U.S. patent application number 12/350647 was filed with the patent office on 2009-05-21 for current mode bus interface system, method of performing a mode transition and mode control signal generator for the same.
Invention is credited to Dong-Uk Park.
Application Number | 20090132843 12/350647 |
Document ID | / |
Family ID | 37084381 |
Filed Date | 2009-05-21 |
United States Patent
Application |
20090132843 |
Kind Code |
A1 |
Park; Dong-Uk |
May 21, 2009 |
CURRENT MODE BUS INTERFACE SYSTEM, METHOD OF PERFORMING A MODE
TRANSITION AND MODE CONTROL SIGNAL GENERATOR FOR THE SAME
Abstract
A current mode bus interface system includes a host interface
device configured to transmit a reference current and a clock
current, and to transmit a data current during a first transfer
mode, and to receive a reverse direction data current and compare
the reverse direction data current with the reference current to
generate a reverse direction data voltage during a second transfer
mode; and a client interface device configured to receive the
reference current and the clock current and compare the reference
current with the clock current to generate a clock voltage, to
receive the data current and compare the data current with the
reference current to generate a data voltage during the first
transfer mode, and to transmit the reverse direction data current
through a conducting wire over which the data current is received
during the second transfer mode.
Inventors: |
Park; Dong-Uk; (Seoul,
KR) |
Correspondence
Address: |
F. CHAU & ASSOCIATES, LLC
130 WOODBURY ROAD
WOODBURY
NY
11797
US
|
Family ID: |
37084381 |
Appl. No.: |
12/350647 |
Filed: |
January 8, 2009 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
11357550 |
Feb 17, 2006 |
7492189 |
|
|
12350647 |
|
|
|
|
Current U.S.
Class: |
713/323 |
Current CPC
Class: |
G06F 13/4072
20130101 |
Class at
Publication: |
713/323 |
International
Class: |
G06F 1/32 20060101
G06F001/32 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 8, 2005 |
KR |
2005-19050 |
Claims
1. A method of performing a mode transition in a current mode bus
interface system, the method comprising: cutting off transmitted
currents from a host when the host enters into a suspend mode in
response to a sleep request from the host; causing a client to
enter into a suspend mode when the client senses the cut-off of the
transmitted currents; and causing the host or the client to perform
a transition from the suspend mode to a normal operation mode in
response to a wake-up request from the host or the client.
2. The method of claim 1, wherein the transmitted currents comprise
a reference current, a clock current and a data current, and
wherein the client enters into the suspend mode when the client
senses the cut-off of the reference current.
3. The method of claim 2, wherein causing the host and the client
to perform the transition comprises: transmitting the reference
current from the host in response to the wake-up request of the
host, and wherein the client performs the transition from the
suspend mode to the normal operation mode when the client senses
the reference current transmitted from the host.
4. The method of claim 3, wherein the host transmits the clock
current and the data current after the client performs the
transition from the suspend mode to the normal operation mode.
5. The method of claim 2, wherein causing the host and the client
to perform the transition comprises: transmitting a reverse
direction data current having a predetermined level from the client
in response to the wake-up request from the client; and
transmitting the reference current to the client after the host
senses the reverse direction data current received from the client,
and wherein the client performs the transition from the suspend
mode to the normal operation mode when the client senses the
reference current transmitted from the host.
6. The method of claim 5, wherein the host transmits the clock
current and the data current after the client performs the
transition from the suspend mode to the normal operation mode.
7. The method of claim 2, wherein causing the host and the client
to perform the transition comprises: transmitting the reference
current to the client from the host in response to the wake-up
request from the host; transmitting the reverse direction data
current to the host from the client via a conducting wire over
which the data current is received, in response to the wake-up
request of the client; and causing the client to perform a
transition from the suspend mode to a forward direction transfer
mode after the client stops the transmission of the reverse
direction data current when the client senses the reference current
transmitted from the host.
8. The method of claim 7, wherein the host transmits the clock
current and the data current after the client stops the
transmission of the reverse direction data current to the host and
performs the transition from the suspend mode to the forward
direction transfer mode.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a divisional application of co-pending U.S.
application Ser. No. 11/357,550, filed Feb. 17, 2006, which claims
foreign priority under 35 U.S.C. .sctn. 119 to Korean Patent
Application No. 2005-19050 filed Feb. 17, 2006, which is hereby
incorporated by reference for all purposes as if fully set forth
herein.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The present invention relates to a bus interface system, and
more particularly to a current mode bus interface system that
transmits/receives data currents.
[0004] 2. Discussion of Related Art
[0005] Generally, to transmit/receive signals between integrated
circuits, either a voltage mode transmitting/receiving operation or
a current mode transmitting/receiving operation is performed. Since
the voltage mode transmitting/receiving operation introduces a
resistive-capacitive delay when transmitting/receiving signals, the
current mode transmitting/receiving operation has been studied to
reduce the resistive-capacitive delay.
[0006] In the current mode transmitting/receiving operation, a
current of a transmitted/received signal is observed. In
particular, the current mode transmitting/receiving operation
maintains a voltage level of a transmission line at a predetermined
level, and transfers data by changing a level of a current flowing
through the transmission line. For example, a transmitter may
sequentially transfer digital data using two logic levels `1` and
`0`. Thus, a current level of about 17 mA through 23 mA may be set
to the logic level `1`, and a current level of about 0 mA through 6
mA may be set to the logic level `0`. A receiver may then recover
the transmitted digital data by determining the current level of
the transmitted signals. Since the voltage level is maintained at
the predetermined level during the current mode
transmitting/receiving operation, a resistive-capacitive delay may
be reduced.
