Low dropout regulator

Abstract

The utility model provides a low dropout linear regulator which comprises a multi-output band-gap reference source, a filtering selection circuit and an adjusting output circuit, the multi-output band-gap reference source is used for outputting multiple paths of first reference voltage, and the filtering selection circuit can trigger on-off according to a received selection control signal. And the adjusting output circuit compares the second reference voltage with the output voltage and adjusts the output voltage, so that the output voltage is controlled to be the second reference voltage constantly, and constant-voltage output is realized. According to the low dropout linear regulator, the multi-output band-gap reference source, the filtering selection circuit and the adjusting output circuit are arranged, so that multi-gear adjustable, stable and low-noise direct-current voltage can be output, a high power supply rejection ratio is achieved, and the power supply requirements of different circuit modules or application scenes are met.

Description

TECHNICAL FIELD

[0001] The utility model belongs to circuit and system technical field especially relates to a low voltage difference linear voltage regulator. BACKGROUND

[0002] The low voltage difference linear voltage regulator is an important device in power management circuit, and its function is to realize fast and accurate output voltage regulation between small voltage difference input and output voltage, so as to meet the diversified power supply demand of different functional circuit modules such as processor, sensor and radio frequency device in modern electronic equipment.

[0003] The functional circuit module in the actual application scene often needs different DC voltage power supply, if the low voltage difference linear voltage regulator can only output a DC voltage, then the required quantity is bound to be many, which will complicate the circuit design and increase the circuit manufacturing cost. UTILITY MODEL CONTENTS

[0004] The utility model discloses a low voltage difference linear voltage regulator, which aims to simultaneously realize the performance of multi-grade adjustable output voltage, low noise and high power supply rejection ratio, effectively suppress power ripple, and provide diversified, stable and low-noise power supply voltage for functional circuit modules with low voltage power supply demand.

[0005] The utility model embodiment provides a low voltage difference linear voltage regulator, comprising:

[0006] The multi-output bandgap reference source is used for outputting a plurality of first reference voltages, and the amplitudes of the first reference voltages are different.

[0007] The filter selection circuit is connected with the multi-output bandgap reference source, and the filter selection circuit is used for filtering each first reference voltage and outputting a plurality of second reference voltages, and according to the selection control signal, one second reference voltage is selected and outputted, and the amplitudes of the second reference voltages are different.

[0008] The adjustment output circuit is connected with the filter selection circuit, and is used for comparing and adjusting one second reference voltage received with the output voltage of the low voltage difference linear voltage regulator, so that the output voltage is constant and is the second reference voltage received.

[0009] Optionally, the filter selection circuit comprises:

[0010] a plurality of filter switch circuits connected with the plurality of voltage output terminals of the multi-output bandgap reference source, the filter switch circuit configured to filter a corresponding one of the first reference voltages received thereby into a second reference voltage, and to pass the corresponding second reference voltage to an output terminal thereof in response to a first switch control signal, or to block the second reference voltage from the output terminal thereof in response to a second switch control signal;

[0011] a resistance state switching circuit connected between the plurality of filter switch circuits and the regulation output circuit, the resistance state switching circuit configured to switch to a first resistance state in response to a third switch control signal to increase a transient response speed of the second reference voltage output to the regulation output circuit, and to switch to a second resistance state in response to a fourth switch control signal to perform secondary filtering of the first reference voltage to stably output the second reference voltage to the regulation output circuit.

[0012] Optionally, the filter switch circuit includes a first resistor, a first capacitor, and a first transistor.

[0013] a first end of the first resistor is connected with a corresponding one of the voltage output terminals of the multi-output bandgap reference source, a second end of the first resistor, a first end of the first transistor, and a first end of the first capacitor are connected, a second end of the first capacitor is connected to ground, a second end of the first transistor is connected with an input terminal of the resistance state switching circuit, and a control terminal of the first transistor is configured to receive the first switch control signal or the second switch control signal.

[0014] Optionally, the resistance state switching circuit includes a second resistor, a second capacitor, and a second transistor.

[0015] a first end of the second resistor and a first end of the second transistor are connected to form the input terminal of the resistance state switching circuit, a second end of the second resistor, a second end of the second transistor, a first end of the second capacitor, and an input terminal of the regulation output circuit are connected, a second end of the second capacitor is connected to ground, and a control terminal of the second transistor is configured to receive the third switch control signal or the fourth switch control signal.

[0016] Optionally, the multi-output bandgap reference source includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a first diode, a second diode, a third diode, a multi-tap resistor, and a first operational amplifier.

[0017] The first end of the third transistor, the first end of the fourth transistor, the first end of the fifth transistor and the first end of the sixth transistor are connected with a direct current bias voltage, the control end of the third transistor, the control end of the fourth transistor, the control end of the fifth transistor, the control end of the sixth transistor and the output end of the first operational amplifier are connected, the second end of the third transistor, the first end of the third resistor, the first end of the fourth resistor, the first end of the sixth resistor and the non-inverting input end of the first operational amplifier are connected, the second end of the fourth resistor and the anode of the first diode are connected, the second end of the fourth transistor, the first end of the fifth resistor, the first end of the seventh resistor, the anode of the second diode and the inverting input end of the first operational amplifier are connected, the second end of the fifth transistor, the second end of the sixth resistor, the second end of the seventh resistor and the anode of the third diode are connected, the second end of the third resistor, the cathode of the first diode, the cathode of the second diode, the cathode of the third diode and the second end of the fifth resistor are grounded, the second end of the sixth transistor is connected with the first end of the multi-tap resistor, the second end of the multi-tap resistor is grounded, and the multiple taps of the multi-tap resistor constitute multiple voltage output ends of the multi-output bandgap reference source.

