U.S. patent application number 12/726323 was filed with the patent office on 2011-07-28 for semiconductor integrated circuit device and oscillation frequency calibration method.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Mototsugu HAMADA, Daisuke MIYASHITA, Yuji SATOH.
Application Number | 20110181367 12/726323 |
Document ID | / |
Family ID | 44308527 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110181367 |
Kind Code |
A1 |
SATOH; Yuji ; et
al. |
July 28, 2011 |
SEMICONDUCTOR INTEGRATED CIRCUIT DEVICE AND OSCILLATION FREQUENCY
CALIBRATION METHOD
Abstract
A semiconductor integrated circuit device includes a DCO and a
storing unit that stores a temperature coefficient of an
oscillation frequency and an absolute value of the oscillation
frequency, which should be set in the DCO, corresponding to
potential obtained from a voltage source that changes with a
monotonic characteristic with respect to temperature.
Inventors: |
SATOH; Yuji;
(Nagareyama-shi, JP) ; HAMADA; Mototsugu;
(Yokohama-shi, JP) ; MIYASHITA; Daisuke;
(Kawasaki-shi, JP) |
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
44308527 |
Appl. No.: |
12/726323 |
Filed: |
March 17, 2010 |
Current U.S.
Class: |
331/34 |
Current CPC
Class: |
H03L 1/025 20130101;
H03L 7/099 20130101; H03L 2207/06 20130101; H03L 7/0995 20130101;
H03L 1/026 20130101 |
Class at
Publication: |
331/34 |
International
Class: |
H03L 7/00 20060101
H03L007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 27, 2010 |
JP |
2010-015676 |
Claims
1. A semiconductor integrated circuit device comprising: an
oscillator; and an oscillation-frequency calibrator configured to
transmit a control signal for controlling the oscillator, based on
information for determining an oscillation frequency of the
oscillator and potential information from a voltage source
configured to fluctuate with a monotonic characteristic with
respect to temperature.
2. The semiconductor integrated circuit device of claim 1, wherein
the oscillation-frequency calibrator is configured to generate the
control signal based on the information for determining the
oscillation frequency and the potential information at least two
temperatures.
3. The semiconductor integrated circuit device of claim 1, wherein
the oscillation-frequency calibrator is configured to calculate a
temperature coefficient and an absolute value of a desired
oscillation frequency based on the information for determining the
oscillation frequency and the potential information, and to
generate the control signal.
4. The semiconductor integrated circuit device of claim 3, further
comprising a current source configured to generate a first control
signal corresponding to the temperature coefficient, wherein the
oscillator is an inductance-capacitance (LC) oscillator configured
to operate in response to the first control signal and a second
control signal corresponding to the absolute value.
5. The semiconductor integrated circuit device of claim 3, further
comprising a current source configured to generate the control
signal based on the temperature coefficient and the absolute value,
wherein the oscillator is a ring oscillator configured to operate
in response to the control signal.
6. The semiconductor integrated circuit device of claim 3, wherein
the oscillation-frequency calibrator is configured to generate the
control signal based on: a temperature coefficient representing a
linear interpolant between a temperature coefficient of the
oscillation frequency corresponding to a first potential from the
voltage source and a temperature coefficient of the oscillation
frequency corresponding to a second potential from the voltage
source; and an absolute value representing a linear interpolant
between an absolute value of the oscillation frequency
corresponding to the first potential from the voltage source and an
absolute value of the oscillation frequency corresponding to the
second potential from the voltage source.
7. The semiconductor integrated circuit device of claim 3, wherein
the oscillation-frequency calibrator is configured to linearly
interpolate an Nth order temperature coefficient where N is an
integer equal to or larger than 2 and an absolute value to generate
the control signal.
8. The semiconductor integrated circuit device of claim 3, wherein
the oscillation-frequency calibrator comprises: a controller
configured to control an oscillation frequency from the oscillator
corresponding with a reference oscillation frequency; a table
comprising a potential from the voltage source configured to
fluctuate with the monotonic characteristic associated with
temperature and the oscillation frequency from the oscillator; and
an oscillation-frequency setting module configured to set a
temperature frequency of an oscillation frequency corresponding to
the potential from the voltage source and an absolute value of the
oscillation frequency corresponding to the potential from the
voltage source, by referring to the table.
9. The semiconductor integrated circuit device of claim 8, further
comprising a frequency divider connected between an input terminal
of the controller and an output terminal of the oscillator.
10. The semiconductor integrated circuit device of claim 8, further
comprising a frequency divider connected between an output terminal
of the controller and an input terminal of the oscillator.
