U.S. patent application number 16/696409 was filed with the patent office on 2021-05-27 for low quiescent current low-dropout regulator (ldo).
The applicant listed for this patent is QUALCOMM Incorporated. Invention is credited to Shamim AHMED, David Eric HAGLAN.
Application Number | 20210157349 16/696409 |
Document ID | / |
Family ID | 1000005579933 |
Filed Date | 2021-05-27 |
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United States Patent
Application |
20210157349 |
Kind Code |
A1 |
AHMED; Shamim ; et
al. |
May 27, 2021 |
LOW QUIESCENT CURRENT LOW-DROPOUT REGULATOR (LDO)
Abstract
A low-dropout (LDO) regulator and an associated method and
apparatus are described. The LDO regulator generally includes a
first transistor coupled between an input voltage node and an
output voltage node of the LDO regulator. The LDO regulator further
includes a first amplifier having an output coupled to a gate of
the first transistor, wherein a feedback path couples the output
voltage node to an input of the first amplifier. The LDO regulator
further includes a second amplifier having an output coupled to an
enable input of the first amplifier, wherein a voltage-sensing path
couples the input voltage node to an input of the second amplifier.
The LDO regulator further includes and a second transistor coupled
between the gate of the first transistor and a reference potential
node, the output of the second amplifier being coupled to a gate of
the second transistor.
Inventors: |
AHMED; Shamim; (Tempe,
AZ) ; HAGLAN; David Eric; (Tempe, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QUALCOMM Incorporated |
San Diego |
CA |
US |
|
|
Family ID: |
1000005579933 |
Appl. No.: |
16/696409 |
Filed: |
November 26, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 1/3827 20130101;
G05F 1/59 20130101; G05F 1/575 20130101 |
International
Class: |
G05F 1/575 20060101
G05F001/575; G05F 1/59 20060101 G05F001/59 |
Claims
1. A circuit for voltage regulation, comprising: a first transistor
coupled between an input voltage node and an output voltage node of
the circuit; a first amplifier having an output coupled to a gate
of the first transistor, wherein a feedback path couples the output
voltage node to an input of the first amplifier; a second amplifier
having an output coupled to an enable input of the first amplifier,
wherein a voltage-sensing path couples the input voltage node to an
input of the second amplifier; and a second transistor coupled
between the gate of the first transistor and a reference potential
node, the output of the second amplifier being coupled to a gate of
the second transistor.
2. The circuit of claim 1, further comprising an inverter coupled
between the output of the second amplifier and the enable input of
the first amplifier.
3. The circuit of claim 1, further comprising a first voltage
divider circuit coupled to the output voltage node, a tap node of
the first voltage divider circuit being coupled to the input of the
first amplifier.
4. The circuit of claim 3, further comprising a second voltage
divider circuit coupled to the input voltage node, a tap node of
the second voltage divider circuit being coupled to the input of
the second amplifier.
5. The circuit of claim 4, wherein a voltage divider ratio of the
first voltage divider circuit is the same as a voltage divider
ratio of the second voltage divider circuit.
6. The circuit of claim 5, further comprising a resistive element
coupled between the second voltage divider circuit and the input
voltage node.
7. The circuit of claim 1, wherein the first transistor comprises a
p-type metal-oxide-semiconductor (PMOS) transistor.
8. The circuit of claim 1, wherein the second transistor comprises
an n-type metal-oxide-semiconductor (NMOS) transistor.
9. The circuit of claim 1, wherein another input of the first
amplifier is coupled to a reference voltage node, and wherein
another input of the second amplifier is coupled to the reference
voltage node.
10. A method for power regulation, comprising: performing a first
comparison, via a first amplifier, of an output voltage with a
reference voltage; regulate, via a first transistor, an input
voltage at an input voltage node to generate the output voltage at
an output voltage node based on the first comparison; performing a
second comparison, via a second amplifier, of the input voltage
with the reference voltage; and shorting, via the first transistor,
the input voltage node to the output voltage node by controlling a
second transistor based on the second comparison.
