Technique for limiting overshoot after dropout condition in voltage regulators - Patents.com

Abstract

The voltage regulator (100) includes an amplifier (107) having a first amplifier input (108), a second amplifier input (109), an amplifier output (110), and an amplifier supply terminal (111). A controllable current source (112) has a control terminal coupled to the amplifier output (110) and has a current output coupled to the second amplifier input (109) via a feedback path (116). A voltage dropout detector (120) includes a voltage dropout detector input (119) and a voltage dropout detector output (121). The voltage dropout detector input (119) is coupled to the current output. A current bias boost circuit (124) includes a current bias boost input (123) and a current bias boost output (125). The current bias boost input (123) is coupled to the voltage dropout detector output (121), and the current bias boost output (125) is coupled to the amplifier supply terminal (111).

Description

[Background technology]

[0001] A voltage regulator is an electrical circuit designed to receive an input voltage and convert the input voltage to deliver a substantially constant output voltage based on the input voltage. Voltage regulators are found in devices such as computer power supplies to stabilize the DC voltage used by processors and other elements. Voltage regulators may also be found in automotive electronics, industrial electronics, or other applications, typically providing a stable voltage used to power integrated circuits or other components that utilize a constant voltage. Summary of the Invention

[0002] The voltage regulator includes an amplifier having a first amplifier input, a second amplifier input, an amplifier output, and an amplifier supply terminal. A controllable current source has a control terminal coupled to the amplifier output and has a current output coupled to the second amplifier input via a feedback path. A voltage dropout detector includes a voltage dropout detector input and a voltage dropout detector output. The voltage dropout detector input is coupled to the current output. A current bias boost circuit includes a current bias boost input and a current bias boost output. The current bias boost input is coupled to the voltage dropout detector output and the current bias boost output is coupled to the amplifier supply terminal.

[0003] An electronic system includes a power supply configured to provide a power supply voltage, a load circuit configured to operate at a load voltage, and a voltage regulator disposed between the power supply and the load circuit. The load voltage is different from the power supply voltage. The voltage regulator is configured to receive an input voltage and configured to output an output voltage. The voltage regulator includes an amplifier having a first amplifier input, a second amplifier input, an amplifier output, and an amplifier supply terminal. The amplifier supply terminal is coupled to the power supply. A controllable current source transistor has a control terminal coupled to the amplifier output and has a transistor output coupled to the second amplifier input via a feedback path. The transistor output is also coupled to the load circuit. A voltage dropout detector includes a voltage dropout detector input and a voltage dropout detector output, the voltage dropout detector input being coupled to the transistor output. A current bias boost circuit includes a current bias boost input and a current bias boost output. The current bias boost input is coupled to the voltage dropout detector output, and the current bias boost output is coupled to the amplifier supply terminal.

[0004] A method is also provided in which an input supply voltage having an input voltage level is received at an amplifier. An output voltage having an output voltage level different from the input voltage level is output from the amplifier based on the input supply voltage. The method detects whether a voltage dropout condition exists by determining whether the output voltage level drops to a first particular voltage threshold or whether the output voltage level has a voltage overshoot greater than a second particular voltage threshold. A current bias boost signal is selectively provided to the amplifier based on whether a voltage dropout condition exists. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a block diagram of an electronic system including a voltage regulator according to some examples.

[0006] [Diagram 2] 2A-2C are waveform diagrams consistent with some examples of the electronic system of FIG. 1.

[0007] [Diagram 3] FIG. 1 is a block diagram of an electronic system including a voltage regulator according to some examples.

[0008] [Figure 4] FIG. 2 is a circuit diagram of a voltage regulator according to some examples.

[0009] [Diagram 5] FIG. 2 is a circuit diagram of another voltage regulator according to some examples.

[0010] [Figure 6] 1 is a flow chart in accordance with some of the methods described herein.

[0011] [Figure 7] 1 is a flow chart in accordance with some of the methods described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The drawings are not to scale.

[0013] 1 illustrates some examples of an electronic system 100. The electronic system 100 includes a power supply 102 and a load circuit 104. A voltage regulator 106 is disposed between the power supply 102 and the load circuit 104. The voltage regulator 106 has an input 103 coupled to the output of the power supply 102 and an output 105 coupled to the load circuit 104.

[0014] Voltage regulator 106 is configured to receive an input voltage Vin on input 103 and convert the input voltage to an output voltage Vout provided on output 105. For example, in some examples, power source 102 can be a battery delivering an input voltage of approximately 14 volts and load circuit 104 can be an integrated circuit operating at approximately 5 volts, and therefore voltage regulator 106 converts the 14 volt input voltage to an output voltage of 5 volts to power the integrated circuit. Of course, this example of using a 14 volt input and a 5 volt output is merely an example, and the input and output voltages can have various other values ​​depending on the implementation.

