
comprises delays of odd-numbered stages 521, 522 and 523 identical
in configuration to the current controlled oscillator (CCO) 52
shown in FIG. 2.
[0239] The voltage-current converter (VIC) 81 whose input terminal
is supplied with a control voltage (Vc) for controlling the
oscillation frequency of the voltage controlled oscillator (VCO) 8
shown in FIG. 13 can be supplied with adjustment signals T, L and G
from the calibration adjustment unit (LOGIC) 9.
[0240] FIG. 14 is a diagram showing a configuration of the
voltage-current converter (VIC) 81 included in the voltage
controlled oscillator (VCO) 8 shown in FIG. 13. The configuration
of the voltage-current converter (VIC) 81 shown in FIG. 14 is
equivalent to one noticeably changed from the configuration of the
voltage-current converter (VIC) 81 shown in FIG. 3.
[0241] Namely, the voltage-current converter (VIC) 81 shown in FIG.
14 comprises five P channel MOS transistors 81p1 through 81p5 and
six N channel MOS transistors 81n1 through 81n6. The control
voltage Vc is supplied to gates of the two N channel MOS
transistors 81n1 and 81n6 in parallel. The gains and drain currents
Ic of the two N channel MOS transistors 81n1 and 81n6 can be
adjusted by the adjustment signal T.
[0242] The N channel MOS transistor 81n2 diode-coupled by coupling
its gate and drain is supplied with a reference current Ilim whose
current value is set by a resistor R, from a reference voltage
V.sub.LIM. A gate of the N channel MOS transistor 81n3 is coupled
to its corresponding gate and drain of the N channel MOS transistor
81n2 so as to configure a current mirror along with the
diode-coupled N channel MOS transistor 81n2. The gain and drain
current of the N channel MOS transistor 81n3 can be adjusted by the
adjustment signal L. A drain of the N channel MOS transistor 81n3
is supplied with the drain current Ic of the N channel MOS
transistor 81n1 via a current mirror configured by the two P
channel MOS transistors 81p1 and 81p2.
[0243] The N channel MSO transistor 81n4 diode-coupled by its
gate-drain coupling is coupled to its corresponding drain of the N
channel MOS transistor 81n3. A current corresponding to a
difference between the drain current of the P channel MOS
transistor 81p2 and the drain current of the N channel MOS
transistor 81n3 flows into the diode-coupled N channel MOS
transistor 81n4. A gate of the N channel MOS transistor 81n5 is
coupled to its corresponding gate and drain of the N channel MOS
transistor 81n4 so as to configure a current mirror along with the
diode-coupled N channel MOS transistor 81n4.
[0244] A drain current of the N channel MOS transistor 81n5 is
supplied to its corresponding drain of the N channel MOS transistor
81n6 via a current mirror configured by the two P channel MOS
transistors 81p3 and 81p4. The gain and drain current of the P
channel MOS transistor 81p4 can be adjusted by the adjustment
signal G. The P channel MOS transistor 81p5 diode-coupled by its
gate-drain coupling is coupled between the drain of the N channel
MOS transistor 81n6 and a source voltage V.sub.DD. A control
current Ip that flows through the diode-coupled P channel MOS
transistor 81p5 becomes a current corresponding to a difference
between the drain current of the P channel MOS transistor 81p4 and
the drain current of the N channel MOS transistor 81n6. This
difference current is converted to an output voltage Vp by the
diode-coupled P channel MOS transistor 81p5. The output voltage Vp
is supplied to the delays 521, 522 and 523 of the current
controlled oscillator (CCO) 52 of the voltage controlled oscillator
(VCO) 8 as a bias voltage, so that respective operating currents
and delay times of the delays 521, 522 and 523 are set, thereby
determining the oscillation frequency of the voltage controlled
oscillator (VCO) 8.
[0245] The operation of the voltage-current converter (VIC) 81
shown in FIG. 14 will next be described.
[0246] The drain current Ic of the N channel MOS transistor 81n1
whose gate is supplied with the control voltage Vc is supplied to
the drain of the N channel MOS transistor 81n3 via a current mirror
having a current mirror ratio of 1:1, which has been configured by
the two P channel MOS transistors 81p1 and 81p2. On the other hand,
since the current mirror ratio between the N channel MOS
transistors 81n2 and 81n3 is set to 1:NL, the drain current of the
N channel MOS transistor 81n3 becomes NL*Ilim. Thus, the current
Ic-NL*Ilim corresponding to the difference between the drain
current Ic of the P channel MOS transistor 81p2 and the drain
current NL*Ilim of the N channel MOS transistor 81n3 flows into the
diode-coupled N channel MOS transistor 81n4.
[0247] Since the current mirror ratio between the N channel MOS
transistors 81n4 and 81n5 is set to 1:1, the drain current of the N
channel MOS transistor 81n5 is brought to Ic-NL*Ilim. On the other
hand, since the current mirror ratio between the P channel MOS
transistors 81p3 and 81p4 is set to 1:NG, the drain current of the
P channel MOS transistor 81p4 becomes NG*(Ic-NL*Ilim). The drain
current Ic flows through the N channel MOS transistor 81n6 whose
gate is supplied with the control voltage Vc. Thus, the control
current Ip that flows through the diode-coupled P channel MOS
transistor 81p5 is brought to the current (NG-1)*Ic-NL*Ilim
corresponding to the difference between the drain current
NG*(Ic-NL*Ilim) of the P channel MOS transistor 81p4 and the drain
current Ic of the N channel MOS transistor 81n6.