11. The semiconductor integrated circuit device of claim 1, wherein
the oscillation-frequency calibrator is configured to calculate
capacitance or an electric current with the oscillation frequency
substantially constant with respect to temperature based on the
information for determining the oscillation frequency and the
potential information, and to generate the control signal.
12. The semiconductor integrated circuit device of claim 11,
further comprising an oscillation-frequency compensating module
comprising a current source configured to generate the first
control signal based on the capacitance, wherein the oscillator is
an LC oscillator configured to operate in response to the first
control signal and a second control signal corresponding to the
absolute value.
13. The semiconductor integrated circuit device of claim 11,
further comprising a current source configured to generate the
control signal based on the capacitance, wherein the oscillator
comprises a ring oscillator configured to operate in response to
the control signal.
14. The semiconductor integrated circuit device of claim 11,
further comprising: an oscillation-frequency compensating module
comprising a table comprising potential from a voltage source
associated with capacitance or an electric current, the potential
being configured to fluctuate with a monotonic characteristic with
respect to temperature, and the oscillation frequency being
substantially constant with respect to temperature and configured
to fluctuate according to the potential at the capacitance or the
electric current, wherein the oscillation-frequency compensating
module is configured to set capacitance or an electric current
corresponding to the potential from the voltage source referring to
the table.
15. An oscillation frequency calibration method for calibrating an
oscillation frequency of an oscillator, comprising: generating a
control signal based on information for determining an oscillation
frequency of the oscillator and potential information from a
voltage source configured to fluctuate with a monotonic
characteristic with respect to temperature; and controlling the
oscillator with the control signal.
16. The oscillation frequency calibration method of claim 15,
further comprising: calculating a temperature coefficient and an
absolute value of the oscillation frequency based on the
information for determining the oscillation frequency and the
potential information, and generating the control signal.
17. The oscillation frequency calibration method of claim 15,
further comprising calculating capacitance at the oscillation
frequency substantially constant with respect to temperature based
on the information for determining the oscillation frequency and
the potential information, and generating the control signal.
18. The frequency oscillation calibration method of claim 15,
further comprising calculating an electric current at the
oscillation frequency substantially constant with respect to
temperature based on the information for determining the
oscillation frequency and the potential information, and generating
the control signal.
19. The frequency oscillation calibration method of claim 15,
further comprising generating the control signal based on
information for determining an oscillation frequency of the
oscillator at first and second temperatures and potential
information from a voltage source configured to fluctuate with a
monotonic characteristic with respect to temperature at the first
and second temperatures, an electric current at the oscillation
frequency substantially constant with respect to temperature.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2010-015676, filed on Jan. 27, 2010; the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a semiconductor integrated
circuit device and an oscillation frequency calibration method.
[0004] 2. Description of the Related Art
[0005] Oscillators are widely used in semiconductor integrated
circuits. Before the oscillators are shipped, it is necessary to
calibrate an error in an oscillator frequency that occurs in a
manufacturing process. Conventionally, a method of calibrating an
oscillation frequency is known. In recent years, oscillators having
a tight tolerance in oscillation frequency with respect to a
temperature change are often required. There is a demand for a
solution that satisfies such a need.
[0006] As an example of the solution, means for measuring a
correspondence relation of an oscillation frequency with respect to
an absolute temperature and determining a calibration value is
known. However, in this calibration work, extremely long converging
time is required when temperature is accurately changed (e.g.,
changed from T1 to T2). Therefore, the calibration work is a cause
of an increase in cost for the calibration. In some case, unless
the calibration is applied to the temperature in an entire
temperature compensation range, the performance of an oscillator at
the time of shipment cannot be guaranteed and a further increase in
calibration cost is caused. Therefore, there is a demand for a
method that can end the calibration work for an oscillation
frequency in a short time.
[0007] The related art represented by Japanese Patent Application
Laid-Open No. 2008-311884 discloses an oscillation frequency
control method that can adjust, when temperature changes, an
oscillation frequency to a predetermined reference frequency with
high responsiveness and keep the oscillation frequency
constant.
[0008] However, the related art represented by Japanese Patent
Application Laid-Open No. 2008-311884 relates to control of an
oscillation frequency with respect to a temperature change after
the shipment of an oscillator and cannot satisfy the need for
reducing time required for the calibration work for the oscillation
frequency.
[0009] It is an object of the present invention to provide a
semiconductor integrated circuit device and the oscillation
frequency calibration method that can reduce the time required for
the calibration work for the oscillation frequency of the
oscillator.