11. The method of claim 10, wherein shorting the input voltage node
to the output voltage node comprises setting a gate voltage of the
first transistor coupled between the input voltage node and the
output voltage node to a reference potential.
12. The method of claim 11, further comprising disabling the first
amplifier when the gate voltage of the first transistor is set to
the reference potential.
13. The method of claim 10, wherein performing the second
comparison of the input voltage with the reference voltage
comprises comparing a voltage representative of the input voltage
with the reference voltage.
14. The method of claim 10, wherein performing the first comparison
of the output voltage with the reference voltage comprises
comparing a voltage representative of the output voltage with the
reference voltage.
15. The method of claim 10, further comprising disabling the first
amplifier based on the second comparison.
16. An apparatus for power regulation, comprising: means for
performing a first comparison of an output voltage with a reference
voltage; means for regulating an input voltage at an input voltage
node to generate the output voltage at an output voltage node based
on the first comparison; means for performing a second comparison
of the input voltage with the reference voltage; and means for
shorting the input voltage node to the output voltage node by
controlling a second transistor based on the second comparison.
17. The apparatus of claim 16, wherein the means for shorting the
input voltage node to the output voltage node comprises means for
setting a gate voltage of the means for regulating coupled between
the input voltage node and the output voltage node to a reference
potential.
18. The apparatus of claim 17, further comprising means for
disabling the means for performing the first comparison when the
gate voltage of the means for regulating coupled between the input
voltage node and the output voltage node is set to the reference
potential.
19. The apparatus of claim 16, wherein the means for performing the
second comparison of the input voltage with the reference voltage
comprises means for comparing a voltage representative of the input
voltage with the reference voltage.
20. The apparatus of claim 16, wherein the means for performing the
first comparison of the output voltage with the reference voltage
comprises means for comparing a voltage representative of the
output voltage with the reference voltage.
Description
TECHNICAL FIELD
[0001] Certain aspects of the present disclosure generally relate
to electronic circuits and, more particularly, to circuits for
voltage regulation.
BACKGROUND
[0002] A voltage regulator ideally provides a constant direct
current (DC) output voltage regardless of changes in load current
or input voltage. Voltage regulators may be classified as linear
regulators or switching regulators. While linear regulators tend to
be small and compact, many applications may benefit from the
increased efficiency of a switching regulator. A linear regulator
may be implemented by a low-dropout (LDO) regulator, for example. A
switching regulator may be implemented, for example, by a
switched-mode power supply (SMPS), such as a buck converter, a
boost converter, or a buck-boost converter.
[0003] Power management integrated circuits (power management ICs
or PMICs) are used for managing the power requirement of a host
system. A PMIC may be used in battery-operated devices, such as
mobile phones, tablets, laptops, wearables, etc., to control the
flow and direction of electrical power in the devices. The PMIC may
perform a variety of functions for the device such as
direct-current (DC)-to-DC conversion, battery charging,
power-source selection, voltage scaling, power sequencing, etc. For
example, a PMIC may be used for voltage regulation and may feature
an LDO regulator.
SUMMARY
[0004] Certain aspects of the present disclosure generally relate
to a low quiescent current low-dropout (LDO) regulator.
[0005] Certain aspects of the present disclosure provide a circuit
for voltage regulation. The circuit generally includes a first
transistor coupled between an input voltage node and an output
voltage node of the circuit. The circuit further includes a first
amplifier having an output coupled to a gate of the first
transistor, wherein a feedback path couples the output voltage node
to an input of the first amplifier. The circuit further includes a
second amplifier having an output coupled to an enable input of the
first amplifier, wherein a voltage-sensing path couples the input
voltage node to an input of the second amplifier. The circuit
further includes a second transistor coupled between the gate of
the first transistor and a reference potential node, the output of
the second amplifier being coupled to a gate of the second
transistor.
[0006] Certain aspects of the present disclosure provide a method
for power regulation. The method generally includes performing a
first comparison, via a first amplifier, of an output voltage with
a reference voltage, regulate, via a first transistor, an input
voltage at an input voltage node to generate the output voltage at
an output voltage node based on the first comparison, performing a
second comparison, via a second amplifier, of the input voltage
with the reference voltage, and shorting, via the first transistor,
the input voltage node to the output voltage node by controlling a
second transistor based on the second comparison.