[0248] FIG. 35 is a diagram showing the dependence of the control
current Ip flowing through the P channel MOS transistor 81p5 on the
control voltage Vc at the voltage-current converter (VIC) 81 shown
in FIG. 14.
[0249] Since the two N channel MOS transistors 81n1 and 81n6 are
off when the control voltage Vc is lower in level than the
threshold voltages Vthn of the two N channel MOS transistors 81n1
and 81n6 whose gates are supplied with the control voltage Vc,
their drain currents Ic are zero. On the other hand, since the
gates of the N channel MOS transistors 81n4 and 81n5 configuring
the current mirror are pulled down to the ground potential GND by
the drain current NL*Ilim of the N channel MOS transistor 81n3, the
drain current of the N channel MSO transistor 81n5 also becomes
zero. Thus, since the drain currents of the P channel MOS
transistors 81p3 and 81p4 that configure the current mirror are
also brought to zero, the control current Ip that flows through the
diode-coupled P channel MOS transistor 81p5 also becomes zero.
[0250] When the threshold voltages Vthn of the N channel MOS
transistors 81n1 and 81n6 and the control voltage Vc become equal
to each other, the N channel MOS transistors 81n1 and 81n6 are
turned on so that their drain currents Ic become a small value
respectively. Thus, since the drain currents Ic of the P channel
MOS transistors 81p1 and 81p2 also become a small value
respectively, the drain current NL*Ilim of the N channel MOS
transistor 81n3 becomes a value larger than the small drain current
Ic of the P channel MSO transistor 81p2. As a result, the gates of
the N channel MSO transistors 81n4 and 81n5 are pulled down to the
ground potential GND so that the drain current of the N channel MOS
transistor 81n5 also becomes zero. Thus, since the drain currents
of the P channel MOS transistors 81p3 and 81p4 also become zero,
the control current Ip that flows through the diode-coupled P
channel MOS transistor 81p5 is determined by the small drain
current Ic of the N channel MOS transistor 81n6. In this case, the
dependence of the drain current Ic of the N channel MOS transistor
81n6 and the control current Ip flowing through the P channel MOS
transistor 81p5 on the control voltage Vc can be adjusted by the
value of the adjustment signal T. Since the conductances gm of the
N channel MOS transistors 81n1 and 81n6 also become large as the
value of the adjustment signal T becomes large, the value of the
drain current Ic of the N channel MOS transistor 81n6 and the value
of the control current Ip flowing through the P channel MOS
transistor 81p5 also increase.
[0251] When the control voltage Vc increases than the values of the
N channel MOS transistors 81n1 and 81n6, the degrees of conduction
of the N channel MOS transistors 81n1 and 81n6 increase and their
drain currents Ic also increase. Accordingly, the drain currents Ic
of the P channel MOS transistors 81p1 and 81p2 also increase and
the drain current Ic of the P channel MOS transistor 81p2 increases
than the drain current NL*Ilim of the N channel MOS transistor
81n3. As a result, the current Ic-NL*Ilim corresponding to the
difference between the drain current Ic of the P channel MOS 81p2
and the drain current NL*Ilim of the N channel MOS transistor 81n3
flows into the N channel MOS transistors 81n4 and 81n5.
[0252] The control current Ip that flows through the diode-coupled
P channel MOS transistor 81p5 is set by the difference current
(NG-1)*Ic-NL*Ilim between the drain current of NG*(Ic-NL*Ilim) from
the P channel MOS transistor 81p4 of the P channel MOS transistors
81p3 and 81p4 in which the current mirror ratio is set to 1:NG, and
the drain current Ic of the N channel MOS transistor 81n6.
[0253] The value NG of the current mirror ratio 1:NG between the P
channel MOS transistors 81p3 and 81p4 of the voltage-current
converter (VIC) 81 shown in FIG. 14 can be adjusted by the
adjustment signal G. As the value of the adjustment signal G
increases, the value of NG also increases and the control current
Ip flowing through the diode-coupled P channel MOS transistor 81p5
also increases. Assuming that the adjustment signal G and the value
NG are equal to each other, the value of the control current Ip
becomes constant with respect to an increase in the control voltage
Vc where the value of NG is 1, without increasing the control
current Ip with the increase in the control voltage Vc. When the
adjustment signal G and the value of NG are 2 or more, the control
current IP increases with the increase in the control voltage
Vc.
[0254] The value NL of the current mirror ratio 1:NL between the N
channel MOS transistors 81n2 and 81n3 of the voltage-current
converter (VIC) 81 shown in FIG. 14 can be set by the adjustment
signal L. Assuming that the adjustment signal L and the value NL
are equal to each other, the value of NL also increases as the
value of the adjustment signal L increases, and hence the value of
the drain current NL*Ilim of the N channel MOS transistor 81n3 also
increases. After doing so, the level of the control current Ip
flowing through the diode-coupled P channel MOS transistor 81p5,
which has been determined by the difference current
(NG-1)*Ic-NL*Ilim, is also reduced with the increases in the value
of the adjustment signal L and the value of NL.