[0007] In a `pseudo-differential current mode`
transmitting/receiving operation, the transmitter may transmit a
reference current with a data current. For example, the transmitter
may set the current level of about 17 mA through 23 mA to the logic
level `1`, set the current level of about 0 mA through 6 mA to the
logic level `0`, and transmit the data current based on the set
logic levels. At the same time, the transmitter may transmit a
reference current of about 10 mA. The receiver receives both the
data current and the reference current, compares a magnitude of the
data current with that of the reference current, and then
determines the logic level of the transmitted data current. Thus,
for example, when the magnitude of the data current is larger is
than that of the reference current, the transmitted digital data is
the logic level `1`, and when the magnitude of the data current is
smaller than that of the reference current, the transmitted digital
data is the logic level `0`.
[0008] In a device embodying a mobile application such as a
portable phone, a bus interface can be used to aid in the reduction
of power consumption. For example, by causing the bus interface and
other components of the device to enter into a suspend mode when
they are not being used, the power consumed by the device may be
reduced. Accordingly, as various applications and devices such as a
mobile phone and a digital camera continue to become integrated,
the need to support bidirectional data transfer between a digital
camera module and a mobile phone module is increasing. However,
because the bus interface is increasingly being used in such
devices, the ability to conserve power is lessened. As such, a need
exists for a bus interface system that is capable of performing a
bidirectional data transfer between a host and a client while
reducing power consumption.
SUMMARY OF THE INVENTION
[0009] In an embodiment of the present invention, a current mode
bus interface system includes: a host interface device configured
to transmit a reference current and a clock current, and to
transmit a data current during a first transfer mode, and to
receive a reverse direction data current and compare the reverse
direction data current with the reference current to generate a
reverse direction data voltage during a second transfer mode; and a
client interface device configured to receive the reference current
and the clock current and compare the reference current with the
clock current to generate a clock voltage, to receive the data
current and compare the data current with the reference current to
generate a data voltage during the first transfer mode, and to
transmit the reverse direction data current through a conducting
wire over which the data current is received during the second
transfer mode.
[0010] In another embodiment of the present invention, a current
mode host interface device includes: a reference current
transmitter configured to transmit a reference current; a clock
current transmitter configured to transmit a clock current that
periodically changes; and a data transmitter/receiver configured to
transmit a data current during a forward direction transfer mode,
and to receive a reverse direction data current through a
conducting wire over which the data current is transmitted and
compare the reference current with the reverse direction data
current to generate a reverse direction data voltage during a
reverse direction transfer mode.
[0011] The current mode host interface device may cut off the
reference current and cause the clock current and the data current
to enter into a suspend mode in response to a sleep request. The
current mode host interface device may perform a transition from
the suspend mode to a normal operation mode in response to the
wake-up request, or when a reception of the reverse direction data
current having a predetermined level is sensed. The current mode
host interface device may transmit the reference current to the
current mode client interface device when the current mode host
interface device performs the transition from the suspend mode to
the normal operation mode, and may transmit the clock current and
the data current after the current mode client interface device
performs the transition from the suspend mode to the normal
operation mode.
[0012] In yet another embodiment of the present invention, a
current mode client interface device includes: a clock voltage
generator configured to receive a reference current and a clock
current that periodically changes and compare the reference current
with the clock current to generate a clock voltage; and a data
transmitter/receiver configured to receive a data current and
compare the reference current with the data current to generate a
data voltage during a forward direction transfer mode, and to
transmit a reverse direction data current through a conducting wire
over which the data current is received during a reverse direction
transfer mode.
[0013] The current mode client interface device may further include
a mode control signal generator configured to sense the reference
current to generate a mode control signal.
[0014] In another embodiment of the present invention, a method of
performing a mode transition in a current mode bus interface system
includes: cutting off transmitted currents from a host when the
host enters into a suspend mode in response to a sleep request from
the host; causing a client to enter into a suspend mode when the
client senses the cut-off of the transmitted currents; and causing
the host or the client to perform a transition from the suspend
mode to a normal operation mode in response to a wake-up request
from the host or the client.
[0015] The normal operation mode includes a forward direction
transfer mode and a reverse direction transfer mode. The
transmitted currents may include a reference current, a clock
current and a data current, and the client may enter into the
suspend mode when the client senses the cut-off of the reference
current. Both the host and the client may generate the wake-up
request to perform the transition from the suspend mode to the
normal operation mode.
[0016] In yet another embodiment of the present invention, a mode
control signal generator of a current mode bus interface system
includes: a received current copier configured to copy a received
current to generate a copied received current; a comparing current
generator configured to generate a comparing current having a
magnitude smaller than a magnitude of the received current; a
current comparator configured to compare the copied received
current with the comparing current to generate a comparison signal;
and a noise cancellation unit configured to cancel a noise
component included in the comparison signal to generate a mode
control signal.