[0015] In the ideal case, the output voltage Vout remains constant in time even when there are slow or rapid changes in the input voltage Vin. However, in practical cases where the input voltage fluctuates, there are often still corresponding fluctuations in the output voltage. For example, the input voltage may fluctuate due to changes in the power source itself (e.g., if the power source is a battery, the battery voltage may decrease as the load circuit consumes power) and / or, among others, the input voltage may fluctuate due to changes in the power demand of the load circuit 104 (e.g., if the load circuit has a sudden and significant increase in power draw, the input voltage may "drop" or "drop" for a period of time in an attempt to meet such demand), and such input voltage fluctuations are passed on to the output voltage in a damped manner in some respects.

[0016] To help maintain a relatively constant output voltage over changes in input voltage, the voltage regulator 106 includes an amplifier 107, a controllable current source 112, and a feedback path 116. The amplifier 107 has a first amplifier input 108, a second amplifier input 109, an amplifier output 110, and an amplifier supply terminal 111. The amplifier supply terminal 111 corresponds to the input 103 of the voltage regulator 106. The controllable current source 112 is disposed on a current path extending between an amplifier supply terminal Vdd and a ground terminal Vss, and has a control terminal coupled to the amplifier output 110. A first resistor 113 and a second resistor 114 are disposed on the current path, such that a first point (which corresponds to the current output of the controllable current source 112) corresponds to the output 105 of the voltage regulator 106, and a second point on the current path is coupled to the second amplifier input 109 via the feedback path 116.

[0017] The amplifier 107 is configured to compare a reference voltage (Vref) on the first amplifier input 108 with a feedback voltage (Vfb) on the second amplifier input 109, and provide a control signal on the amplifier output 110 based on this comparison. The control signal increases or decreases the amount of current passing through the controllable current source 112, thereby "adjusting" the output voltage Vout on the output 105 to correspond to the reference voltage Vref, usually with some voltage offset. For example, in an example where the reference voltage Vref is initially set to 5 volts, the output voltage Vout is 7 volts and the feedback voltage Vfb is 6 volts (due to some voltage drop through the first resistor 113, which is determined by the ratio of the first resistor 113 to the second resistor 114). In this case, the feedback voltage Vfb is greater than the reference voltage Vref, and therefore the amplifier 107 can "adjust" the voltage level of the control signal to decrease the current through the controllable current source 112, thereby decreasing the output voltage Vout. If the output voltage becomes too low (causing the feedback voltage Vfb to drop below the reference voltage Vref), the amplifier 107 again "adjusts" the voltage level of the control signal to increase the current through the controllable current source 112 and correspondingly increase the output voltage Vout. The output voltage Vout is therefore continuously controlled via the feedback path 116 to provide an output voltage that ideally tracks Vref.

[0018] Some aspects of the present description recognize that even in electronic systems that utilize this feedback, under some conditions, the input voltage Vin may still exhibit a momentary, uncorrectable "drop", such as when the load circuit 104 draws a sudden, significant increase in power. This condition is referred to in some contexts as a "voltage dropout condition". Figure 2 shows an example in which the input voltage (Vin) has an initial voltage level for a time 201, then "drops" momentarily to a second voltage level at time 202 and remains low for a time 203. As shown, the output voltage Vout somewhat follows this "drop" during times 202 and 203, even though the output voltage is lower than the input voltage since this example represents a step-down voltage regulator. The voltage dropout itself can be somewhat problematic since during a voltage dropout condition, the load circuit 104 receives a lower voltage than expected. However, a potentially bigger problem is that at time 204 (just after a voltage dropout condition), when the input voltage rises to the initial voltage level, the output voltage has a large transient voltage overshoot 206. If this voltage overshoot 206 is of sufficient magnitude, it can damage devices on the load circuit 104, leading to device failure or long term reliability concerns.

[0019] 1 includes a voltage dropout detector 120 and a current bias boost circuit 124. The voltage dropout detector 120 includes a voltage dropout detector input 119 and a voltage dropout detector output 121. The voltage dropout detector input 119 is coupled to the output of the controllable current source 112. The current bias boost circuit 124 includes a current bias boost input 123 and a current bias boost output 125. The current bias boost input 123 is coupled to the voltage dropout detector output 121 and the current bias boost output 125 is coupled to the amplifier supply terminal 111.

[0020] The current bias boost circuit 124 provides a momentary current bias boost pulse ibb in response to the voltage dropout detector 120 detecting a voltage dropout condition. A voltage dropout condition is detected when the output voltage Vout drops below a certain threshold. This current bias boost pulse ibb is provided to the amplifier supply terminal 111 to mitigate a voltage overshoot at the output 105 of the voltage regulator 106 immediately following a voltage dropout condition. Figure 2 shows example curves Vout and Vout', where Vout' is an example of a voltage overshoot that would occur in the absence of a current bias boost pulse provided by the current bias boost circuit 124, and Vout shows a mitigated output voltage overshoot when the current bias boost circuit 124 provides a current bias boost pulse.