[0255] FIG. 15 is a diagram for describing a calibration operation
of the PLL according to the third embodiment of the present
invention shown in FIGS. 12 through 14.
[0256] When the calibration operation of the PLL shown in FIG. 15
is started, the selection signal S becomes S="1" at Step 150.
Therefore, the selector (SEL) 7 of the PLL shown in FIG. 12 selects
an input first reference voltage V.sub.REF1 as an output control
voltage Vc. Since, at this time, a phase frequency detector (PFD) 1
and a charge pump (CP) 2 are respectively controlled to a standby
state by a control signal R high in level, the PLL is controlled to
an open loop. At this time, the adjustment signal T and the
adjustment signal L are respectively set to T="0" and L=maximum
value "MAX", and the values of the adjustment signal G and the
value NG are set to "1". In this initial state, the calibration
adjustment unit (LOGIC) 9 starts counting a divided signal of an
output signal (Fvco) of the voltage controlled oscillator (VCO) 8
by a divider (DIV) 6 at Step 151.
[0257] The calibration adjustment unit (LOGIC) 9 compares a count
result N1 of the output signal (Fvco) with a target value A at Step
152. Incidentally, the target value A corresponds to a lowest
oscillation frequency corresponding to one target frequency
characteristic of the voltage controlled oscillator (VCO) 8. When
the calibration adjustment unit (LOGIC) 9 determines that N1 and A
are expressed in a relationship of N1<A, it is determined at
Step 153 whether the adjustment signal T is of the maximum value
"MAX". When it is determined at Step 153 that the adjustment signal
T is not brought to the maximum value "MAX", the calibration
adjustment unit (LOGIC) 9 updates the adjustment signal T to T=T+1
at Step 154. When it is determined at Step 153 that the adjustment
signal T corresponds to the maximum value MAX, it is determined at
Step 155 whether the adjustment signal L corresponds to the minimum
value "MINI". When it is determined at Step 155 that the adjustment
signal L does not assume the minimum value "MINI", the calibration
adjustment unit (LOGIC) 9 updates the adjustment signal L to L=L-1
at Step 156 and updates the adjustment signal T to an initial value
"0". When it is determined at Step 155 that the adjustment signal L
assumes the minimum value "MINI", an error state is displayed at
Step 157 and the calibration operation is completed.
[0258] The frequency of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 increases in response to the control
voltage Vc corresponding to the first reference voltage V.sub.REF1
selected by the selector (SEL) 7 and the updated adjustment signals
T and L. There is a possibility that an increase in the frequency
of the output signal (Fvco) will be insufficient at first and the
determination as to the relationship of N1<A will continue at
Step 152. There is a possibility that the determination at Step 153
that the adjustment signal T does not assume the maximum value MAX,
the updating of the adjustment signal T at Step 154 and the
adjustment signal L at Step 156 will continue. However, the
increase in the frequency of the output signal (Fvco) becomes
sufficient gradually and the relationship of N1>A is determined
at Step 153.
[0259] FIG. 16 is a diagram showing the manner in which the
oscillation frequency of an output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 increases in response to the updating
of an adjustment signal T and an adjustment signal L and the
updating of an adjustment signal T and an adjustment signal L in
the calibration operation of the PLL according to the third
embodiment of the present invention shown in FIGS. 12 through
15.
[0260] Since a relationship of N1>A targeted when the adjustment
signal L is "1" and the adjustment signal T is "0" is first
determined in the example of FIG. 16, the final updated value of
the adjustment signal L is set to "1" and the final updated value
of the adjustment signal T is set to "0". Namely, at Step 158, the
calibration adjustment unit (LOGIC) 9 sets the adjustment signal L
to the final updated value "1" (L=LN1>A hold) and sets the
adjustment signal T to the final updated value "0" (T=TN1>A
hold).
[0261] In this condition, the calibration adjustment unit (LOGIC) 9
starts counting a divided signal of the output signal (Fvco) of the
voltage controlled oscillator (VCO) 8 by the divider (DIV) 6 at
Step 159 and stores a count result N2 in a built-in memory of the
semiconductor integrated circuit.
[0262] Next, the calibration adjustment unit (LOGIC) 9 changes the
selection signal S from S="1" to S="2" at Step 1510. In doing so,
the selector (SEL) 7 of the PLL shown in FIG. 12 switches the input
first reference voltage V.sub.REF1 to a second reference voltage
V.sub.REF2 slightly higher in level than it as the output control
voltage Vc in response to the change of the selection signal S from
S="1" to S="2". The frequency of the output signal (Fvco) of the
voltage controlled oscillator (VCO) 8 slightly increases in
response to the change of the control voltage Vc supplied to the
voltage controlled oscillator (VCO) 8 from the first reference
voltage V.sub.REF1 to the second reference voltage V.sub.REF2. In
this state, the calibration adjustment unit (LOGIC) 9 starts
counting a divided signal of the output signal (Fvco) of the
voltage controlled oscillator (VCO) 8 by the divider (DIV) 6 at
Step 1510 and stores a count result N3 in the built-in memory of
the semiconductor integrated circuit.