[0017] The received current may be a reference current transmitted
from a host of the current mode bus interface system. The comparing
current may be generated by using the reference current stored as a
digital value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and other features of the present invention will
become more apparent by describing in detail exemplary embodiments
thereof with reference to the attached drawings in which like
reference numbers refer to like elements throughout:
[0019] FIG. 1 is a block diagram illustrating a current mode bus
interface system according to an exemplary embodiment of the
present invention;
[0020] FIG. 2 is a block diagram illustrating a current mode host
interface device shown in FIG. 1;
[0021] FIG. 3 is a block diagram illustrating a current mode client
interface device shown in FIG. 1;
[0022] FIG. 4 is a block diagram illustrating a mode control signal
generator shown in FIG. 3;
[0023] FIG. 5A shows a waveform having a noise component;
[0024] FIG. 5B shows a waveform having a noise component;
[0025] FIG. 6 is a circuit diagram illustrating a noise
cancellation circuit shown in FIG. 4 according to an exemplary
embodiment of the present invention;
[0026] FIG. 7 is a circuit diagram illustrating the noise
cancellation circuit shown in FIG. 4 according to another exemplary
embodiment of the present invention;
[0027] FIG. 8 is a timing diagram illustrating a transition from a
normal operation mode to a suspend mode according to an exemplary
embodiment of the present invention; and
[0028] FIGS. 9 through 11 are timing diagrams illustrating
transitions from a suspend mode to a normal operation mode
according to other exemplary embodiments of the present
invention.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0029] Hereinafter, exemplary embodiments of the present invention
will be explained in detail with reference to the accompanying
drawings. However, specific structural and functional details
disclosed herein are merely presented for purposes of describing
the exemplary embodiments of the present invention.
[0030] It will be understood that, although the terms first,
second, etc. may be used herein to describe various elements, these
elements should not be limited by these terms. These terms are used
to distinguish one element from another. For example, a first
element could be termed a second element, and, similarly, a second
element could be termed a first element, without departing from the
scope of the present invention. As used herein, the term "and/or"
includes any and all combinations of one or more of the associated
listed items.
[0031] It will also be understood that when an element is referred
to as being "connected" or "coupled" to another element, it can be
directly connected or coupled to the other element or intervening
elements may be present. In contrast, when an element is referred
to as being "directly connected" or "directly coupled" to another
element, there are no intervening elements present. Other words
used to describe the relationship between elements should be
interpreted in a like fashion (e.g., "between" versus "directly
between", "adjacent" versus "directly adjacent", etc.).
[0032] The terminology used herein is for the purpose of describing
particular embodiments and is not intended to be limiting of the
invention. As used herein, the singular forms "a", "an" and "the"
are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises", "comprising", "includes" and/or
"including", when used herein, specify the presence of stated
features, integers, steps, operations, elements, and/or components,
but do not preclude the presence or addition of one or more other
features, integers, steps, operations, elements, components, and/or
groups thereof.
[0033] FIG. 1 is a block diagram illustrating a current mode bus
interface system 100 according to an exemplary embodiment of the
present invention.
[0034] Referring to FIG. 1, the current mode bus interface system
100 includes a current mode host interface device 110 and a current
mode client interface device 120. Hereinafter, the current mode
host interface device 110 and the current mode client interface
device 120 may be referred to as a host 110 and a client 120,
respectively.
[0035] The current mode host interface device 110 transmits a
reference current IREF and a clock current ICLK to the current mode
client interface device 120. The current mode host interface device
110 also transmits a data current IDATA to the current mode client
interface device 120 during a forward direction transfer mode. The
current mode host interface device 110 receives a reverse direction
data current IR_DATA from the current mode client interface device
120 and compares the reverse direction data current IR_DATA with
the reference current IREF to generate a reverse direction data
voltage.
[0036] The current mode client interface device 120 receives the
reference current IREF and the clock current ICLK from the current
mode host interface device 110, and compares the reference current
IREF with the clock current ICLK to generate a clock voltage. The
current mode client interface device 120 receives the data current
IDATA from the current mode host interface device 110 during the
forward direction transfer mode, and compares the data current
IDATA with the reference current IREF to generate a data voltage.
In addition, the current mode client interface device 120 transmits
the reverse direction data current IR_DATA to the current mode host
interface device 110 through a conducting wire over which the data
current IDATA is received during a reverse direction transfer
mode.
[0037] As shown, for example, in FIG. 1, when the clock current
ICLK, the data current IDATA and the reverse direction data current
IR_DATA have a current level of about 300 .mu.A they may be set to
a logic `high` level, and when other currents have a current level
of about 100 .mu.A they may be set to a logic `low` level. The
reference current IREF may have a current level of about 200 .mu.A
and since the amount of data transferred from the client 120 to the
host 110 is typically smaller than that transferred from the host
110 to the client 120 the reverse direction data current IR_DATA
may have a frequency lower than that of the data current IDATA.
[0038] FIG. 2 is a block diagram illustrating the current mode host
interface device 110 shown in FIG. 1.
[0039] Referring to FIG. 2, the current mode host interface device
110 includes a reference current transmitter 210, a clock current
transmitter 220 and a data transmitter/receiver 230.
[0040] The reference current transmitter 210 transmits the
reference current IREF. The reference current transmitter 210
includes a current source 211 for generating the reference current
IREF.
[0041] The reference current IREF generated by the current source
211 may flow to the host 110 from the client 120, or to the client
120 from the host 110.