[0021] FIG. 2 provides two examples (ibb-1 and ibb-2) of current bias boost pulses that can be provided by various current bias boost circuits.

[0022] A first current bias boost pulse ibb-1 provides an increase in current at the beginning of a voltage dropout condition at time 202 and for a period of time 203. Then, after the voltage dropout condition ends at 204, the current is increased to provide a specific current pulse for a specific time 205.

[0023] In contrast, in the second current bias boost pulse ibb-2, the current remains unchanged as the base level for a time 203, during which the required corrective bias level is actively monitored and preloaded into the bias boost circuit, but not applied to the amplifier. Then, after the voltage dropout condition ends at time 204, during a sufficiently positive supply transient, an output overshoot above a certain threshold is detected, so that the preloaded bias boost is applied as long as the output remains above the certain threshold for a variable time 207. Thus, by detecting a voltage dropout condition and providing a current bias boost pulse to the amplifier supply terminal in response to a detected voltage dropout condition or an output overshoot above a certain threshold, a voltage regulator according to the present description can limit voltage overshoot, making it more reliable than other approaches.

[0024] FIG. 3 illustrates a more detailed example of an electronic system 300 including a voltage regulator 306 disposed between a power source 302 and a load circuit 304, according to some examples. Thus, features described above with respect to FIG. 1 may be consistent with some examples of the electronic system 300 of FIG. 3 (and vice versa). For example, the voltage regulator 306 may be an example of the voltage regulator 106, the amplifier 307 may be an example of the amplifier 107, the controllable current source transistor 312 may be an example of the controllable current source 112, the voltage dropout detector 320 may be an example of the voltage dropout detector 120, and the current bias boost circuit 324 may be an example of the current bias boost circuit 124. In FIG. 3, the voltage dropout detector 320 includes a comparator circuit 330 and a voltage offset circuit 332. The current bias boost circuit 324 includes a trigger circuit 334, a current injection circuit 336, and a current sink circuit 338, which are operably coupled as shown.

[0025] The controllable current source transistor 312 may be an n-channel field effect transistor (NFET), a p-channel field effect transistor (PFET), a bipolar junction transistor (BJT, e.g., NPN or PNP), an insulated gate bipolar transistor (IGBT), and / or a junction field effect transistor (JFET). The controllable current source transistor 312 may be a depletion mode device, a drain extension device, an enhancement mode device, a natural transistor, or other type of device structure transistor. Also, the controllable current source transistor 312 (as well as any and / or all portions of the voltage regulator 306) may be implemented in or on a single crystal silicon substrate, a silicon-on-insulator (SOI) substrate, a silicon carbide substrate (SiC), a gallium nitride substrate (GaN), or a gallium arsenide substrate (GaAs), among others.

[0026] Within voltage dropout detector 320, comparator circuit 330 includes a first comparator input 340, a second comparator input 342, and a comparator output corresponding to voltage dropout detector output 344. First comparator input 340 is coupled to first amplifier input 308, and second comparator input 342 is coupled to second amplifier input 309. In the illustrated example, voltage offset circuit 332 is disposed between first amplifier input 308 and first comparator input 340, although voltage offset circuit 332 could alternatively be disposed between second amplifier input 309 and second comparator input 342. Voltage offset circuit 332 could include resistors, diodes, transistors, or any other components that induce a particular voltage offset between an input of amplifier 307 and a corresponding input of comparator circuit 330.

[0027] Within the current bias boost circuit 324, a trigger circuit 334 has a trigger input coupled to the voltage dropout detector output 344 and has a trigger output. A current injection circuit 336 is coupled between the trigger circuit output and the amplifier supply terminal 311. A current sink circuit 338 is coupled between the trigger circuit output and the amplifier 307.

[0028] The current injection circuit 336 is configured to selectively inject a first amount of current into the amplifier supply terminal 311 based on a current injection signal from the trigger circuit 334. The current sink circuit 338 is configured to selectively sink a second amount of current from the amplifier 307 while the current injection circuit 336 injects the first amount of current into the amplifier supply terminal 311. The first and second amounts of current may be equal or different depending on the exact amplifier topology used. By injecting current into the amplifier supply terminal 311 and simultaneously sinking current from the amplifier, the voltage regulator 306 of FIG. 3 provides a balanced approach to limiting potentially harmful voltage overshoot following a voltage dropout condition.