[0007] Certain aspects of the present disclosure provide an
apparatus for power regulation. The method generally includes means
for performing a first comparison of the output voltage with a
reference voltage, means for regulating an input voltage at an
input voltage node to generate the output voltage at an output
voltage node based on the first comparison, means for performing a
second comparison of the input voltage with the reference voltage,
and means for shorting the input voltage node to the output voltage
node by controlling a second transistor based on the second
comparison.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] So that the manner in which the above-recited features of
the present disclosure can be understood in detail, a more
particular description, briefly summarized above, may be had by
reference to aspects, some of which are illustrated in the appended
drawings. It is to be noted, however, that the appended drawings
illustrate only certain typical aspects of this disclosure and are
therefore not to be considered limiting of its scope, for the
description may admit to other equally effective aspects.
[0009] FIG. 1 is a block diagram of an example device including a
voltage regulator, according to certain aspects of the present
disclosure.
[0010] FIG. 2 is a schematic diagram of an example low-dropout
(LDO) regulator, in accordance with certain aspects of the present
disclosure.
[0011] FIG. 3 is a flow diagram of example operations for voltage
regulation, in accordance with certain aspects of the present
disclosure.
DETAILED DESCRIPTION
[0012] Various aspects of the disclosure are described more fully
hereinafter with reference to the accompanying drawings. This
disclosure may, however, be embodied in many different forms and
should not be construed as limited to any specific structure or
function presented throughout this disclosure. Rather, these
aspects are provided so that this disclosure will be thorough and
complete, and will fully convey the scope of the disclosure to
those skilled in the art. Based on the teachings herein one skilled
in the art should appreciate that the scope of the disclosure is
intended to cover any aspect of the disclosure disclosed herein,
whether implemented independently of or combined with any other
aspect of the disclosure. For example, an apparatus may be
implemented or a method may be practiced using any number of the
aspects set forth herein. In addition, the scope of the disclosure
is intended to cover such an apparatus or method which is practiced
using other structure, functionality, or structure and
functionality in addition to or other than the various aspects of
the disclosure set forth herein. It should be understood that any
aspect of the disclosure disclosed herein may be embodied by one or
more elements of a claim.
[0013] The word "exemplary" is used herein to mean "serving as an
example, instance, or illustration." Any aspect described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other aspects.
An Example Device
[0014] FIG. 1 is a block diagram of an example device 100. The
device 100 may be a battery-operated device such as a cellular
phone, a personal digital assistant (PDA), a handheld device, a
wireless modem, a laptop computer, a tablet, a personal computer,
etc. The device 100 is an example of a device that may be
configured to implement the various systems and methods described
herein.
[0015] The device 100 may include a processor 104 that controls
operation of the device 100. The processor 104 may also be referred
to as a central processing unit (CPU). Memory 106, which may
include both read-only memory (ROM) and random access memory (RAM),
provides instructions and data to the processor 104. A portion of
the memory 106 may also include non-volatile random access memory
(NVRAM). The processor 104 typically performs logical and
arithmetic operations based on program instructions stored within
the memory 106. The instructions in the memory 106 may be
executable to implement the methods described herein.
[0016] The device 100 may also include a housing 108 that may
include a transmitter 110 and a receiver 112 to allow transmission
and reception of data between the device 100 and a remote location.
The transmitter 110 and receiver 112 may be combined into a
transceiver 114. A plurality of transmit antennas 116 may be
attached to the housing 108 and electrically coupled to the
transceiver 114. The device 100 may also include (not shown)
multiple transmitters, multiple receivers, and multiple
transceivers.
[0017] The device 100 may also include a signal detector 118 that
may be used in an effort to detect and quantify the level of
signals received by the transceiver 114. The signal detector 118
may detect such signals as total energy, energy per subcarrier per
symbol, power spectral density and other signals. The device 100
may also include a digital signal processor (DSP) 120 for use in
processing signals.