[0042] The clock current transmitter 220 transmits the clock
current ICLK. The clock current transmitter 220 includes a low
current source 221, a differential current source 222 and a clock
control switch 223.
[0043] The low current source 221 provides a low current ILOW
having half a magnitude of the reference current IREF. The
differential current source 222 provides a differential current
IDIFF substantially identical to the magnitude of the reference
current IREF.
[0044] The clock control switch 223 transmits the clock current
ICLK, identical to a magnitude of the low current ILOW or identical
to a magnitude of a sum of the low current ILOW and the
differential current IDIFF, based on a clock control signal
TXCLK.
[0045] For example, the reference current IREF and the differential
current IDIFF may have a current level of about 200 .mu.A
respectively. The low current ILOW may have a current level of
about 100 .mu.A. Consequently, the clock current ICLK may have a
current level of about 100 .mu.A or 300 .mu.A.
[0046] The data transmitter/receiver 230 transmits the data current
IDATA during the forward direction transfer mode, and receives the
reverse direction data current IR_DATA during the reverse direction
transfer mode and compares the reference current REF with the
reverse direction data current IR_DATA to generate a reverse
direction data voltage TXRDATA.
[0047] The data transmitter/receiver 230 includes switches 231 and
232, a data current transmitter and a data current receiver.
[0048] The switch 231 is closed during the forward direction
transfer mode, and is opened during the reverse direction transfer
mode.
[0049] Contrary to the switch 231, the switch 232 is closed during
the reverse direction transfer mode, and is opened during the
forward direction transfer mode.
[0050] The data current transmitter transmits the data current
IDATA via the switch 231 during the forward direction transfer
mode.
[0051] The data current transmitter includes a low current source
233, a differential current source 234 and a data control switch
235.
[0052] The low current source 233 provides a low current ILOW
having half the magnitude of the reference current IREF.
[0053] The differential current source 234 provides a differential
current IDIFF substantially identical to the magnitude of the
reference current IREF.
[0054] The data control switch 235 transmits the data current
IDATA, identical to a magnitude of the low current ILOW or
identical to a magnitude of a sum of the low current ILOW and the
differential current IDIFF, based on a data control signal
TXDATA.
[0055] For example, the reference current IREF and the differential
current IDIFF may have a current level of about 200 .mu.A,
respectively. The low current ILOW may have a current level of
about 100 .mu.A. Consequently, the data current IDATA may have a
current level of about 100 .mu.A or 300 .mu.A.
[0056] The data current receiver receives the reverse direction
data current IR_DATA via the switch 232 during the reverse
direction transfer mode and then generates the reverse direction
data voltage TXRDATA.
[0057] The data current receiver includes a reference current
copier 236, a data current copier 237 and a current comparator
238.
[0058] The reference current copier 236 copies the reference
current IREF to generate a copied reference current IREF.
[0059] The data current copier 237 copies the reverse direction
data current IR_DATA to generate a copied reverse direction data
current IR_DATA.
[0060] The reference current copier 236 and the data current copier
237 may be implemented by using a current mirror.
[0061] The current comparator 238 compares the copied reference
current IREF with the copied reverse direction data current IR_DATA
to generate the reverse direction data voltage TXRDATA.
[0062] The current comparator 238 may be implemented by using
various methods known to one of ordinary skill in the art. For
example, the current comparator 238 may be an operational
amplifier.
[0063] As shown in FIG. 2, the current mode host interface device
110 may cut off the reference current IREF, the clock current ICLK
and the data current IDATA to enter into a suspend mode in response
to a sleep request. When the current mode host interface device 110
is in the suspend mode it may perform a transition from the suspend
mode to a normal operation mode when a wake-up request occurs or
when the reverse direction data current IR_DATA having a
predetermined current level is detected.
[0064] When the current mode host interface device 110 performs the
transition from the suspend mode to the normal operation mode, the
current mode host interface device 110 transmits the reference
current IREF to the current mode client interface device 120, and
then, transmits the clock current ICLK and the data current IDATA
after the current mode client interface device 120 completes the
transition from the suspend mode to the normal operation mode.
[0065] FIG. 3 is a block diagram illustrating the current mode
client interface device 120 shown in FIG. 1.
[0066] Referring to FIG. 3, the current mode client interface
device 120 includes a clock voltage generator 310 and a data
transmitter/receiver 320. The current mode client interface device
120 may further include a mode control signal generator 330.
[0067] The clock voltage generator 310 receives the reference
current IREF and the clock current ICLK, which may change
periodically, and compares the reference current IREF with the
clock current ICLK to generate a clock voltage RXCLK.
[0068] The clock voltage generator 310 includes a reference current
copier 340, a clock current copier 311 and a current comparator
312.
[0069] The reference current copier 340 copies the reference
current IREF to generate a copied reference current IREF.
[0070] The reference current copier 340 may be implemented by using
a current mirror, and may provide the copied reference current IREF
to the current comparator 312, the data transmitter/receiver 320
and the mode control signal generator 330.
[0071] The clock current copier 311 copies the clock current ICLK
to generate a copied clock current ICLK, and may be implemented by
using a current mirror.
[0072] The current comparator 312 compares the copied reference
current IREF with the copied clock current ICLK to generate the
clock voltage RXCLK.