[0029] The voltage dropout detector 320 of FIG. 3 can be implemented in a number of different ways. In some cases, such as described below with respect to FIG. 4 (and above with respect to current pulse ibb-1 of FIG. 2), a current boost is provided at the onset of detection of a voltage dropout condition and continues in some manner for a particular time after the voltage dropout condition ends. In such cases, the voltage dropout detector 320 may therefore be referred to as a "voltage dropout entry detector" since it detects the onset / entry of a voltage dropout condition, which can be detected when the voltage output "drops" some particular amount, and triggers a current bias boost at the onset / entry. In other cases, such as described below with respect to FIG. 5 (and above with respect to current pulse ibb-2 of FIG. 2), a corrective bias level is actively monitored and preloaded into the bias boost circuit during the onset of a dropout condition, but no additional current bias boost is initially applied to the amplifier. Then, after the voltage dropout condition has ended, if an output overshoot above a particular threshold is detected during a sufficiently positive supply transient, it causes the current bias boost circuit to apply the preloaded bias boost as long as the output remains above the particular threshold. In these other cases, therefore, voltage dropout detector 320 may be referred to as a "voltage dropout exit output overshoot detector" since it detects the exit / exit of a voltage dropout condition and triggers the current bias boost at the exit / exit.

[0030] FIG. 4 shows a more detailed circuit diagram of a voltage regulator 406 in accordance with some examples of the present description. Like numbers refer to like features, and thus amplifier 407 is an example of amplifier 307, comparator 430 is an example of comparator circuit 330, voltage dropout entrance detector 420 is an example of voltage dropout detector 320, current bias boost circuit 424 is an example of current bias boost circuit 324, and so on. Within current bias boost circuit 424, trigger circuit 434 is an example of trigger circuit 334, current injection circuit 436 is an example of current injection circuit 336, and current sink circuit 438 is an example of current sink circuit 338. In addition to the features of FIG. 3, current bias boost circuit 424 of FIG. 4 also includes preloading bias boost circuit 433. Also, in addition to the features of FIG. 3, trigger circuit 434 of FIG. 4 also includes power on reset (POR) dropout disable circuit 435, and maintain after dropout circuit 488.

[0031] The amplifier 407 includes transistors 450, 452, 454, 456, 458, 460, which are organized into an input stage 446 and an output stage 448. Thus, the input stage 446 includes a first input stage transistor 450 and a second input stage transistor 452. A first control terminal of the first input stage transistor 450 corresponds to the first amplifier input 408, and a second control terminal of the second input stage transistor 452 corresponds to the second amplifier input 409. The source terminals of the first input stage transistor 450 and the second input stage transistor 452 are coupled to each other at a common node, which corresponds to the amplifier supply terminal 411. The output stage 448 includes a first current path 462 including the first output stage transistor 454 and the second output stage transistor 456, and a second current path 464 including the third output stage transistor 458 and the fourth output stage transistor 460. The output stage 448 also includes a first branch point 461 and a second branch point 463. A first current branch 467 and a second current branch 469 branch off from the first branch point 461. The first branch point 461 corresponds to the drain terminal of the first input stage transistor 450. A third current branch 471 and a fourth current branch 473 branch off from the second branch point 463. The second branch point 463 corresponds to the drain terminal of the second input stage transistor 452. A buffer 465 includes a buffer input coupled to the first current path 462 and a buffer output corresponding to the amplifier output 410. A bias resistor is also coupled to the buffer input.

[0032] A controllable current source transistor 412 has a control terminal (e.g., a gate terminal) coupled to the amplifier output 410. A feedback path 416 couples the drain of the controllable current source transistor 412 to the second amplifier input 409. A first resistor 413 and a second resistor 414 are disposed on the current path with the controllable current source transistor 412 to enable biasing of the output 405 and the feedback path 416.

[0033] The voltage dropout ingress detector 420 includes a voltage offset circuit 432 and a comparator 430. The voltage offset circuit 432 includes a voltage divider with a third resistor and a fourth resistor arranged in series. The ratio of the third resistor to the fourth resistor is set to provide a desired voltage offset, the voltage offset being selected to prevent triggering a dropout operation during normal non-dropout amplifier operation, the value of which depends on the statistical input offset of the amplifier. For example, if x% is desired to be 50%, the resistance of the third resistor and the resistance of the fourth resistor are equal. An exemplary x% value is 4%, and the ratio of the third resistor to the fourth resistor to achieve this offset is, for example, a 1:24 upper and lower resistor ratio.

[0034] The comparator 430 includes transistors 466, 468, 470, 472, 474, 478, 480, and 482, a Schmitt trigger 476, and an inverter 484 that drives the voltage dropout detector output 444. A first comparator transistor 466 on the first current leg has a gate corresponding to the first comparator input 440, and a second comparator transistor 470 on the second current leg has a gate corresponding to the second comparator input 442. The voltage dropout detector output 444 is coupled to an input of the trigger circuit 434.

[0035] Voltage offset circuit 432, in conjunction with transistors 466, 470, 478, and 480, provides a built-in voltage offset between Vref and Vfb that is used to detect voltage dropout conditions and provide selective current injection and current sinking to amplifier 407, as described in more detail below.