[0018] The device 100 may further include a battery 122 used to
power the various components of the device 100. The device 100 may
also include a power management integrated circuit (power
management IC or PMIC) 124 for managing the power from the battery
to the various components of the device 100. The PMIC 124 may
perform a variety of functions for the device such as DC-to-DC
conversion, battery charging, power-source selection, voltage
scaling, power sequencing, etc. In certain aspects, the PMIC 124
includes a voltage regulator (e.g., a low-dropout (LDO) regulator)
as described herein.
[0019] The various components of the device 100 may be coupled
together by a bus system 126, which may include a power bus, a
control signal bus, and a status signal bus in addition to a data
bus.
Example Low-dropout (LDO) Regulator
[0020] Certain aspects of the present disclosure generally relate
to a voltage regulator (e.g., a low-dropout (LDO) regulator).
Conventional LDOs for battery-operated devices, which are generally
designed to have outputs between 2.9 V and 3.3 V, may enter into a
drop-out zone of operation when the battery voltage drops below a
certain voltage threshold (e.g., when the difference between the
input voltage and the output voltage falls below the dropout
voltage for the LDO, where the dropout voltage is the specified
minimum voltage across the LDO to maintain regulation). For
example, an LDO may enter the drop-out zone of operation when the
input voltage (e.g., battery voltage) to be regulated is close to
the target output voltage of the LDO regulator. In the drop-out
zone of operation, the quiescent current (I.sub.Q) may dramatically
increase and cause the battery to discharge quickly. Also referred
to as the ground current or supply current, the I.sub.Q is the
current drawn by the LDO in order to control its internal
circuitry, such as the pass device, for proper operation. The
I.sub.Q of the LDO accounts for the difference between the input
and output currents of the LDO. Certain aspects of the present
disclosure are directed to an LDO having a lower I.sub.Q as
compared to conventional LDO implementations. For example, the
I.sub.Q of the LDO may be reduced by simultaneously tracking the
input and output voltages and configuring the LDO into a
pass-through mode of operation prior to the LDO transitioning to
the drop-out zone of operation, as described in more detail
herein.
[0021] FIG. 2 is a schematic diagram of an example LDO regulator
200, in accordance with certain aspects of the present disclosure.
The LDO regulator 200 may have a lower I.sub.Q than conventional
LDOs, as described in more detail herein. As illustrated, the LDO
regulator 200 may be implemented with a pass device 202 coupled
between an input voltage node 204 and an output voltage node 206.
The pass device 202 may be a transistor (e.g., p-type
metal-oxide-semiconductor (PMOS) transistor, as depicted in FIG.
2). The output voltage node 206 may be coupled to a load capacitive
element 296 and a load 298, as illustrated. During a regulation
mode, the pass device 202 may be driven in a saturation region to
generate a regulated output voltage (Vout) at the output voltage
node 206 based on the input voltage (Vin) at the input voltage node
204. In certain aspects, the pass device 202 may be driven in a
linear region of operation such that the input voltage node 204 is
effectively shorted to the output voltage node 206, putting the LDO
regulator 200 into a pass-through mode of operation, as described
in more detail herein. As used herein, two nodes are considered to
be shorted if a switch (e.g., a transistor) between the nodes is in
a closed position.
[0022] The LDO regulator 200 may include an amplifier 208 used to
drive the pass device 202 to regulate the output voltage at the
output voltage node 206 based on the input voltage at the input
voltage node 204. The output 210 of the amplifier 208 may be
coupled to the gate of the pass device 202. A first input 212
(e.g., a positive input) of the amplifier 208 may be coupled to the
output voltage node 206 via a feedback path 218. A reference
voltage (labeled "VREF") may be applied to a second input 214
(e.g., a negative input) of the amplifier 208. In certain aspects,
the first input 212 may be coupled to a tap node 292 of a voltage
divider circuit 232 coupled between the output voltage node 206 and
a reference potential node 290 (e.g., electric ground), as
described in more detail herein. For example, the amplifier 208 may
be used to compare a voltage representative of the output voltage
at the output voltage node 206 (e.g., the voltage at the tap node
292) with the reference voltage (VREF).