[0073] The data transmitter/receiver 320 receives the data current
IDATA during the forward direction transfer mode and compares the
reference current IREF with the data current IDATA to generate a
data voltage RXDATA.
[0074] The data transmitter/receiver 320 transmits the reverse
direction data current IR_DATA through a conducting wire over which
the data current IDATA is received during the reverse direction
transfer mode.
[0075] The data transmitter/receiver 320 includes switches 321 and
322, a data current transmitter and a data current receiver.
[0076] The switch 321 is closed during the forward direction
transfer mode, and is opened during the reverse direction transfer
mode.
[0077] Contrary to the switch 321, the switch 322 is closed during
the reverse direction transfer mode, and is opened during the
forward direction transfer mode.
[0078] The data current transmitter transmits the reverse direction
data current IR_DATA via the switch 322 during the reverse
direction transfer mode.
[0079] The data current transmitter includes a low current source
323, a differential current source 324 and a data control switch
325.
[0080] The low current source 323 provides a low current ILOW
having half a magnitude of the reference current IREF.
[0081] The differential current source 324 provides a differential
current IDIFF substantially identical to the magnitude of the
reference current IREF.
[0082] The low current source 323 and the differential current
source 324 may be generated by using the reference current IREF
stored as a digital value to prevent a mismatch between a current
quantity provided from the current mode client interface device 120
and a current quantity being considered by the current mode host
interface device 110.
[0083] For example, due to temperature variations, manufacturing
process variations and supply voltage variations, the current mode
host interface device 110 may not be able to distinguish data
included in the reverse direction data current IR_DATA received
from the current mode client interface device 120 by using the
reference current IREF. To prevent this, the low current source 323
and the differential current source 324 may be generated by using
the reference current IREF stored as a digital value. In
particular, when the reference current IREF is stored as the
digital value, an unnecessary current flow may be prevented Still
referring to FIG. 3, the data control switch 325 transmits the
reverse direction data current IR_DATA, identical to a magnitude of
the low current ILOW or identical to a magnitude of a sum of the
low current ILOW and the differential current IDIFF, based on a
reverse direction data control signal RXRDATA.
[0084] For example, the reference current IREF and the differential
current IDIFF may have a current level of about 200 .mu.A,
respectively. The low current ILOW may have a current level of
about 100 .mu.A. Consequently, the reverse direction data current
IR_DATA may have a current level of about 100 .mu.A or 300
.mu.A.
[0085] The data current receiver receives the data current IDATA
via the switch 321 during the forward direction transfer mode and
then generates the data voltage RXDATA.
[0086] The data current receiver includes the reference current
copier 340, a data current copier 326 and a current comparator
327.
[0087] The reference current copier 340 copies the reference
current IREF to generate a copied reference current IREF. The data
current copier 326 copies the data current IDATA to generate a
copied reverse data current IDATA.
[0088] The reference current copier 340 and the data current copier
326 may be implemented by using a current mirror.
[0089] The current comparator 327 compares the copied reference
current IREF with the copied data current DATA to generate the data
voltage RXDATA. The current comparator 327 may be implemented by
using various methods known to one of ordinary skill in the art.
For example, the current comparator 327 may be an operational
amplifier.
[0090] The mode control signal generator 330 generates a mode
control signal RXPD according to whether the reference current IREF
is allowed to flow from the host 110 or is cut off by the host 110.
For example, the mode control signal generator 330 may change a
state of the mode control signal RXPD to a logic `high` level when
the reference current IREF is allowed to flow from the host 110,
and may change the state of the mode control signal RXPD to a logic
`low` level when the reference current IREF is cut off by the host
110.
[0091] The mode control signal. generator 330 of FIG. 3 may be
included in the current mode host interface device 110 as well as
the current mode client interface device 120. In such a case, the
current mode host interface device 110 may detect a current
transferred from the current mode client interface device 120 to
control its transition between the normal operation mode and the
suspend mode.
[0092] FIG. 4 is a block diagram illustrating the mode control
signal generator 330 shown in FIG. 3.
[0093] Referring to FIG. 4, the mode control signal generator 330
includes a reference current copier (not shown), a comparing
current generator 410, a current comparator 420, and a noise
cancellation unit 430.
[0094] The reference current copier copies the reference current
IREF to generate a copied reference current IREF. Although not
shown, the reference current copier may be implemented by using a
current mirror, and may be included in or the same as the reference
current copier 340 shown in FIG. 3.
[0095] The comparing current generator 410 generates a comparing
current IPDS having a magnitude smaller than the reference current
IREF.
[0096] When the magnitude of the comparing current IPDS is smaller
than the magnitude of the reference current IREF, a current
consumed during the normal operation mode may be reduced and power
consumption may thereby be reduced. However, when the magnitude of
the comparing current IPDS is much smaller than the magnitude of
the reference current IREF, the magnitude of the comparing current
IPDS should be determined to be at a level such that a noise
characteristic of a comparison signal is not degraded. For example,
the level of the comparing current IPDS may be determined by
performing a simulation.
[0097] The comparing current generator 410 may be implemented by
using a diode coupled CMOS transistor, or by using a current
mirror.
[0098] The comparing current IPDS is generated by using the
reference current IREF and may correspond to a predetermined ratio
of the reference current IREF. For example, the comparing current
IPDS may correspond to about 10% of the reference current IREF. The
comparing current generator 410 may also generate the comparing
current IPDS by using the reference current IREF stored as a
digital value.