[0036] During normal operation (e.g., when there is no voltage dropout condition), Vref-x% and Vfb are within a certain range of each other such that the first current leg comprising transistors 466, 478, and 480 is "on" and such left current leg (including 466, 468, 478, and 480) has a lower resistance than the right current leg (including 470 and 472). Therefore, node 459 is high, which turns transistor 472 more "on" and pulls the gate of 474 low. Because 474 is an NFET, this turns transistor 474 more off, establishing a high voltage on the input of Schmitt trigger 476. This in turn drives the output of Schmitt trigger 476 to a low voltage, which keeps transistor 480 on and keeps this bias condition balanced. As a result, inverter 484 causes voltage dropout detector output 444 to be high, and NOR gate 486 sends a low output to sustain circuit 488. Under this condition, first trigger output signal 493 is high, which turns off current injection circuit 436 (now including PFET 492). Second trigger output signal 495 is low, which turns off current sink circuit 438 (now including NFETs 494, 496). Therefore, during normal operation, first input stage transistor 450 and second input stage transistor 452 are powered by current source 499, and no additional current is injected from current injection circuit 436 or sunk from current sink circuit 438.

[0037] When a voltage dropout condition occurs, Vfb may drop below the Vref-x%-hysteresis voltage introduced by the now-on PFET 478 (and therefore Vfb is outside of the specified range for normal operation), and the second current leg including transistor 470 will be "on" more than the first current leg including transistors 466 and 468, turning transistor 472 "on" less and pulling the gate of 474 high (and therefore 474, an NFET, will be "on" more). This also pulls the input of Schmitt trigger 476 low, driving the output of Schmitt trigger 476 high (e.g., signal "dropout" is also high). This also turns off transistor 480, so that 466 and 468 now have equal resistance to 470 and 472, thereby completing the built-in voltage offset between a voltage dropout condition and normal operation. This sets up the comparator to exit the dropout state when Vfb rises above the Vref-x% threshold again. As a result, during a voltage dropout condition, the voltage dropout detector output 444 is low and the NOR gate 486 potentially sends a high output to the sustain circuit 488. Because the power-on reset (POR) dropout disable circuit 490 outputs logic 1 only during a power-on reset condition and logic 0 at other times, the NOR gate 486 sends a high output during a voltage dropout condition other than a voltage dropout condition that may occur during a power-on reset. The circuit 490 disables the trigger circuit until after the first output power-on, at which point the output of the circuit 490 is a continuous logic 0. Therefore, under such a voltage dropout condition, the first trigger output signal 493 is low, which causes the current injection circuit (here PFET 492) to turn on. The second trigger output signal 495 is high, which causes the current sinking circuitry (here, NFETs 494, 496) to also turn on.The sustain circuit 488 holds the first and second trigger output signals with these voltages for a particular time after the voltage dropout entrance detector 420 signals the end of detection of the voltage dropout condition, thereby providing current injection into the amplifier supply terminal 411 while simultaneously providing current sinking from the second 469 and fourth 473 current branches. In this manner, the voltage dropout entrance detector 420 and the current bias boost circuit 424 mitigate voltage overshoot that occurs immediately following a voltage dropout condition.

[0038] 5 is a more detailed circuit diagram of a voltage regulator 506, according to some examples of the present description. Again, like numbers refer to like features, and thus amplifier 407 is an example of amplifier 307, voltage dropout output overshoot detector 520 is an example of voltage dropout detector 320, current bias boost circuit 524 is an example of current bias boost circuit 324, etc. Within current bias boost circuit 524, trigger circuit 534 is an example of trigger circuit 334, current injection circuit 436 is an example of current injection circuit 336, and current sink circuit 438 is an example of current sink circuit 338.

[0039] Amplifier 407 includes transistors 450, 452, 454, 456, 458, 460 organized into an input stage 446 and an output stage 448, which are the same as those described above with respect to Figure 4. The controllable current source transistor 412 and feedback path 416 are also the same as those described above in Figure 4.

[0040] The voltage dropout exit output overshoot detector 520 includes a comparator with a built-in voltage offset between a first comparator input 540 and a second comparator input 542. For example, the voltage dropout exit output overshoot detector 520 includes transistors 550, 552, 554, 556, 558, 560, and 562 and a Schmitt trigger 564. The trigger circuit 534 includes an inverter 566 and provides a first trigger output signal 568 to the current injection circuit 436 and a second trigger output signal 570 to the current sink circuit 438.

[0041] 5, the built-in voltage offset between Vref and Vfb arises due to the fact that there is a first voltage drop across 550 on the first current leg, and a second voltage drop across 554 and 556 on the second current leg. For example, because transistor 550 is only a single transistor and 554 and 556 are two transistors in series with each other, 554 and 556 represent a higher resistance than 550, and a larger voltage drop occurs across 554 and 556, allowing for a built-in voltage offset.