[0023] The LDO regulator 200 includes a comparator 220 that may be
used to compare a voltage representative of an input voltage at the
input voltage node 204 with VREF. In other words, the comparator
220 may receive a voltage at a tap node 294 of a voltage divider
circuit 234 coupled between the input voltage node 204 and the
reference potential node 290 (e.g., electric ground), as
illustrated. The output 222 of the comparator 220 may be coupled to
an enable input 216 of the amplifier 208. Depending on the output
of the comparator 220, the amplifier 208 may be enabled or
disabled. For example, an inverter 270 may be coupled between the
output of the comparator 220 and the enable input 216. Thus, if the
output voltage of the comparator 220 is logic high, the amplifier
208 may be disabled via the enable input 216. As illustrated, a
first input 226 (e.g., a negative input) of the comparator 220 may
be coupled to the input voltage node 204 via a voltage-sensing path
228. A reference voltage may be applied to a second input 224
(e.g., a positive input) of the comparator 220. In certain aspects,
the second input 214 of the amplifier 208 and the second input 224
of the comparator 220 may be coupled together to the same reference
voltage node providing VREF. For other aspects, the two reference
voltages may be different.
[0024] The LDO regulator 200 also includes a pull-down device 230
coupled between the gate of the pass device 202 and the reference
potential node 290 (e.g., electric ground). The pull-down device
230 may be a transistor (e.g., an n-type metal-oxide-semiconductor
(NMOS) transistor). The output 222 of the comparator 220 is further
coupled to the gate of the pull-down device 230. Depending on the
output voltage of the comparator 220, the pull-down device 230 may
effectively short the gate of the pass device 202 to the reference
potential node 290 (e.g., electric ground). For example, if the
output voltage of the comparator 220 is logic high, the pull-down
device 230 may be driven into a linear region, and thus, the gate
of the pass device 202 is effectively shorted to the reference
potential node 290 via the pull-down device 230. When the gate of
the pass device 202 is shorted to the reference potential node 290,
the pass device 202 may be driven in the linear region of
operation, effectively shorting the input voltage node 204 to the
output voltage node 206.
[0025] Certain aspects of the present disclosure implement the LDO
regulator 200 with a pair of voltage divider circuits 232, 234, as
described herein. The voltage divider circuit 232 has a resistive
element 232a and a resistive element 232b, which are coupled
together at the tap node 292. The tap node 292 of the voltage
divider circuit 232 may be coupled to the first input 212 of the
amplifier 208. Similarly, the voltage divider circuit 234 has a
resistive element 234a and a resistive element 234b, which are
coupled together at the tap node 294. The tap node 294 of the
voltage divider circuit 234 may be coupled to the first input 226
of the comparator 220.
[0026] In certain aspects of the present disclosure, the voltage
divider ratio of the voltage divider circuit 232 may be the same as
the voltage divider ratio of the voltage divider circuit 234. For
example, the resistive element 232a and the resistive element 234a
may have the same resistance, and the resistive element 232b and
the resistive element 234b may have the same resistance. For
example, resistive elements 234a and 234b may be replicas of
resistive elements 232a and 232b, respectively, such that the
voltage divider ratio of the first voltage divider circuit 232 and
the second voltage divider circuit 234 are the same and may track
together with changes in temperature.
[0027] The LDO regulator 200 continuously tracks the input voltage
at the input voltage node 204 and the output voltage at the output
voltage node 206 to determine when the input voltage approaches the
output voltage. When the input voltage matches (or falls within a
certain small voltage above) the output voltage, the LDO regulator
200 is configured in a pass-through mode of operation, as described
herein. In certain aspects, a resistive element 236 may be coupled
between the voltage divider circuit 234 and the input voltage node
204. The resistive element 236 may add a degree of freedom by
generating a larger voltage drop between the input voltage node 204
and the tap node 294 as compared to the voltage drop between the
output voltage node 206 and the tap node 292. As such, the LDO
regulator 200 is forced into the pass-through mode when the input
voltage is equal to some threshold voltage greater than the output
voltage, the threshold voltage being set based on the extra voltage
drop provided by the resistive element 236. In certain aspects,
instead of having the resistive element 236, the resistance of the
resistive element 234b may be set higher than the resistance of the
resistive element 232b. By forcing the LDO regulator 200 into a
pass-through mode when the input voltage matches the output voltage
or when the input voltage matches some threshold voltage greater
than the output voltage, the relatively large I.sub.Q associated
with an LDO entering the drop-out zone of operation is reduced by
preventing the LDO from entering the drop-out zone of
operation.