[0099] Still referring to FIG. 4, the current comparator 420
compares the copied reference current IREF with the comparing
current IPDS to generate the comparison signal. For example, when
the reference current IREF is allowed to flow from the host 110, a
state of the comparison signal is a logic `high` level, and when
the reference current IREF is cut off by the host 110, the state of
the comparison signal is a logic `low` level.
[0100] The current comparator 420 may be implemented by using
various methods known to one of ordinary skill in the art. For
example, the current comparator 420 may be an operational
amplifier.
[0101] The comparing current generator 410 allows the comparing
current IPDS to flow when the reference current IREF is allowed to
flow from the host 110, and does not allow the comparing current
IPDS to flow, to reduce power consumption during the suspend mode,
when the reference current IREF is cut off by the host 110.
[0102] The noise cancellation unit 430 cancels a noise component
included in the comparison signal to generate the mode control
signal RXPD of the current mode client interface device 120.
[0103] The noise cancellation unit 430 is used to cancel noise
included in signals transmitted, for example, through a current
mode bus interface of the current mode bus interface system 100,
thus preventing the current mode bus interface system 100 from
operating abnormally.
[0104] The mode control signal RXPD may also be used for
controlling the transition between the normal operation mode and
the suspend mode of the current mode client interface device 120.
For example, the current mode client interface device 120 may
operate in the normal operation mode when the mode control signal
RXPD is at the logic `high` level, and the current mode client
interface device 120 may operate in the suspend mode when the mode
control signal RXPD is at the logic `low` level.
[0105] Hereinafter, operations of the mode control signal generator
330 shown in FIG. 4 will be explained.
[0106] When the current mode host interface device 110 performs the
transition from the normal operation mode to the suspend mode and
cuts off the reference current REF, the current comparator 420
senses the cut-off of the reference current IREF by using the
comparing current IPDS. When the current comparator 420 senses the
cut-off of the reference current IREF to generate the comparison
signal, the noise cancellation unit 430 cancels the noise component
included in the comparison signal to generate the mode control
signal RXPD.
[0107] Additionally, when the current mode host interface device
110 performs the transition from the suspend mode to the normal
operation mode and allows the reference current IREF to flow to the
client 120, the current comparator 420 senses the flow of the
reference current IREF by using the comparing current IPDS and
generates the mode control signal RXPD through the noise
cancellation unit 430.
[0108] The noise cancellation unit 430 includes a Schmitt trigger
circuit 431 and a noise cancellation circuit 432.
[0109] The Schmitt trigger circuit 431 cancels the noise component
having a voltage level smaller than a predetermined voltage level
included in the comparison signal.
[0110] The noise cancellation circuit 432 cancels the noise
component of a short pulse region included in the comparison
signal.
[0111] FIG. 5A is a waveform diagram illustrating noise cancelled
by the Schmitt trigger circuit 431 according to an exemplary
embodiment of the present invention.
[0112] As shown in FIG. 5A, a noise component 510 having the
voltage level smaller than the predetermined voltage level included
in the comparison signal is cancelled by the Schmitt trigger
circuit 431.
[0113] FIG. 5B is a waveform diagram illustrating noise cancelled
by a noise cancellation circuit 432 according to another exemplary
embodiment of the present invention.
[0114] As shown in FIG. 5B, a noise component 520 of a short pulse
region included in the comparison signal is cancelled by the noise
cancellation circuit 432.
[0115] FIG. 6 is a circuit diagram illustrating the noise
cancellation circuit 432 shown in FIG. 4 according to an exemplary
embodiment of the present invention.
[0116] Referring to FIG. 6, the noise cancellation circuit 432
includes a CMOS inverter. The noise cancellation circuit 432
controls an aspect ratio (W/L) of a PMOS transistor 610
constituting the CMOS inverter to cancel a noise component of a
short pulse region.
[0117] FIG. 7 is a circuit diagram illustrating the noise
cancellation circuit 432 shown in FIG. 4 according to another
exemplary embodiment of the present invention.
[0118] Referring to FIG. 7, the noise cancellation circuit 432
includes a delay section 710 and an AND gate 720.
[0119] The delay section 710 delays the comparison signal. The AND
gate 720 performs a logical operation on the comparison signal and
the comparison signal delayed by the delay section 710 to generate
the mode control signal RXPD.
[0120] Accordingly, the noise cancellation circuit 432 shown in
FIG. 7 may cancel a noise component of a pulse region shorter than
a delayed time period of the delay section 710.
[0121] FIG. 8 is a timing diagram illustrating a transition from a
normal operation mode to a suspend mode according to an exemplary
embodiment of the present invention.
[0122] Referring to FIG. 8, a host mode control signal TXPD drops
to the logic `low` level from the logic `high` level in response to
a sleep request from the current mode host interface device
110.
[0123] When the host mode control signal TXPD drops to the logic
`low` level, the current mode host interface device 110 cuts off
the reference current IREF, the clock current ICLK and the data
current IDATA.
[0124] A time period `tpd` refers to a time during which the host
mode control signal TXPD drops to the logic `low` level from the
logic `high` level, and to a time during which the current mode
host interface device 110 cuts off the reference current IREF, the
clock current ICLK and the data current IDATA.