[0263] Next, at Step 1511, the calibration adjustment unit (LOGIC)
9 compares the count result N3 of the output signal (Fvco) with a
target value B and further compares a difference N3-N2 between the
count result N3 and the count result N2 with a target value C.
Incidentally, the target value B and the target value C
respectively correspond to a VCO oscillation frequency and AC
frequency control sensitivity each corresponding to a target
frequency characteristic of the voltage controlled oscillator (VCO)
8. The VCO oscillation frequency indicates the oscillation
frequency of the voltage controlled oscillator (VCO) 8 where the
control voltage Vc is set to a predetermined value, whereas the AC
frequency control sensitivity indicates control sensitivity of a
width of change in the oscillation frequency of the voltage
controlled oscillator (VCO) 8 when the control voltage Vc changes
in a predetermined range. When the calibration adjustment unit
(LOGIC) 9 determines at Step 1511 that the count result and the
target value are expressed in a relationship of N3<B or a
relationship of N3-N2<C, the calibration adjustment unit (LOGIC)
9 updates the adjustment signal G to G=G+1 at Step 1512.
[0264] The frequency of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 increases in response to the increase
and updating of the adjustment signal G. There is a possibility
that an increase in the frequency will be insufficient at first and
the determination as to the relationship of N3<B or the
relationship of N3-N2<C at Step 1511 will continue. There is a
possibility that the updating of the adjustment signal G at Step
1512 will continue. However, the increase in the frequency becomes
sufficient gradually and the relationship of N3>B and the
relationship of N3-N2>C are determined at Step 1511.
[0265] FIG. 17 is a diagram showing the manner in which the
frequency of an output signal (Fvco) of the voltage controlled
oscillator (VCO) 8 increases in response to the updating of an
adjustment signal G in the calibration operation of the PLL
according to the third embodiment of the present invention shown in
FIGS. 12 through 16.
[0266] Since a relationship of N3>B and a relationship of
N3-N2>C targeted when the updated value of the adjustment signal
G is "2" are first determined in the example of FIG. 17, the final
updated value of the adjustment signal G is set to "2". Namely, at
Step 1513, the calibration adjustment unit (LOGIC) 9 sets the
adjustment signal G to the final updated value "2" (G=G@N3>B and
N3-N2>C hold) and restores the selection signal S from S="2" to
S="0". Since, at this time, the calibration adjustment unit (LOGIC)
9 restores the control signal R from a high level to a low level,
the phase frequency detector (PFD) 1 and the charge pump (CP) 2 are
controlled to an active state in response to the control signal R
low in level. Therefore, the PLL is controlled to a closed loop. In
response to the selection signal S="0", the selector (SEL) 7
switches the input second reference voltage V.sub.REF1 to the
output signal of the loop filter (LP) 3 as the output's control
voltage Vc. Thus, the PLL is brought to the normal operating period
corresponding to the closed loop, so that the phase and frequency
of the output signal of the divider (DIV) 6 responsive to the
output signal of the voltage controlled oscillator (VCO) 8 of the
PLL respectively coincide with the phase and frequency of the
corresponding reference signal Fref, thereby enabling a lock
operation of the PLL.
[0267] Thus, the calibration of the adjustment signal T, adjustment
signal L and adjustment signal G of the voltage controlled
oscillator (VCO) 8 in the PLL shown in FIG. 12 can be executed by
the calibration operation shown in FIG. 15. Incidentally, the value
of the first reference voltage V.sub.REF1 and the value of the
second reference voltage V.sub.REF2 are set extremely close to the
value of the control voltage Vc supplied from the loop filter (LP)
3 to the voltage controlled oscillator for the PLL lock operation
during the normal operating period of the PLL. Namely, the
frequency fvco of the output signal (Fvco) of the voltage
controlled oscillator (VCO) 8 during the normal operating period of
the PLL according to the third embodiment of the present invention
shown in FIG. 12 is given in a relational expression of fvco=N*fref
assuming that the division ratio of the divider (DIV) 6 is N and
the frequency of the reference signal Fref is fref. Thus, the first
reference voltage V.sub.REF1 and the second reference voltage
V.sub.REF2 each set extremely close to the value of such a control
voltage Vc as to obtain the oscillation output signal (Fvco) having
the frequency fvco given in this relational expression, are
supplied to the voltage controlled oscillator 8 during the period
of the calibration operation.
[0268] Even during the calibration operation of the PLL according
to the third embodiment of the present invention, the relationship
of N3-N2>C is maintained between the first reference voltage
V.sub.REF1 and the second reference voltage V.sub.REF2. It is
possible to compensate for the value of the AC frequency control
sensitivity Kv=C/(V.sub.REF2=V.sub.REF1) between the first
reference voltage V.sub.REF1 and the second reference voltage
V.sub.REF2.
[0269] FIG. 18 is a diagram showing another configuration of the
voltage-current converter (VIC) 81 included in the voltage
controlled oscillator (VCO) 8 shown in FIG. 13.
[0270] Namely, the voltage-current converter (VIC) 81 shown in FIG.
18 comprises four P channel MOS transistors 81p1 through 81p4 and
seven N channel MOS transistors 81n1 through 81n7. A control
voltage Vc is supplied to its corresponding gate of the N channel
MOS transistor 81n1. The gain and drain currents Ic of the N
channel MOS transistor 81n1 can be adjusted by an adjustment signal
T.