BRIEF SUMMARY OF THE INVENTION
[0010] A semiconductor integrated circuit device according to an
embodiment of the present invention comprises an oscillator; and an
oscillation-frequency calibrating unit that outputs, based on
information for determining an oscillation frequency of the
oscillator and potential information obtained from a voltage source
that changes with a monotonic characteristic with respect to
temperature, a control signal for controlling the oscillator.
[0011] A oscillation frequency calibration method according to an
embodiment of the present invention comprises generating a control
signal based on information for determining an oscillation
frequency of the oscillator and potential information obtained from
a voltage source that changes with a monotonic characteristic with
respect to temperature; and controlling the oscillator with the
control signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a diagram of a semiconductor integrated circuit
device according to a first embodiment of the present
invention;
[0013] FIG. 2A is a graph of a relation between temperature and an
oscillation frequency;
[0014] FIG. 2B is a graph of a relation between temperature and
voltage reference;
[0015] FIG. 3 is a diagram for explaining operation in calibrating
a DCO;
[0016] FIG. 4 is a diagram for explaining operation after the
shipment of the DCO;
[0017] FIG. 5 is a diagram of a semiconductor integrated circuit
device according to a second embodiment of the present
invention;
[0018] FIG. 6 is a diagram of the internal configuration of a
control unit shown in FIG. 5;
[0019] FIG. 7 is a diagram for explaining control signals after the
shipment of a DCO shown in FIG. 5;
[0020] FIG. 8 is a diagram of a relation between a current source
shown in FIG. 7 and a temperature characteristic;
[0021] FIG. 9A is a diagram of an equivalent circuit of a current
source Is shown in FIG. 8;
[0022] FIG. 9B is a diagram of an equivalent circuit of a current
source 43 shown in FIG. 8;
[0023] FIG. 10 is a diagram of a semiconductor integrated circuit
device according to a third embodiment of the present
invention;
[0024] FIG. 11 is a diagram for explaining a control signal after
the shipment of a DCO shown in FIG. 10;
[0025] FIG. 12 is a diagram of a configuration example in which a
current source is connected to a ring oscillator;
[0026] FIG. 13A is a diagram of an equivalent circuit of a current
source Is shown in FIG. 8;
[0027] FIG. 13B is a diagram of an equivalent circuit of the
current source 43 shown in FIG. 8;
[0028] FIG. 14 is a diagram of a frequency divider connected
between an output end of the DCO and an input end of a control
unit;
[0029] FIG. 15 is a diagram of a frequency divider connected to an
input end of the DCO;
[0030] FIG. 16 is a diagram of a frequency divider connected to an
output end of the control unit;
[0031] FIG. 17 is a graph of data linearly interpolated by an
oscillation-frequency calibrating unit;
[0032] FIG. 18 is a graph for explaining interpolation processing
by a plurality of measurement points;
[0033] FIGS. 19A-19C are graphs of a relation between capacitance
and voltage reference;
[0034] FIG. 20 is a diagram of a look-up table (LUT) according to a
seventh embodiment of the present invention;
[0035] FIG. 21 is a diagram for explaining calibration operation
performed when the seventh embodiment is applied to an LC
oscillator; and
[0036] FIG. 22 is a diagram for explaining a control signal after
the shipment of a DCO.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Exemplary embodiments of a semiconductor integrated circuit
device and an oscillation frequency calibration method according to
the present invention will be explained below in detail with
reference to the accompanying drawings. The present invention is
not limited to the following embodiments.
[0038] FIG. 1 is a diagram of a semiconductor integrated circuit
device according to a first embodiment of the present invention.
FIG. 2A is a graph of a relation between temperature and an
oscillation frequency. FIG. 2B is a graph of a relation between
temperature and voltage reference. FIG. 3 is a diagram for
explaining operation in calibrating a DCO. FIG. 4 is a diagram for
explaining operation after the shipment of the DCO.
[0039] The semiconductor integrated circuit device shown in FIG. 1
includes an oscillation-frequency calibrating unit 40, a voltage
source 20 having a monotonic characteristic with respect to
temperature, an analog to digital converter (ADC) 30, a digital
controlled oscillator (DCO) 50 as a calibration target, and a
control unit 10 that controls the DCO 50.