[0042] During normal operation (e.g., when there is no voltage dropout condition), Vref and Vfb are within a certain range of each other such that transistor 550 is "on" and therefore the gate of 558 is high, which turns transistor 558 more "on" and pulls the gate of 560 low. Since 560 is an NFET, this turns transistor 560 more off and establishes a high voltage on the input of Schmitt trigger 564. This in turn drives the output of Schmitt trigger 564 to a low voltage. Therefore, under this condition, the first trigger output signal 568 is high, which turns off the current injection circuit 436 (which now includes PFET 492). The second trigger output signal 570 is low, which turns off the current sink circuit 438 (which now includes NFETs 494, 496) as well. Therefore, during normal operation, the first input stage transistor 450 and the second input stage transistor 452 are powered by the current source 499, and no additional current is injected from the current injection circuit 436 or drawn from the current sink circuit 438.

[0043] After a voltage dropout condition occurs and the supply voltage starts to rise while coming out of the dropout condition, the supply voltage usually rises fast enough to cause an overshoot at the voltage regulator output. The designed offset in the voltage dropout exit output overshoot detector 520 is set up to trigger when the FB input 542 rises above the VREF input 540 by a specific comparator offset. When the regulator output voltage overshoots beyond a specific threshold, the FB input 542 becomes greater than VREF plus a specific comparator offset, and the second comparator current leg, including transistors 554, 556, is turned "on" more than the first comparator current leg, including transistors 550, 552. Transistor 552 is turned off, which turns off transistor 558 (hence NFET 560 is more "on"). This also pulls the input of Schmitt trigger 564 low, driving the output of Schmitt trigger 564 high. Therefore, under such a voltage dropout condition, the first trigger output signal 568 is low, which turns on the current injection circuit (here PFET 492), and the second trigger output signal 570 is high, which turns on the current sink circuit (here NFETs 494, 496). Therefore, the voltage dropout outlet output overshoot detector 520 and the trigger circuit 534 bias the first trigger output signal 568 and the second trigger output signal 570 to provide current injection to the amplifier supply terminal 411 during a voltage dropout condition, while simultaneously providing current sink from the second current branch 469 and the fourth current branch 473. Such a trigger circuit turns on the transistors 494, 496, and 492 to activate the preloaded bias that was monitoring the amount of change in the dropout outlet before the overshoot condition occurred, in order to quickly apply a bias boost when needed. In this manner, the voltage dropout output overshoot detector 520 and the current bias boost circuit 524 mitigate the voltage overshoot that occurs immediately following a voltage dropout condition.

[0044] FIG. 6 is a flow chart illustrating a method in some examples.

[0045] An input supply voltage is received at an amplifier in operation 602. The input supply voltage has an input voltage level.

[0046] In operation 604, an output voltage is provided from the amplifier based on the input supply voltage, the output voltage having an output voltage level different from the input voltage level.

[0047] In operation 606, the method detects whether the input supply voltage drops by a particular voltage threshold. In some cases, this can be detected by using a built-in voltage offset included in the voltage dropout detector circuit.

[0048] In operation 608, a current bias boost signal is selectively provided to the amplifier based on whether the input supply voltage has dropped.

[0049] FIG. 7 is a flow chart illustrating another method according to some examples.

[0050] An input supply voltage is received at an amplifier in operation 702. The input supply voltage has an input voltage level.

[0051] In operation 704, an output voltage is provided from the amplifier based on the input supply voltage, the output voltage having an output voltage level different from the input voltage level.

[0052] In operation 706, the method detects whether the output supply voltage exhibits a voltage overshoot condition that exceeds a particular threshold while exiting a voltage dropout condition.

[0053] In operation 708, a current bias boost signal is selectively provided to the amplifier based on whether a voltage overshoot condition is detected.

[0054] Although such methods are illustrated and described above as a series of acts or events, the illustrated ordering of such acts or events is not limiting. For example, some acts or events may occur in different orders and / or concurrently with other acts or events apart from those illustrated and / or described herein. Also, some illustrated acts or events are optional for implementing one or more aspects or examples of the present description. Also, one or more of the acts or events illustrated herein may be performed in one or more separate acts and / or phases. In some examples, the methods described above may be implemented in a computer-readable medium using instructions stored in a memory.

[0055] In this description, the term "coupled" may encompass a connection, communication, or signal path that enables a functional relationship consistent with this description. For example, (a) in a first example, device A is directly coupled to device B if device A generates a signal to control device B to perform an action, or (b) in a second example, device A is coupled to device B via an intervening component C if the intervening component C does not substantially change the functional relationship between device A and device B, and thus device B is controlled by device A via a control signal generated by device A.

[0056] A device that is "configured to" perform a certain task or function may be configured (e.g., programmed and / or hardwired) at the time of manufacture by a manufacturer to perform that function and / or may be configurable (or reconfigurable) by a user after manufacture to perform that function and / or other additional or alternative functions. Such configuration may be through the firmware and / or software programming of the device, through the construction and / or layout of the device's hardware components and interconnections, or a combination thereof.