[0271] The N channel MOS transistor 81n2 diode-coupled by coupling
its gate and drain is supplied with a reference current Ilim whose
current value is set by a resistor R, from a reference voltage
V.sub.LIM. A gate of the N channel MOS transistor 81n3 is coupled
to its corresponding gate and drain of the N channel MOS transistor
81n2 so as to configure a current mirror along with the
diode-coupled N channel MOS transistor 81n2. The gain and drain
current of the N channel MOS transistor 81n3 can be adjusted by an
adjustment signal L. A drain of the N channel MOS transistor 81n3
is supplied with the drain current Ic of the N channel MOS
transistor 81n1 via the two P channel MOS transistors 81p1 and 81p2
that configure a current mirror. Further, a current mirror
configured by the two N channel MOS transistors 81n4 and 81n5 is
coupled to the drain of the N channel MOS transistor 81n3. A gain
and drain current of the N channel MOS transistor 81n5 can be
adjusted by an adjustment signal G.
[0272] A drain of the N channel MOS transistor 81n5 is supplied
with the drain current Ic of the N channel MOS transistor 81n1 via
the two P channel MOS transistors 81p1 and 81p3 that configure a
current mirror. Further, a current mirror configured by the tow N
channel MOS transistors 81n6 and 81n7 is coupled to the drain of
the N channel MOS transistor 81n5. The P channel MOS transistor
81p4 diode-coupled by its gate-drain coupling is coupled between a
drain of the N channel MOS transistor 81n7 and a source voltage
V.sub.DD.
[0273] A control current Ip that flows through the P channel MOS
transistor 81p4 diode-coupled to the diode-coupled N channel MOS
transistor 81n6 becomes a current corresponding to the difference
between a drain current of the P channel MOS transistor 81p3 and
the drain current of the N channel MOS transistor 81n5. The
difference current is converted to its corresponding output voltage
Vp by the diode-coupled P channel MOS transistor 81p4. The output
voltage Vp is supplied to the delays 521, 522 and 523 of the
current controlled oscillator (CCO) 52 of the voltage controlled
oscillator (VCO) 8 shown in FIG. 13 as a bias voltage, so that
respective operating currents and delay times of the delays 521,
522 and 523 are set. Therefore, the oscillation frequency of the
voltage controlled oscillator (VCO) 8 is determined.
[0274] The operation of the voltage-current converter (VIC) 81
shown in FIG. 18 will next be described.
[0275] The drain current Ic of the N channel MOS transistor 81n1
whose gate is supplied with the control voltage Vc is supplied to
the drain of the N channel MOS transistor 81n3 via a current mirror
having a current mirror ratio of 1:1, which has been configured by
the two P channel MOS transistors 81p1 and 81p2. On the other hand,
since the current mirror ratio between the N channel MOS
transistors 81n2 and 81n3 is set to 1:NL, the drain current of the
N channel MOS transistor 81n3 becomes NL*Ilim. Thus, the current
Ic-NL*Ilim corresponding to the difference between the drain
current Ic of the P channel MOS transistor 81p2 and the drain
current NL*Ilim of the N channel MOS transistor 81n3 flows into the
diode-coupled N channel MOS transistor 81n4.
[0276] Since the current mirror ratio between the N channel MOS
transistors 81n4 and 81n5 is set to 1: NG, the drain current of the
N channel MOS transistor 81n5 is brought to NG(Ic-NL*Ilim).
[0277] On the other hand, since the drain current Ic is flowing
through the P channel MOS transistor 81p3, the value of the
difference current flowing into the diode-coupled N channel MOS
transistor 81n4 becomes (1-NG)*Ic+NL*Ilim. Thus, the value of the
difference current becomes the control current Ip that flows
through the diode-coupled P channel MOS transistor 81p4.
[0278] The calibration operation of the PLL according to the third
embodiment of the present invention shown in FIG. 15 is modified in
the following manner corresponding to the voltage-current converter
(VIC) 81 shown in FIG. 18.
[0279] At Step 150, the adjustment signal T and the adjustment
signal L are respectively set to T="0" and L="0", and the
adjustment signal G and the value of the value NG are respectively
set to "0". It is determined at Step 155 whether the adjustment
signal L is of the minimum value "MINI". The adjustment signal L is
updated to L=L -1 at Step 156, and the adjustment signal G is
updated to G=G -1 at Step 1512. Incidentally, the gain and drain
current of the N channel MOS transistor 81n5 in the current mirror
type N channel MOS transistors 81n4 and 81n5 decrease with an
increase in the value of the adjustment signal G, the value NG
becomes a negative value. Since the gain and drain current of the N
channel MOS transistor 81n3 in the current mirror type transistors
81n2 and 81n3 decrease with an increase in the value of the
adjustment signal L, the value NL also becomes a negative
value.
Fourth Embodiment
[0280] FIG. 21 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a fourth
embodiment of the present invention.
[0281] The PLL shown in FIG. 21 differs from the PLL according to
the first embodiment of the present invention shown in FIG. 1 in
that the calibration adjustment unit 9 included in the PLL of FIG.
1 is replaced with a register (Reg) 10 in the PLL shown in FIG.
21.