[0040] An output end of the DCO 50 is connected to an input end of
the control unit 10. A not-shown reference oscillator (which
oscillates at a fixed oscillation frequency irrespectively of
temperature) is connected to the control unit 10. The control unit
10 controls a reference oscillation frequency REF from the
reference oscillator and an output (an oscillation frequency) of
the DCO 50 to coincide with each other and outputs a result of the
control to the DCO 50 as digital information. A stabilized state is
generally represented as a locked state. The DCO 50, the control
unit 10, and the reference oscillation frequency REF form, as a
whole, for example, a delay locked loop (DLL) a phase locked loop
(PLL), or a frequency locked loop (FLL). The output of the control
unit 10 is input to the oscillation-frequency calibrating unit 40
as information (data) for determining an oscillation frequency of
the DCO 50.
[0041] The voltage source 20 is a voltage source having a monotonic
characteristic with respect to temperature. In the voltage source
20, for example, an electric current (proportional to absolute
temperature: Ipat)), which linearly changes with respect to
temperature, is set as a resistance load by a not-shown voltage
reference (band-gap reference: BGR). The ADC 30 converts potential
from the voltage source 20 into a digital signal. Potential
information (addr) converted into the digital signal is input to
the oscillation-frequency calibrating unit 40.
[0042] The oscillation-frequency calibrating unit 40 includes a
look-up table (LUT) 41, an oscillation-frequency setting unit 45,
and a storing unit 42. Information for determining an oscillation
frequency corresponding to the DCO 50 and potential information are
stored in the LUT 41 in advance. The oscillation-frequency setting
unit 45 sets, based on information (data) and potential information
(addr) corresponding to first and second temperatures, a
temperature coefficient of the oscillation frequency and an
absolute value of the oscillation frequency referring to the
information (data) and the potential information (addr) stored in
the LUT 41 in advance. The storing unit 42 stores the set
temperature coefficient and absolute value of the oscillation
frequency.
[0043] A relation among an absolute temperature T (hereafter simply
referred to as "temperature T"), voltage reference V, and an
oscillation frequency F related to calibration of an oscillation
frequency is explained with reference to FIGS. 2A and 2B. The
oscillation frequency F with respect to the temperature T is shown
in FIG. 2A. The oscillation frequency F corresponds to information
for determining an oscillation frequency. The voltage reference V
with respect to the temperature T is shown in FIG. 2B. The voltage
reference V corresponds to potential information from the power
supply source 20. The semiconductor integrated circuit device
according to this embodiment calibrates the DCO 50 using the
voltage reference V having a monotonic characteristic with respect
to temperature and the oscillation frequency F.
[0044] For example, voltage reference and an oscillation frequency
corresponding to temperature T1 are voltage reference V1 and an
oscillation frequency F1. voltage reference and an oscillation
frequency corresponding to the temperature T2 are voltage reference
V2 and an oscillation frequency F2. In other words, the voltage
reference V and the oscillation frequency F are in a one-to-one
correspondence relation with respect to certain temperature. The
semiconductor integrated circuit device according to this
embodiment measures an oscillation frequency of the DCO 50 with
respect to arbitrary temperature and the potential of the voltage
source 20 with respect to the arbitrary temperature and executes,
referring to the LUT 41 in which the oscillation frequency and the
potential of the DCO 50 are stored in advance, calibration for
setting the oscillation frequency to a desired oscillation
frequency.
[0045] A procedure for calibrating the DCO 50 using the information
for determining an oscillation frequency and the potential
information stored in the LUT 41 is specifically explained
below.
[0046] The semiconductor integrated circuit device measures
information (data) and potential information (addr) for determining
an oscillation frequency at appropriate temperature (hereinafter,
"first temperature"). It is assumed that the voltage source 20 and
the DCO 50 are set in environments having substantially the same
temperature changes. Basically, the first temperature can be any
temperature as long as the temperature is within an operation range
of the DCO 50. In a state of the first temperature, the
semiconductor integrated circuit device locks the DCO 50 and inputs
information (data) and potential information (addr) at the first
temperature.
[0047] Subsequently, the semiconductor integrated circuit device
changes the ambient temperature of the voltage source 20 and the
DCO 50 and performs measurement at the temperature after the change
(hereinafter, "second temperature"). The second temperature can be
temperature lower or higher than the first temperature. What is
important is only to change the temperature. Therefore, for
example, the air can be continuously heated by a heater or the like
or a heat source such as a resistor can be set. In a state of the
second temperature, the semiconductor integrated circuit device
locks the DCO 50 and inputs information (data) and potential
information (addr) at the second temperature to the
oscillation-frequency calibrating unit 40.