[0028] In certain aspects of the present disclosure, the tap node
294 of the voltage divider circuit 234 may be coupled to a positive
input of the comparator 220, and a reference node providing VREF
may be coupled to the negative input of the comparator 220. In this
implementation, the inverter 270 coupled between the output 222 of
the comparator 220 and the enable input 216 may be replaced by a
short, and an inverter (not shown) may be coupled between the
output 222 of the comparator 220 and the gate of the pull-down
device 230.
[0029] FIG. 3 illustrates example operations 300 for voltage
regulation, in accordance with certain aspects of the present
disclosure. The operations 300 may be performed by a circuit, such
as the LDO regulator 200.
[0030] The operations 300 begin at block 302 with an LDO regulator
(e.g., LDO regulator 200) performing a first comparison, via a
first amplifier (e.g., via amplifier 208), of an output voltage
(Vout) with a reference voltage (VREF), and at block 304,
regulating, via a first transistor (e.g., pass device 202), an
input voltage (Vin) at an input voltage node (e.g., input voltage
node 204) to generate the output voltage at an output voltage node
(e.g., output voltage node 206) based on the first comparison. At
block 306, the LDO regulator may perform a second comparison, via a
second amplifier (e.g., comparator 220), of the input voltage with
the reference voltage, and at block 308, short, via the first
transistor, the input voltage node to the output voltage node by
controlling a second transistor (e.g., pull-down device 230) based
on the second comparison.
[0031] In certain aspects, shorting the input voltage node to the
output voltage node at block 308 may include setting a gate voltage
of the first transistor coupled between the input voltage node and
the output voltage node to a reference potential (e.g., electrical
ground). In some cases, the operations 300 may also include
disabling the first amplifier when the gate voltage of the first
transistor coupled between the input voltage node and the output
voltage node is set to the reference potential.
[0032] In certain aspects, performing the second comparison of the
input voltage with the reference voltage at block 306 entails
comparing a voltage representative of the input voltage with the
reference voltage. In certain aspects, performing the first
comparison of the output voltage with the reference voltage at
block 302 involves comparing a voltage representative of the output
voltage with the reference voltage. In some cases, the operations
300 further include disabling the first amplifier based on the
second comparison.
[0033] In other words, a voltage provided at a first input (e.g.,
first input 212) of a first amplifier (e.g., amplifier 208) may be
compared to a reference voltage provided at a second input (e.g.,
second input 214) of the first amplifier. The voltage provided at
the first input of the first amplifier may be a voltage
representative of the output voltage, as described herein. The
voltage representative of the output voltage may be provided via a
first feedback path (e.g., the first feedback path 218). Depending
on the comparison by the first amplifier (e.g., amplifier 208), an
output voltage from the first amplifier may be applied to the gate
of a pass device (e.g., pass device 202) in order to generate a
desired output voltage at the output voltage node. For example, an
output voltage from the first amplifier may drive the gate of the
pass device 202 so that a desired output voltage (e.g., 3V) is
generated based on the input voltage (e.g., 4.5V).