[0282] Even at the PLL shown in FIG. 21 in a manner similar to the
PLL according to the first embodiment of the present invention
described in FIGS. 1 through 7, FIG. 19 and FIGS. 32 and 33, the
frequency characteristic of a voltage controlled oscillator (VCO) 8
is adjusted so as to assume a desired characteristic by its
calibration operation.
[0283] Although not shown in the semiconductor integrated circuit
shown in FIG. 21, a central processing unit (CPU) for executing the
same calibration operation as that according to the first
embodiment of the present invention is included therein. The
central processing unit (CPU) supplies a frequency control
sensitivity adjustment signal T, an offset frequency adjustment
signal O, a selection signal S and a control signal R from the
register (Reg) 10 to the PLL in such a manner that the frequency
characteristic of the voltage controlled oscillator (VCO) 8
included in the PLL of FIG. 21 assumes the desired characteristic.
Thus, the register (Reg) 10 comprises a plurality of control
registers which store therein respective control data about the
frequency control sensitivity adjustment signal T, offset frequency
adjustment signal O, selection signal S and control signal R. The
central processing unit (CPU) updates the control data of the
register (Reg) 10 in accordance with control steps for the same
calibration operation as that for the first embodiment.
Fifth Embodiment
[0284] FIG. 22 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a fifth
embodiment of the present invention.
[0285] The PLL shown in FIG. 22 differs from the PLL according to
the second embodiment of the present invention shown in FIG. 8 in
that the calibration adjustment unit 9 included in the PLL of FIG.
8 is replaced with a register (Reg) 10 in the PLL shown in FIG.
22.
[0286] Even at the PLL shown in FIG. 22 in a manner similar to the
PLL according to the second embodiment of the present invention
described in FIGS. 8 through 11, the frequency characteristic of a
voltage controlled oscillator (VCO) 8 is adjusted so as to assume a
desired characteristic by a calibration operation.
[0287] Although not illustrated in the semiconductor integrated
circuit shown in FIG. 22, a central processing unit (CPU) for
executing the same calibration operation as that according to the
first embodiment of the present invention is included therein. The
central processing unit (CPU) supplies a frequency control
sensitivity adjustment signal T, an offset frequency adjustment
signal O, a selection signal S and a control signal R from the
register (Reg) 10 to the PLL in such a manner that the frequency
characteristic of the voltage controlled oscillator (VCO) 8
included in the PLL of FIG. 22 assumes the desired characteristic.
Thus, the register (Reg) 10 comprises a plurality of control
registers which store therein respective control data about the
frequency control sensitivity adjustment signal T, offset frequency
adjustment signal O, selection signal S and control signal R. The
central processing unit (CPU) updates the control data of the
register (Reg) 10 in accordance with control steps for the same
calibration operation as that for the first embodiment.
Sixth Embodiment
[0288] FIG. 23 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a sixth
embodiment of the present invention.
[0289] The PLL shown in FIG. 23 differs from the PLL according to
the third embodiment of the present invention shown in FIG. 12 in
that the calibration adjustment unit 9 included in the PLL of FIG.
12 is replaced with a register (Reg) 10 in the PLL shown in FIG.
23.
[0290] Even at the PLL shown in FIG. 23 in a manner similar to the
PLL according to the third embodiment of the present embodiment
described in FIGS. 12 through 18, the frequency characteristic of a
voltage controlled oscillator (VCO) 8 is adjusted so as to assume a
desired characteristic by a calibration operation.
[0291] Although not illustrated in the semiconductor integrated
circuit shown in FIG. 23, a central processing unit (CPU) for
executing the same calibration operation as that according to the
first embodiment of the present invention is included therein. The
central processing unit (CPU) supplies an adjustment signal T, an
adjustment signal L, an adjustment signal G, a selection signal S
and a control signal R from the register (Reg) 10 to the PLL in
such a manner that the frequency characteristic of the voltage
controlled oscillator (VCO) 8 included in the PLL of FIG. 23
assumes the desired characteristic. Thus, the register (Reg) 10
comprises a plurality of control registers which store therein
respective control data about the adjustment signal T, adjustment
signal L, adjustment signal G, selection signal S and control
signal R. The central processing unit (CPU) updates the control
data of the register (Reg) 10 in accordance with control steps for
the same calibration operation as that for the first
embodiment.
Seventh Embodiment
[0292] FIG. 31 is a diagram showing a configuration of a PLL built
in a semiconductor integrated circuit according to a seventh
embodiment of the present invention.
[0293] The PLL shown in FIG. 31 differs from the PLL according to
the first embodiment of the present invention shown in FIG. 1 in
that the charge pump (CP) 2 included in the PLL of FIG. 1 is
replaced with a first charge pump (CPM) 2a and a second charge pump
(CPS) 2b. A loop filter (LP) 3 of the PLL shown in FIG. 31
comprises a resistor R1 and a capacitor C1 for determining a zero
point frequency f1. A frequency f2 is mainly determined by the
resistor R1, capacitor C1 and capacitor C2. Incidentally, the loop
filter (LP) 3 includes a low pass filter comprised of a resistor R2
and a capacitor C3.