[0048] As a result, the oscillation-frequency setting unit 45
obtains the information (data) and the potential information (addr)
corresponding to the first and second temperatures. The
oscillation-frequency setting unit 45 sets, based on the
information (data) and the potential information (addr)
corresponding to the first and second temperatures, a temperature
coefficient of the oscillation frequency and an absolute value of
the oscillation frequency referring to the information (data) and
the potential information (addr) stored in the LUT 41 in advance.
The set temperature coefficient and absolute value of the
oscillation frequency are stored in the storing unit 42. After the
shipment of the DCO 50, as shown in FIG. 4, a control signal (data)
derived from the temperature coefficient and the absolute value of
the oscillation frequency stored in the storing unit 42 is output
to the DCO 50. The oscillation frequency of the DCO 50 is
controlled by the control signal.
[0049] As explained above, the semiconductor integrated circuit
device according to this embodiment calibrates the oscillation
frequency of the DCO 50 based on the temperature coefficient and
the absolute value of the oscillation frequency that changes
according to potential obtained from the voltage source 20 that
changes with the monotonic characteristic with respect to
temperature. Therefore, temperature operation involved in the
calibration of the DCO 50 is unnecessary. With the semiconductor
integrated circuit device according to this embodiment, time
required for the calibration work is substantially reduced. As a
result, it is possible to substantially reduce cost for the
calibration of the DCO 50.
[0050] FIG. 5 is a diagram of a semiconductor integrated circuit
device according to a second embodiment of the present invention.
FIG. 6 is an internal diagram of a control unit shown in FIG. 5.
FIG. 7 is a diagram for explaining control signals after the
shipment of a DCO shown in FIG. 5. FIG. 8 is a diagram of a
relation between a current source shown in FIG. 7 and a temperature
characteristic. FIG. 9A is a diagram of an equivalent circuit of a
current source Is shown in FIG. 8. FIG. 9B is a diagram of an
equivalent circuit of a current source 43 shown in FIG. 8. In the
following explanation, components same as those in the first
embodiment are denoted by the same reference numerals and signs and
explanation of the components is omitted. Only differences from the
first embodiment are explained below.
[0051] In the semiconductor integrated circuit device shown in FIG.
5, the DCO 50 according to the first embodiment is realized by an
LC oscillator (a balanced oscillator). Outputs Voutp and Voutn of
the DCO 50 are output to the control unit 10. The control unit 10
shown in FIG. 6 includes a differential single-phase converter 12
and a time-to-digital converter (TDC) 11. The differential
single-phase converter 12 converts the outputs Voutp and Voutn from
the DCO 50 into a single-phase signal. The TDC 11 compares the
single-phase signal from the differential single-phase converter 12
and a reference oscillation frequency REF from the outside and
outputs a difference between the single-phase signal and the
reference oscillation frequency REF as digital information. The
information output from the TDC 11 is input to the
oscillation-frequency calibrating unit 40 as information (data). In
FIG. 5, a voltage source is shown as proportional to absolute
temperature (Vpat). A section shown as On-Chip in FIG. 5 is a
section that is mounted on an oscillator to be shipped.
[0052] A calibration procedure for the DCO 50 is explained below.
The semiconductor integrated circuit device locks the DCO 50 at the
first temperature. The output of the control unit 10 is input to
the oscillation-frequency calibrating unit 40 as information (data)
for determining an oscillation frequency of the DCO 50. The ADC 30
converts Vptat into a digital signal (potential information addr)
and inputs the digital signal to the oscillation-frequency
calibrating unit 40. Subsequently, the semiconductor integrated
circuit device locks the DCO 50 in the state of the second
temperature. The semiconductor integrated circuit device acquires
information (data) and potential information (addr) at the second
temperature. As a result, the oscillation-frequency calibrating
unit 40 obtains the information (data) and the potential
information (addr) corresponding to the first and second
temperatures.
[0053] The oscillation-frequency setting unit 45 sets, based on the
information (data) and the potential information (addr) and the
information (data) and the potential information (addr)
corresponding to the first and second temperatures, a temperature
coefficient and an absolute value of the oscillation frequency
referring to the LUT 41. The set temperature coefficient and
absolute value of the oscillation frequency are stored in the
storing unit 42. After the shipment of the DCO 50, a control signal
derived from the temperature coefficient and the absolute value of
the oscillation frequency stored in the storing unit 42 is output
to the DCO 50. The oscillation frequency of the DCO 50 is
controlled by the control signal.
[0054] The configuration of the oscillation-frequency calibrating
unit 40 is specifically explained below.