[0057] As used herein, the terms "terminal," "node," "interconnect," "pin," and "lead" are used interchangeably. Unless specifically stated to the contrary, such terms are used generally to mean an interconnection between or a termination of a device element, circuit element, integrated circuit, device, or other electronic or semiconductor component.

[0058] A circuit or device described herein as including certain components may instead be adapted to be coupled to such components to form the described circuit element or device. For example, a structure described as including one or more semiconductor elements (such as transistors), one or more passive elements (such as resistors, capacitors, and / or inductors), and / or one or more sources (such as voltage and / or current sources) may instead include only semiconductor elements within a single physical device (e.g., a semiconductor die and / or integrated circuit (IC) package) and may be adapted to be coupled to at least some of such passive elements and / or sources, either during or after manufacture, e.g., by an end user and / or a third party, to form the described structure.

[0059] Although the use of certain transistors is described herein, other transistors (or equivalent devices) may be substituted with little or no modification to the remaining circuit elements. For example, field effect transistors, bipolar junction transistors (BJTs, e.g., NPN or PNP), insulated gate bipolar transistors (IGBTs), and / or junction field effect transistors (JFETs) may be used in place of or in conjunction with the devices described herein. The transistors may be depletion mode devices, drain extension devices, enhancement mode devices, natural transistors, or other types of device structure transistors. Also, the devices may be implemented in / on silicon substrates (Si), silicon carbide substrates (SiC), gallium nitride substrates (GaN), or gallium arsenide substrates (GaAs).

[0060] While certain elements of the described examples are included within an integrated circuit and others are external to the integrated circuit, in other examples additional or fewer features may be incorporated within the integrated circuit. Also, some or all of the features shown as being external to the integrated circuit may be included within the integrated circuit and / or some features shown as being internal to the integrated circuit may be incorporated external to the integrated circuit. As used herein, the term "integrated circuit" refers to one or more circuits that are (i) incorporated in / on a semiconductor substrate, (ii) incorporated in a single semiconductor package, (iii) incorporated in the same module, and / or (iv) incorporated in / on the same printed circuit board.

[0061] Use of the term "ground" in the preceding description includes chassis ground, earth ground, floating ground, virtual ground, digital ground, common ground, and / or any other form of ground connection applicable or suitable to the teachings of the present description. Unless otherwise stated, "about," "approximately," or "substantially" preceding a value means + / - 10 percent of that parameter. Modifications in the described examples are possible and other implementations are possible within the scope of the claims.

Claims

1. 1. A voltage regulator comprising: an amplifier having a first amplifier input, a second amplifier input, an amplifier output, and an amplifier supply terminal; a controllable current source having a control terminal coupled to the amplifier output and a current output coupled to the second amplifier input via a feedback path; a voltage dropout detector having a voltage dropout detector input coupled to the current output and a voltage dropout detector output; a current bias boost circuit having a current bias boost input coupled to the voltage dropout detector output and a current bias boost output coupled to the amplifier supply terminal; a trigger circuit coupled to the voltage dropout detector output; a current injection circuit coupled to the trigger circuit and to the amplifier supply terminal; a current sink circuit coupled to the trigger circuit and the amplifier; the current bias boost circuit, , a voltage regulator.

2. 2. The voltage regulator of claim 1, the amplifier is configured to receive a reference voltage signal on the first amplifier input; 1. A voltage regulator having an input configured to receive a supply voltage and an output configured to provide an output voltage, the output voltage being different from the supply voltage and being substantially constant over changes in the supply voltage.

3. 2. The voltage regulator of claim 1, 10. A voltage regulator comprising: a voltage dropout detector including a comparator circuit having a first comparator input coupled to the first amplifier input, a second comparator input coupled to the second amplifier input, and a comparator output coupled to the current bias boost input.

4. 4. The voltage regulator of claim 3, the trigger circuit having a trigger input coupled to the comparator output and a trigger circuit output; the current injection circuit is coupled between the trigger circuit output and the amplifier supply terminal and configured to selectively inject a first amount of current into the amplifier supply terminal based on a current injection signal from the trigger circuit; the current sink circuit is coupled between the trigger circuit output and the amplifier and configured to selectively sink a second amount of current from the amplifier while the current injection circuit injects the first amount of current into the amplifier supply terminal.

5. 5. The voltage regulator of claim 4, 10. The voltage regulator of claim 9, wherein the current bias boost circuit further comprises a preloading bias boost circuit coupled between the current output and each of the current injecting circuit and the current sinking circuit, the preloading bias boost circuit configured to continuously monitor the current output and set current boost bias levels that induce the first amount of current and the second amount of current.