[0294] In the PLL shown in FIG. 31, an up output signal UP of a
phase frequency detector (PFD) 1 is supplied to a charge control
input terminal of the first charge pump (CPM) 2a and a discharge
control input terminal of the second charge pump (CPS) 2b. A down
output signal DN of the phase frequency detector (PFD) 1 is
supplied to a discharge control input terminal of the first charge
pump (CPM) 2a and a charge control input terminal of the second
charge pump (CPS) 2b. Accordingly, the first charge pump (CPM) 2a
and the second charge pump (CPS) 2b are driven in antiphase to each
other in response to the up output signal UP and the down output
signal DN of the phase frequency detector (PFD) 1.
[0295] Further, a ratio .beta. (i2/i1) between a charge/discharge
current i1 of the first charge pump (CPM) 2a and a charge/discharge
current i2 of the second charge pump (CPS) 2b is set to a
predetermined value such as 0.9 or the like. When the zero point
frequency f1 is set by the resistor R1 and capacitor C1 of the loop
filter (LP) 3, the zero point frequency f1 is set by a relational
expression for dividing a time constant C1R1 by the ratio
.beta..
[0296] Thus, since the capacitor C1 small in capacitance value can
be used when the zero point frequency f1 of the same value is set,
the loop filter (LP) 3 can easily be built in a semiconductor chip
of the semiconductor integrated circuit. Incidentally, since the
PLL which includes the first and second charge pumps and makes it
easy to build the loop filter in the semiconductor integrated
circuit, has been described in Japanese Unexamined Patent
Publication No. 2005-184771, refer to it.
[0297] The first charge pump (CPM) 2a and the second charge pump
(CPS) 2b of the PLL shown in FIG. 31 respectively have such
characteristics as shown in FIG. 30 as described at the
commencement of the specification. Thus, the jitter characteristic
of a voltage controlled oscillator (VCO) in the PLL shown in FIG.
31 must be taken into consideration in terms of an increase in the
frequency control sensitivity Kv due to the miniaturized CMOS
manufacturing process shown in FIG. 28 and an increase in the
frequency control sensitivity Kv at the characteristic of the
charge pump 2, which has been shown approximately in the central
part of FIG. 30.
[0298] Thus, even at the PLL shown in FIG. 31, the frequency
characteristic of the voltage controlled oscillator (VCO) 8 is
adjusted to assume a desired characteristic by a calibration
operation in a manner similar to the PLL according to the first
embodiment of the present invention described in FIGS. 1 through 7,
FIG. 19 and FIGS. 32 and 33.
[0299] Further, the PLL shown in FIG. 31 operates as a fractional
PLL by using, as a divider 6, a .SIGMA..DELTA. modulator in which
an average division ratio assumes a value equal to or less than a
decimal fraction by regularly changing the division ratio to a
division ratio N and a different division ratio N+1. In the
fractional PLL, the noise spectrum of the PLL increases since
quantization noise of the .SIGMA..DELTA. modulator used as the
divider 6 passes through a PLL's band.
[0300] Even when the PLL shown in FIG. 31 is configured as the
fractional PLL in this way, the frequency control sensitivity Kv of
the voltage controlled oscillator (VCO) 8 is adjusted to assume a
desired characteristic by a calibration operation in a manner
similar to the first embodiment of the present invention referred
to above. It is thus possible to reduce degradation in the noise
spectrum of the fractional PLL due to the quantization noise of the
.SIGMA..DELTA. modulator used as the divider 6.
Eighth Embodiment
[0301] FIG. 24 is a diagram showing a configuration of an optical
disk apparatus equipped with a semiconductor integrated circuit
according to an eighth embodiment of the present invention.
[0302] The semiconductor integrated circuit 241 according to the
eighth embodiment shown in FIG. 24 has the PLL built therein
according to each of the first through seventh embodiments of the
present invention. The PLL generates clock signals to be supplied
to internal circuits such as a serial-parallel converter, a
parallel-serial converter, etc. built in the semiconductor
integrated circuit 241.
[0303] As an interface for coupling storage media such as an
optical disk apparatus, hard disk drive, etc. to a host computer
such as a personal computer (PC) or the like, ATA (Advanced
Technology Attachment) corresponding to the standard specification
is generally used. By using the ATA standard, the various storage
media can be coupled to the host computer by the same command and
control software. In the eighth embodiment, an optical disk
recording/reproducing device is adopted as a storage medium and
coupled to the host computer by ATA (ATAPI: Advanced Technology
Attachment Packet Interface).
[0304] The semiconductor integrated circuit 241 mounted to the
optical disk recording/reproducing device according to the eighth
embodiment shown in FIG. 24 comprises an ATA interface (ATAPI) 2411
coupled to the host computer 242.
[0305] A signal processing unit (READWRITE) 2412 of the
semiconductor integrated circuit 241 is coupled to an optical
pickup 244 for applying a light beam onto an optical disk 243 used
as a storage medium of the optical disk recording/reproducing
device to thereby perform reading and writing of data. A reference
voltage generator (BGR) 2413 and a crystal oscillator 245 are
coupled to the signal processing unit 2412.
[0306] Parallel data read from the optical disk 243 is supplied
from the signal processing unit 2412 to a serializer 24114. A
parallel-serial converter lying inside the serializer 24114
supplies read serial data RX synchronized with a clock CLK
generated from a PLL 24115 to the host computer 242.