[0125] When the reference current IREF, the clock current ICLK and
the data current IDATA are cut off, the current mode client
interface device 120 senses the cut off and drops the client mode
control signal RXPD to the logic `low` level. When the client mode
control signal RXPD is at the logic `low` level, the current mode
client interface device 120 enters into the suspend mode and does
not consume current.
[0126] In other words, the current mode client interface device 120
powers down each module therein to prevent power consumption when
the client mode control signal RXPD is at the logic `low` level. It
is to be understood that although the current mode client interface
device 120 may sense the cut-off of the reference current IREF, the
clock current ICLK and the data current IDATA and enter into the
suspend mode, the current mode client interface device 120 may
sense the cut-off of one of the reference current IREF, the clock
current ICLK and the data current IDATA and enter into the suspend
mode. For example, the current mode client interface device 120 may
sense the cut-off of the reference current IREF and enter into the
suspend mode.
[0127] When the current mode host interface device 110 enters into
the suspend mode, each of the modules generating the reference
current IREF, the clock current ICLK and the data current IDATA
enters into a sleep mode and thus power consumption does not occur.
At this time, some of the modules may consume power to sense a
wake-up signal when it is received from the current mode client
interface device 120. For example, when the current mode host
interface device 110 is in the suspend mode, the data current
receiver may remain activated to sense the reverse direction data
current having a predetermined level. In addition, when the current
mode host interface device 110 includes the mode control signal
generator 330, the mode control signal generator 330 may remain
activated to sense the wake-up signal when it is received from the
current mode client interface device 120 during the suspend
mode.
[0128] When the current mode client interface device 120 enters
into the suspend mode, the clock voltage generator 310 and the data
transmitter/receiver 320 enter into the sleep mode, and thus the
clock voltage generator 310 and the data transmitter/receiver 320
do not consume power. At this time, the mode control signal
generator 330 included in the current mode client interface device
120 may remain activated to sense the wake-up signal when it is
received from the current mode host interface device 110.
[0129] FIGS. 9 through 11 are timing diagrams illustrating
transitions from a suspend mode to a normal operation mode
according to another exemplary embodiment of the present
invention.
[0130] In FIGS. 9 through 11, the timing diagrams of the control
signals TXPD and RXPD represent a voltage level, and the timing
diagrams of the reference current IREF, the clock current ICLK, the
data current IDATA and the reverse direction data current IR_DATA
represent a current level.
[0131] FIG. 9 is a timing diagram illustrating a transition from
the suspend mode to the normal operation mode of the current mode
bus interface system 100 in response to a wake-up request from the
current mode host interface device 110.
[0132] Referring to FIG. 9, a state of the host mode control signal
TXPD is changed from the logic `low` level to the logic `high`
level in response to a wake-up request from the current mode host
interface device 110.
[0133] When the state of the host mode control signal TXPD is
changed from the logic `low` level to the logic `high` level, the
current mode host interface device 110 allows the reference current
IREF that was cut off to flow to the client 120.
[0134] When the reference current IREF is allowed to flow to the
client 120, the current mode client interface device 120 senses the
reference current IREF to change a state of the client mode control
signal RXPD from the logic `low` level to the logic `high`
level.
[0135] When the state of the client mode control signal RXPD is
changed from the logic `low` level to the logic `high` level, the
current mode client interface device 120 activates internal modules
that were in the sleep mode and is changed to the normal operation
mode.
[0136] The current mode host interface device 110 transmits the
clock current ICLK and the data current IDATA after the current
mode client interface device 120 is changed to the normal operation
mode and is then ready to receive currents. In other words, the
state of the client mode control signal RXPD is changed to the
logic `high` level from the logic `low` level within the time
period `ttxa` shown in FIG. 9.
[0137] The time period `ttxa` refers to a time during which the
current mode host interface device 110 allows the reference current
IREF to again flow to the client 120, and to a time during which
the current mode host interface device 110 allows the clock current
ICLK and the data current IDATA to again flow to the client
120.
[0138] After a time period `trxs` has begun to elapse, which
occurs, for example, immediately after the time period `ttxa`, the
waveforms of the clock current ICLK and the data current IDATA are
changed.
[0139] FIG. 10 is a timing diagram illustrating a transition from
the suspend mode to the normal operation mode of the current mode
bus interface system 100 in response to a wake-up request from the
current mode client interface device 120.
[0140] Referring to FIG. 10, the client mode control signal RXPD is
changed to the logic `high` level from the logic `low` level in
response to the wake-up request from the current mode client
interface device 120.
[0141] When the state of the client mode control signal RXPD is
changed to the logic `high` level from the logic `low` level, the
current mode client interface device 120 allows the reverse
direction data current IR_DATA to flow to the host 110. At this
time, the reverse direction data current IR_DATA may be the logic
`low` level or the logic `high` level. The reverse direction data
current IR_DATA has a level sensed by the current mode host
interface device 110 by using the reference current IREF.
[0142] When the reverse direction data current IR_DATA is allowed
to flow to the host 110, the current mode host interface device 110
senses the flow of the reverse direction data current IR_DATA to
change the host mode control signal TXPD to the logic `high` level
from the logic `low` level. The current mode host interface device
110 may sense the reverse direction data current IR_DATA by using
the mode control signal generator 330.