[0055] The temperature coefficient and the absolute value of the
oscillation frequency set by the oscillation-frequency setting unit
45 are recorded in the storing unit 42 shown in FIG. 7. The
temperature coefficient of the oscillation frequency is input to
the current source 43. The current source 43 generates a control
signal d1 indicating a control amount of the DCO 50 corresponding
to the temperature coefficient stored in the storing unit 42 and
outputs the control signal d1 to a variable capacitor 51 of the DCO
50. A switch 52 of the DCO 50 is controlled by using the absolute
value of the oscillation frequency as a control signal d2
indicating a control amount of the DCO 50 corresponding to the
absolute value.
[0056] A concept in performing second-order temperature correction
in the current source 43 shown in FIG. 7 is shown in FIG. 8. For
example, a current source having a second-order temperature
characteristic can be realized by adding up a current source Ic
having a zero-th order temperature coefficient, a current source Ip
having a first-order temperature coefficient, and a current source
Is having a second-order temperature coefficient. The current
source Is shown in FIG. 9A can be realized by using the
second-order characteristic of a transistor. The current source 43
shown in FIG. 9B can be realized by using the current sources Ic,
Ip, and Is as shown in FIG. 8. As a result, in addition to an
effect same as that in the first embodiment, it is possible to
calibrate an oscillation frequency taking into account a nonlinear
characteristic of a transistor included in the LC oscillator.
Coefficients Ic, Ip, Is, .alpha., .beta., and .gamma. can be
positive or negative.
[0057] FIG. 10 is a diagram of the configuration of a semiconductor
integrated circuit device according to a third embodiment of the
present invention. FIG. 11 is a diagram for explaining a control
signal after the shipment of a DCO shown in FIG. 10. FIG. 12 is a
diagram of a configuration example in which a current source is
connected to a ring oscillator. FIG. 13A is a diagram of an
equivalent circuit of the current source Is shown in FIG. 8. FIG.
13B is a diagram of an equivalent circuit of the current source 43
shown in FIG. 8. In the following explanation, components same as
those in the first embodiment are denoted by the same reference
numerals and signs and explanation of the components is omitted.
Only differences from the first embodiment are explained below.
[0058] In the semiconductor integrated circuit device shown in FIG.
10, the DCO 50 according to the first embodiment is realized by a
ring oscillator. An output Vout of the DCO 50 is output to a
control unit 13.
[0059] The control unit 13 shown in FIG. 10 has a function
equivalent to that of the TDC shown in FIG. 6. The control unit 13
compares the output Vout from the DCO 50 and the reference
oscillation frequency REF and outputs a difference between the
output Vout and the reference oscillation frequency REF as digital
information. The information output from the control unit 13 is
input to the oscillation-frequency calibrating unit 40 as
information (data). A section shown as On-Chip in FIG. 10 is a
section that is mounted on an oscillator to be shipped. As the ring
oscillator, an example of a single-phase ring oscillator is shown.
However, the ring oscillator can be a differential ring oscillator.
In the case of the differential ring oscillator, the control unit
13 has a configuration equivalent to that of the control unit 10
shown in FIG. 10.
[0060] A calibration procedure for the DCO 50 is explained below.
The semiconductor integrated circuit device locks the DCO 50 at the
first temperature. The output of the control unit 13 is input to
the oscillation-frequency calibrating unit 40 as information (data)
for determining an oscillation frequency of the DCO 50. The ADC 30
converts Vptat into a digital signal. The potential information
(addr) from the ADC 30 converted into the digital signal is input
to the oscillation-frequency calibrating unit 40. Subsequently, the
semiconductor integrated circuit device locks the DCO 50 in the
state of the second temperature and acquires information (data) and
potential information (addr) at the second temperature. As a
result, the oscillation-frequency calibrating unit 40 obtains the
information (data) and the potential information (addr)
corresponding to the first and second temperatures.
[0061] The oscillation-frequency setting unit 45 sets, based on the
information (data) and the potential information (addr) stored in
the LUT 41 in advance and the information (data) and the potential
information (addr) corresponding to the first and second
temperatures, a temperature coefficient and an absolute value of
the oscillation frequency. The set temperature coefficient and
absolute value of the oscillation frequency are stored in the
storing unit 42. After the shipment of the DCO 5, a control signal
(data) derived from the temperature coefficient and the absolute
value stored in the storing unit 42 is output to the DCO 50.
[0062] The configuration of the oscillation-frequency calibrating
unit 40 is specifically explained below.