[0307] On the other hand, write serial data TX sent from the host
computer 242 is supplied to a clock data recovery unit (CDR) 24112.
The clock data recovery unit (CDR) 24112 extracts clock data CLK
and serial data contained in the write serial data TX using a PLL
24113 and supplies the same to a deserializer (DES) 24111. The
deserializer (DES) 24111 supplies write parallel data synchronized
with the supplied clock data CLK to the signal processing unit
2412.
[0308] The PLL according to each of the first through seventh
embodiments of the present invention is adopted for the PLL 24115
for the data reading and the PLL 24113 for the data writing, both
of which have been built in the semiconductor integrated circuit
241 according to the eighth embodiment shown in FIG. 24. It is thus
possible to configure the optical disk apparatus capable of stable
data reading/writing operations from/to the optical disk 243.
Ninth Embodiment
[0309] FIG. 25 is a diagram showing a configuration of an optical
disk apparatus equipped with a semiconductor integrated circuit
according to a ninth embodiment of the present invention.
[0310] A signal processing unit (READWRITE) 2512 of the
semiconductor integrated circuit 251 according to the ninth
embodiment shown in FIG. 25 has the PLL built therein according to
each of the first through seventh embodiments of the present
invention.
[0311] The semiconductor integrated circuit 251 mounted to an
optical disk recording/reproducing device according to the ninth
embodiment shown in FIG. 25 also comprises an ATA interface (ATAPI)
2511 coupled to a host computer 252. The ATA interface (ATAPI) 2511
can adopt the same internal configuration as the ATA interface
(ATAPI) 2411 of the semiconductor integrated circuit 241 according
to the eighth embodiment shown in FIG. 24.
[0312] A signal processing unit (READWRITE) 2512 of the
semiconductor integrated circuit 251 is coupled to an optical
pickup 254 for applying a light beam onto an optical disk 253 used
as a storage medium of the optical disk recording/reproducing
device to thereby perform reading and writing of data. A reference
voltage generator (BGR) 2513 and a crystal oscillator 255 are
coupled to the signal processing unit 2512.
[0313] Data read from the optical pickup 254 is supplied to a read
logic circuit 25123 and a PRML type read signal processing circuit
25124 in the signal processing unit 2512, and hence a clock signal
contained in the data read from the optical pickup 254 is
reproduced by the PLL lying inside the PRML type read signal
processing circuit 25124. Incidentally, PRML is an abbreviation of
Partial Response Mostly Likelihood. The read logic circuit 25123
processes the data read from the optical pickup 254 using the clock
signal reproduced by the PRML type read signal processing circuit
25124 and supplies the processed data to the ATA interface (ATAPI)
2511.
[0314] Write data from the ATA interface (ATAPI) 2511 is supplied
to a write logic circuit 25121 of the signal processing unit 2512.
The write logic circuit 25121 processes the write data from the ATA
interface (ATAPI) 2511 in sync with a clock signal supplied from
the corresponding PLL 25122 and supplies it to the optical pickup
254.
[0315] The PLL according to each of the first through seventh
embodiments of the present invention is adopted for the PLL lying
inside the PRML type read signal processing circuit 25124 built in
the signal processing unit 2512 of the semiconductor integrated
circuit 251 according to the ninth embodiment shown in FIG. 25, and
the PLL 25122 for the data writing. It is thus possible to
configure an optical disk apparatus capable of stable data
reading/writing operations from/to the optical disk 243.
[0316] While the invention made above by the present inventors has
been described specifically on the basis of the preferred
embodiments, the present invention is not limited to the
embodiments. It is needless to say that various changes can be made
thereto within the scope not departing from the gist thereof.
[0317] For example, the selector (SEL) 7 of the PLL according to
the seventh embodiment of the present invention shown in FIG. 31
can be substituted with the form of the selector (SEL) 7 of the PLL
according to the second embodiment of the present invention shown
in FIG. 8. In this case, the frequency characteristic of the
voltage controlled oscillator (VCO) 8 can be adjusted to assume a
desired characteristic by a calibration operation similar to that
for the PLL according to the second embodiment of the present
invention described in FIGS. 8 through 11.
[0318] Further, the selector (SEL) 7 of the PLL according to
seventh embodiment of the present invention shown in FIG. 341 can
be substituted with the form of the selector (SEL) 7 of the PLL
according to the second embodiment of the present invention shown
in FIG. 12. In this case, the frequency characteristic of the
voltage controlled oscillator (VCO) 8 can be adjusted to assume a
desired characteristic by a calibration operation similar to that
for the PLL according to the third embodiment of the present
invention described in FIGS. 12 through 18.
[0319] Furthermore, the control sensitivities of the currents Ic,
Ir, NLIlim and the like based on the adjustment signals T, O, L and
G at the voltage-current converter (VIC) 81 shown in each of FIGS.
3, 14 and 18 were adjusted by their settings by the adjustment
signals of the selectors 8124 and 8125 coupled to the gates of the
MSO transistors 8122 and 8123 as shown in FIG. 4. As described in
the patent document 1 as a method other than the above, however,
the resistance value of the conversion resistor between the source
of the conversion MOS transistor of the voltage-current converter
and the ground potential can also be set by the value of each
adjustment signal.
* * * * *