[0143] When the state of the host mode control signal TXPD is
changed to the logic `high` level, the current mode host interface
device 110 allows the reference current IREF that was cut off to
flow to the client 120.
[0144] When the flow of the reference current IREF is started, the
current mode client interface device 120 senses the reference
current REF and activates internal modules that were in the sleep
mode to perform the transition to the normal operation mode. At
this time, the current mode client interface device 120 stops to
transmit the reverse direction data current IR_DATA to the host
110, and changes the transfer mode of the data transmitter/receiver
320 to the forward direction transfer mode.
[0145] The current mode host interface device 110 transmits the
clock current ICLK and the data current IDATA after the current
mode client interface device 120 is changed to the forward
direction transfer mode and is ready to receive transmitted
currents. In other words, the current mode client interface device
120 is changed to the forward direction transfer mode within the
time period `ttxa` shown in FIG. 10.
[0146] The time period `ttxa` refers to a time during which the
current mode host interface device 110 allows the reference current
IREF that was cut off to again flow to the client 120, and to a
time during which the current mode host interface device 110 allows
the clock current ICLK and the data current IDATA to again flow to
the client 120. A time period `trxd` refers to a time during which
the current mode host interface device 110 allows the reference
current IREF that was cut off to again flow to the client 120, and
to a time during which the current mode client interface device 120
cuts off the reverse direction data current IR_DATA.
[0147] FIG. 11 is a timing diagram illustrating a transition to a
normal operation mode of the current mode interface system 100 when
the current mode host interface device 110 and the current mode
client interface device 120 nearly simultaneously generate a
wake-up request.
[0148] Referring to FIG. 11, the state of the client mode control
signal RXPD is changed to the logic `high` level from the logic
`low` level in response to the wake-up request, and nearly
simultaneously, the state of the host mode control signal TXPD is
changed to the logic `high` level from the logic `low` level in
response to the wake-up request.
[0149] Because the state of the host mode control signal TXPD is
changed to the logic `high` level from the logic `low` level, the
current mode host interface device 110 allows the reference current
IREF to flow to the client 120, and because the state of the client
mode control signal RXPD is changed to the logic `high` level from
the logic `low` level, the current mode client interface device 120
allows the reverse direction data current IR_DATA to flow to the
host 110.
[0150] After the current mode host interface device 110 allows the
reference current IREF to flow to the client 120, the current mode
host interface device 110 senses the reverse direction data current
IR_DATA; however, the current mode host interface device 110 is
changed to the forward direction transfer mode since the current
mode host interface device 110 allows the reference current IREF to
flow to the client 120.
[0151] After the current mode client interface device 120 allows
the reverse direction data current IR_DATA to flow to the client
120, the current mode client interface device 120 senses the
reference current IREF to activate internal modules that were in
the sleep mode, and is changed to the normal operation mode. At
this time, the current mode client interface device 120 stops to
transmit the reverse direction data current IR_DATA to the host 110
and changes the transfer mode of the data transmitter/receiver 320
to the forward direction transfer mode.
[0152] After the transfer mode of the current mode client interface
device 120 is changed to the forward direction transfer mode and
the current mode client interface device 120 is ready to receive
transmitted currents, the current mode host interface device 110
transmits the clock current ICLK and the data current IDATA to the
client 120. In other words, the current mode client interface
device 120 is changed to the forward direction transfer mode from
the reverse direction transfer mode within a time period `ttxa`
shown in FIG. 11. The time period `ttxa` refers to a time during
which the current mode host interface device 110 allows the
reference current IREF that was cut off to again flow to the client
120, and to a time during which the current mode host interface
device 110 allows the clock current ICLK and the data current IDATA
to again flow to the client 120.
[0153] As shown in FIG. 11, a time period `trxd` refers to a time
during which the current mode host interface device 110 allows the
reference current IREF that was cut off to again flow to the client
120, and to a time during which the current mode client interface
device 120 cuts off the reverse direction data current IR_DATA. A
time period `ta` refers to a time during which the current mode
client interface device 120 cuts off the reverse direction data
current IR_DATA, and to the time during which the current mode host
interface device 110 allows the data current IDATA to again flow to
the client 120. The time period `ttxa` should be longer than a sum
of the time period `trxd` and the time period `ta`.
[0154] As described above, the current mode bus interface system
according to an exemplary embodiment of the present invention
includes a current mode host interface device and a current mode
client interface device and is capable of performing a
bidirectional data transfer between the host and the client. For
example, the host is capable of transmitting data to the client and
receiving data from the client, and the client is capable of
transmitting data to the host and receiving data from the host.
[0155] Additionally, the method of performing the mode transition
and the mode control signal generator according to an exemplary
embodiment of the present invention are capable of performing a
transition between a normal operation mode and a suspend mode in
response to a wake-up request generated by the host or the
client.
[0156] Therefore, the exemplary embodiments of the present
invention may be used with various applications employing
bidirectional communication between hosts and clients, and with
low-power applications such as mobile applications and devices such
as portable camera phones, personal digital assistants, etc.
[0157] While the present invention has been particularly shown and
described with reference to exemplary embodiments thereof it will
be understood by those of ordinary skill in the art that various
changes in form and details may be made therein without departing
from the spirit and scope of the present invention as defined by
the following claims.
* * * * *