[0063] In FIG. 11, the temperature coefficient and the absolute
value of the oscillation frequency set by the oscillation-frequency
setting unit 45 are recorded in the storing unit 42. The
temperature coefficient and the absolute value of the oscillation
frequency are input to the current source 43. The current source 43
generates a control signal d3 indicating a control amount of the
DCO 50 corresponding to the temperature coefficient and the
absolute value from the storing unit 42 and outputs the control
signal d3 to transistors 53 and 54 of the DCO 50. As shown in FIG.
12, the current source 43 can be directly connected to the ring
oscillator without the intervention of the transistors 53 and
54.
[0064] The current source Is shown in FIG. 13A can be realized by
using the second-order characteristic of a transistor. As shown in
FIG. 8, the current source 43 shown in FIG. 13B can be realized by
using the current sources Ic, Ip, and Is. As a result, as in the
second embodiment, it is possible to perform highly-accurate
calibration of an oscillation frequency taking into account a
nonlinear characteristic of a transistor included in the ring
oscillator. Coefficients Ic, Ip, Is, .alpha., .beta., and .gamma.
can be positive or negative.
[0065] A semiconductor integrated circuit device according to a
fourth embodiment of the present invention has a configuration
substantially the same as that in the first embodiment. However,
the semiconductor integrated circuit device according to the fourth
embodiment is different in that the semiconductor integrated
circuit device includes a frequency divider 80, 81, or 82. FIG. 14
is a diagram of a frequency divider connected between an output
terminal of the DCO and an input terminal of the control unit. FIG.
15 is a diagram of a frequency divider connected to an input
terminal of the DCO. FIG. 16 is a diagram of a frequency divider
connected to an output terminal of the control unit. In the
following explanation, components same as those in the first
embodiment are denoted by the same reference numerals and signs and
explanation of the components is omitted. Only differences from the
first embodiment are explained below.
[0066] The frequency divider 80 shown in FIG. 14 is connected
between an output terminal of the DCO 50 and an input terminal of
the control unit 10 (or a control unit 18). The frequency divider
80 divides an oscillation frequency of the DCO 50 and outputs the
divided oscillation frequency to the control unit 10. By adopting
this configuration, it is possible to narrow a frequency operation
range of a digital converter (equivalent to, for example the TDC)
or the like included in the control unit 10. The frequency divider
81 shown in FIG. 15 is connected to an input terminal of the DCO 50
and divides a signal input to the DCO 50. The frequency divider 82
shown in FIG. 16 is connected to an output end of the control unit
10, divides a signal from the control unit 10, and outputs
information for determining a divided oscillation frequency to the
DCO 50 and the oscillation-frequency calibrating unit 40.
Configurations shown in FIGS. 15 and 16 have a function equivalent
to that of the configuration shown in FIG. 14 and can obtain an
effect equivalent to that of the configuration shown in FIG. 14.
The frequency divider 80, 81, or 82 can be set in the inside of the
control unit 10.
[0067] In the first to fourth embodiments, the voltage references
V1 and V2 and the oscillation frequencies F1 and F2 with respect to
the two temperatures T1 and T2 are measured. In a fifth embodiment
of the present invention, voltage reference and an oscillation
frequency between these two points are calculated by linear
approximation.
[0068] FIG. 17 is a diagram of data linearly interpolated by the
oscillation-frequency calibrating unit. The oscillation-frequency
setting unit 45 linearly interpolates the measured oscillation
frequencies F1 and F2 and the measured voltage references V1 and
V2. The oscillation-frequency setting unit 45 calculates a
temperature coefficient with respect to the current source 43 based
on an oscillation frequency and voltage reference after the linear
interpolation. As a result, it is possible to accurately perform
calibration of the DCO 50.
[0069] In a sixth embodiment of the present invention, the voltage
reference T and the oscillation frequency F with respect to three
or more temperatures are measured and a high-order temperature
coefficient such as a quadratic function is calculated.
[0070] FIG. 18 is a graph for explaining interpolation by a
plurality of measurement points. The oscillation-frequency setting
unit 45 performs interpolation processing for a plurality of
oscillation frequencies F1 to Fn and a plurality of voltage
references V1 to Vn measured at a plurality of temperatures T1 to
Tn. Because a high-order temperature coefficient can be obtained by
interpolating the oscillation frequencies and the voltage
references using the temperatures T1 to Tn, it is possible to
calibrate the DCO 50 at higher accuracy compared with the fifth
embodiment.