6. 5. The voltage regulator of claim 4, 1. The voltage regulator of claim 1 , wherein the current bias boost circuit further comprises a post-dropout maintain circuit configured to receive a voltage dropout signal indicating a voltage dropout condition and to maintain the boosted current bias level for a delay after the voltage dropout condition has ended.

7. 5. The voltage regulator of claim 4, The voltage regulator further includes a power-on reset dropout disable circuit configured to disable the trigger circuit until after the voltage regulator is initially powered on.

8. 2. The voltage regulator of claim 1, the amplifier is an input stage, a first input stage transistor having a control terminal corresponding to the first amplifier input and a source terminal; a second input stage transistor having a control terminal corresponding to the second amplifier input and a source terminal; the input stage including A voltage regulator wherein the source terminals of the first input stage transistor and the second input stage transistor are coupled together at a common node corresponding to the amplifier supply terminal.

9. 9. The voltage regulator of claim 8, the amplifier is an output stage, a first branch point where a first branch and a second branch branch from a drain terminal of the first input stage transistor; a second branch point where a third branch and a fourth branch branch from the drain terminal of the second input stage transistor; a buffer having a buffer input coupled to the first branch point and a buffer output coupled to the amplifier output and a control terminal of the controllable current source; a voltage regulator including the output stage,

10. 10. The voltage regulator of claim 9, 10. A voltage regulator, wherein the voltage dropout detector includes a comparator circuit having a first comparator input coupled to the first amplifier input, a second comparator input coupled to the second amplifier input, and a comparator output.

11. 11. The voltage regulator of claim 10, the trigger circuit having a trigger circuit input coupled to the comparator output and a trigger circuit output; the current injection circuit having a current injection circuit input coupled to the trigger circuit output and a current injection circuit output coupled to the common node; 1. A voltage regulator comprising: a first current-sinking transistor coupled to the trigger circuit output and either the first branch or the second branch; and a second current-sinking transistor coupled to the trigger circuit output and either the third branch or the fourth branch.

12. 2. The voltage regulator of claim 1, the current bias boost circuit providing a current bias boost pulse at a first current level in response to the voltage dropout detector detecting a voltage dropout condition; providing the current bias boost pulse at a second current level greater than the first current level when an end of the voltage dropout condition occurs. a voltage regulator configured to:

13. 13. The voltage regulator of claim 12, The voltage regulator, wherein the current bias boost circuit is further configured to apply the current bias boost pulse for a period of time after the voltage dropout condition ends.

14. 2. The voltage regulator of claim 1, 1. A voltage regulator comprising: a first input terminal for supplying a current bias boost pulse to a first output terminal of a first supply of a first voltage; a second input terminal for supplying a current bias boost pulse to a first output terminal of a first voltage;

15. 1. An electronic system comprising: a power supply configured to provide a power supply voltage; a load circuit configured to operate at a load voltage different from the power supply voltage; a voltage regulator disposed between the power supply and the load circuit and configured to receive an input voltage and provide an output voltage, an amplifier having a first amplifier input, a second amplifier input, an amplifier output, and an amplifier supply terminal coupled to the power supply; a controllable current source transistor having a control terminal coupled to the amplifier output and a transistor output coupled to the second amplifier input via a feedback path, the transistor output being coupled to the load circuit; a voltage dropout detector having a voltage dropout detector input coupled to the transistor output and a voltage dropout detector output; a current bias boost circuit having a current bias boost input coupled to the voltage dropout detector output and a current bias boost output coupled to the amplifier supply terminal; a trigger circuit coupled to the voltage dropout detector output; a current injection circuit coupled to the trigger circuit and to the amplifier supply terminal; a current sink circuit coupled to the trigger circuit and to the amplifier; the current bias boost circuit, a voltage regulator including: an electronic system,

16. 16. The electronic system of claim 15, An electronic system wherein the power source is a battery and the load circuit is an integrated circuit.

17. 1. A method comprising: receiving an input supply voltage having an input voltage level at an amplifier; providing an output voltage from the amplifier based on the input supply voltage, the output voltage having an output voltage level different from the input voltage level; Detecting whether a voltage dropout condition exists by determining whether the output voltage level drops at a first voltage threshold or whether the output voltage level has a voltage overshoot greater than a second voltage threshold; selectively providing a current bias boost signal based on whether the voltage dropout condition exists; in response to the current bias boost signal, providing a source current to the amplifier and providing a sink current from the amplifier while the source current is provided to the amplifier; A method comprising:

18. 18. The method of claim 17, The method of claim 1, wherein the source current increases to a first current level when the voltage dropout condition exists and increases to a second current level greater than the first current level when the voltage dropout condition ends.

19. 20. The method of claim 18, The method wherein the second current level is applied for a period of time after the voltage dropout condition ends.

20. 18. The method of claim 17, The method of claim 1, wherein the source current remains at the base current level while the voltage dropout condition exists and increases to a second current level greater than the base current level when the voltage dropout condition ends.

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