[0034] As described herein, a voltage provided at a first input
(e.g., first input 226) of a second amplifier (e.g., comparator
220) may be compared to a reference voltage provided at a second
input (e.g., second input 224) of the second amplifier. The
reference voltage at the second input of the second amplifier may
be the same as the reference voltage at the second input of the
first amplifier. In certain aspects, the voltage provided to the
first input of the second amplifier may be a voltage representative
of the input voltage. The voltage representative of the input
voltage may be provided via a voltage-sensing path (e.g.,
voltage-sensing path 228). Depending on the comparison by the
second amplifier, an output voltage from the second amplifier may
be applied to the gate of a pull-down device (e.g., pull-down
device 230) and to an enable input (e.g., enable input 216) of the
first amplifier, which may result in shorting of the input voltage
node to the output voltage node (e.g., by driving the pass device
202 in a saturation region of operation). For example, when the
input voltage decreases to a voltage threshold (e.g., the input
voltage matches the output voltage), the logic state of the output
voltage of the second amplifier transitions, indicating that the
LDO is transitioning into drop-out zone. For example, the output
voltage of the second amplifier may transition from logic low to
logic high and drive the gate of the pull-down device so that the
gate of the pass device 202 is pulled down to a reference potential
(e.g., electric ground). The output voltage from the second
amplifier may also disable the first amplifier via the enable input
of the first amplifier. As a result, the first amplifier is turned
off while the pass device is fully turned on, thereby shorting the
input voltage node to the output voltage node, forcing the LDO into
pass-through mode.
[0035] In the pass-through mode, the I.sub.Q may only include the
current through resistors coupled to the input voltage node (e.g.,
resistive elements 234a, 234b, and 236) and the current through the
second amplifier (e.g., comparator 220). In this way, the I.sub.Q
may be reduced to a few microamps (.mu.A) when the LDO is operating
in the pass-through mode.
[0036] The various operations of methods described above may be
performed by any suitable means capable of performing the
corresponding functions. The means may include various hardware
and/or software component(s) and/or module(s), including, but not
limited to a circuit, an application-specific integrated circuit
(ASIC), or processor. Generally, where there are operations
illustrated in figures, those operations may have corresponding
counterpart means-plus-function components with similar
numbering.
[0037] In certain aspects, means for regulating may comprise an
amplifier such as the amplifier 208 and/or a transistor, such as
the pass device 202. In certain aspects, means for shorting may
comprise an amplifier such as the comparator 220, and/or a
transistor, such as the pull-down device 230. In certain aspects,
means for performing a comparison may include an amplifier, such as
the amplifier 208 and/or comparator 220. In certain aspects, means
for setting may include an amplifier, such as comparator 220,
and/or a transistor, such as the pull-down device 230. In certain
aspects, means for disabling may include an enable input, such as
the enable input 216 of the amplifier 208, an inverter, such as the
inverter 270, and/or an amplifier, such as the comparator 220. The
amplifiers may be implemented with operational amplifiers of
different forms, including, but not limited to inverting
amplifiers, non-inverting amplifiers, voltage followers,
comparators, differential amplifiers, and summing amplifiers. The
transistors may be p-type or n-type metal-oxide-semiconductor
transistors.
[0038] As used herein, the term "determining" encompasses a wide
variety of actions. For example, "determining" may include
calculating, computing, processing, deriving, investigating,
looking up (e.g., looking up in a table, a database, or another
data structure), ascertaining, and the like. Also, "determining"
may include receiving (e.g., receiving information), accessing
(e.g., accessing data in a memory), and the like. Also,
"determining" may include resolving, selecting, choosing,
establishing, and the like.
[0039] As used herein, a phrase referring to "at least one of" a
list of items refers to any combination of those items, including
single members. As an example, "at least one of: a, b, or c" is
intended to cover: a, b, c, a-b, a-c, b-c, and a-b-c, as well as
any combination with multiples of the same element (e.g., a-a,
a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and
c-c-c or any other ordering of a, b, and c).
[0040] The various illustrative logical blocks, modules, and
circuits described in connection with the present disclosure may be
implemented or performed with discrete hardware components designed
to perform the functions described herein. The methods disclosed
herein comprise one or more steps or actions for achieving the
described method. The method steps and/or actions may be
interchanged with one another without departing from the scope of
the claims. In other words, unless a specific order of steps or
actions is specified, the order and/or use of specific steps and/or
actions may be modified without departing from the scope of the
claims.
[0041] It is to be understood that the claims are not limited to
the precise configuration and components illustrated above. Various
modifications, changes, and variations may be made in the
arrangement, operation, and details of the methods and apparatus
described above without departing from the scope of the claims.
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