[0071] FIGS. 19A-19C are diagrams of a relation between capacitance
and voltage reference in a seventh embodiment of the present
invention. In FIG. 19A, a fixed oscillation frequency F0 and a
temperature characteristic of an oscillation frequency of the DCO
50 set to a predetermined capacitance C are shown with respect to
temperature. In FIG. 19A, as an example, temperature
characteristics with respect to five kinds of capacitances are
shown. In FIG. 19B, a plurality of capacitances at which the
frequency F is the fixed oscillation frequency F0 with respect to
temperature are shown. For example, capacitances at which the
oscillation frequency F is F0 at the temperatures T1 to T3 are C1
to C3. In FIG. 19C, the voltage reference V corresponding to
temperature is shown. In FIGS. 19B and 19C, because the temperature
is common, the voltage reference V and the capacitance C are in a
one-to-one relation with respect to a change in the
temperature.
[0072] FIG. 20 is a diagram of a LUT according to the seventh
embodiment. In the LUT 41, the capacitance C (data), which is
measured instead of the oscillation frequency F, indicating a
control amount at which the oscillation frequency F is F0 is
stored.
[0073] FIG. 21 is a diagram for explaining calibration operation
performed when the seventh embodiment is applied to an LC
oscillator. As in the first embodiment, information (data) and
potential information (addr) for determining oscillation
frequencies at the first and second temperatures are input to the
oscillation-frequency calibrating unit 40.
[0074] In the LUT 41, the capacitance C and the potential V at
which the oscillation frequency F is the fixed oscillation
frequency F0 with respect to temperature are stored in association
with each other based on the information (data) and the potential
information (addr) corresponding to the first and second
temperatures.
[0075] FIG. 22 is a diagram for explaining a control signal after
the shipment of the DCO. In FIG. 22, the capacitance C is recorded
in the LUC 41. The current source 43 generates a control signal for
setting a temperature coefficient from the capacitance C and
outputs the control signal to a capacitor unit 55. A control signal
as a control amount corresponding to an absolute value of the
capacitance C is output to the capacitor unit 55. The capacitor
unit 55 is equivalent to the variable capacitor 51 or the switch 52
explained with reference to FIG. 7. It is assumed that at least one
capacitor unit 55 is set in the LC oscillator. The
oscillation-frequency calibrating unit 40 shown in FIG. 22
functions as an oscillation-frequency compensating unit that
compensates for an oscillation frequency of the DCO 50. By adopting
this configuration, it is possible to perform temperature
compensation for the oscillation frequency with respect to
fluctuation in the temperature T in the DCO 5.
[0076] In the seventh embodiment, the LUT 41 in which the
capacitance C is stored is used for the LC oscillator. However, the
LUT 41 can also be applied to a ring oscillator. In this case, the
capacitance C of the LUT 41 is input to the current source 43. The
current source 43 generates a control signal for setting a
temperature coefficient and an absolute temperature and outputs the
control signal to the transistors 53 and 54 of the DCO 50. As shown
in FIG. 12, the current source 43 can be directly connected to the
ring oscillator without the intervention of the transistors 53 and
54.
[0077] A current value can be used for the information (data) for
controlling the DCO 50 instead of the capacitance C. Specifically,
in the LUT 41, an electric current I and potential V at which the
oscillation frequency F is the fixed oscillation frequency F0 with
respect to temperature are stored in association with each other
based on the information (data) and the potential information
(addr) corresponding to the first and second temperatures. The
current value indicates a magnitude of an electric current from the
current source 43. An oscillation frequency of the ring oscillator
is changed according to the current value. The electric current
from the current source 43 and the oscillation frequency of the
ring oscillator are in a substantially proportional relation. The
oscillation-frequency setting unit 45 sets a temperature
coefficient and an absolute value of the oscillation frequency
referring to the LUT 41. The set temperature coefficient and
absolute value of the oscillation frequency are stored in a storing
unit. The current source 43 generates a control signal
corresponding to the temperature coefficient stored in the storing
unit and outputs the control signal to the capacitor unit 55 of the
DCO 50. The absolute value stored in the storing unit is output to
the capacitor unit 55 as a control signal corresponding to the
absolute value. In this way, even when the current value is used
instead of the capacitance C, it is possible to generate the
control signal for setting the temperature coefficient of the
oscillation frequency.
[0078] The oscillation-frequency calibrating unit 40 shown in FIG.
21 can perform the interpolation processing explained with
reference to FIG. 18. In this case, it is assumed that the
oscillation-frequency calibrating unit 40 shown in FIG. 21 includes
an interpolation processing function of the oscillation-frequency
setting unit 45.
[0079] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
* * * * *