[0018] Optionally, the regulating output circuit comprises:

[0019] a power transistor, an input end of the power transistor being connected with an input voltage, an output end of the power transistor constituting an output end of the regulating output circuit, the power transistor being used for regulating an output voltage of the low-dropout linear regulator according to a received error amplification signal;

[0020] a feedback circuit, the feedback circuit being connected with the output end of the power transistor, the feedback circuit being used for feeding back the output voltage of the low-dropout linear regulator;

[0021] an error amplification circuit, the error amplification circuit being connected with the filter selection circuit, the feedback circuit and the power transistor respectively, the error amplification circuit being used for comparing one of the received second reference voltages with the output voltage of the low-dropout linear regulator and outputting the error amplification signal to the power transistor, so that the output voltage is constant as the received second reference voltage;

[0022] a frequency compensation circuit, the frequency compensation circuit being connected with the output end of the error amplification circuit, the frequency compensation circuit being used for frequency compensating the error amplification signal.

[0023] Optionally, the error amplification circuit comprises a second operational amplifier.

[0024] The noninverting input end of the second operational amplifier is connected with the output end of the filter selection circuit, the inverting input end of the second operational amplifier is connected with the output end of the feedback circuit, and the output end of the second operational amplifier is connected with the control end of the power transistor.

[0025] Optionally, the frequency compensation circuit comprises a third capacitor, a fourth capacitor, a seventh transistor and an eighth transistor.

[0026] The first end of the seventh transistor is connected with a direct current bias voltage, the second end of the seventh transistor is connected with the first end of the third capacitor, the control end of the seventh transistor, the second end of the third capacitor, the second end of the fourth capacitor, the control end of the eighth transistor, the output end of the error amplification circuit and the control end of the power transistor are connected, the first end of the eighth transistor is grounded, and the second end of the eighth transistor is connected with the first end of the fourth capacitor.

[0027] Optionally, the power transistor is an NMOS transistor, and the drain, the source and the gate of the NMOS transistor constitute the input end, the output end and the control end of the power transistor respectively.

[0028] Optionally, the feedback circuit comprises a current source, the first end of the current source is connected with the output end of the power transistor, and the second end of the current source is grounded.

[0029] The low-dropout linear voltage regulator comprises a multi-output bandgap reference source, a filter selection circuit and an adjusting output circuit, the multi-output bandgap reference source is used for outputting a plurality of first reference voltages, the filter selection circuit can be triggered to be turned on and turned off according to a received selection control signal, and a corresponding first reference voltage is selected to be filtered and output as a second reference voltage, the adjusting output circuit compares the second reference voltage with an output voltage and adjusts the output voltage, so that the output voltage is controlled to be constant as the second reference voltage, constant voltage output is realized, the low-dropout linear voltage regulator can output a plurality of grades of adjustable, stable and low-noise direct currents by arranging the multi-output bandgap reference source, the filter selection circuit and the adjusting output circuit, a high power supply rejection ratio is realized, and the power supply requirements of different circuit modules or application scenarios can be met. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical scheme in the embodiments of the utility model, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the utility model, and other drawings can be obtained by those skilled in the art without creative labor under the premise of not paying the creative labor.

[0031] Figure 1 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0032] Figure 2 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure. Figure 1 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0033] Figure 3 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure. Figure 1 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0034] Figure 4 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0035] Figure 5 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0036] Figures 6(a) to 6(d) A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0037] Fig. 7(a) and Fig. 7(b) are respectively simulated noise spectrum diagrams of the low-dropout linear regulator provided by the embodiment of the present application under 200 μA and 20 mA load current.

[0038] Figure 8 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0039] Figure 9 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0040] Figure 10 A circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the present application is shown in the figure.

[0041] Fig. 11(a) and Fig. 11(b) are respectively simulated and measured four-grade output voltage curves of the low-dropout linear regulator provided by the embodiment of the present application under 200 μA and 20 mA load current with the change of the measured ambient temperature.

[0042] In the figure, various reference signs are as follows:

[0043] 10 - multiple output bandgap reference source; 20 - filter selection circuit; 30 - regulated output circuit; 21 - filter switch circuit; 22 - resistance state switching circuit; 31 - power transistor; 32 - feedback circuit; 33 - error amplifier circuit; 34 - frequency compensation circuit;

[0044] R1 - first resistor; R2 - second resistor; R3 - third resistor; R4 - fourth resistor; R5 - fifth resistor; R6 - sixth resistor; R7 - seventh resistor; R p - multiple-tap resistor;

[0045] C1 - first capacitor; C2 - second capacitor; C3 - third capacitor; C4 - fourth capacitor;

[0046] M1 - first transistor; M2 - second transistor; M3 - third transistor; M4 - fourth transistor; M5 - fifth transistor; M6 - sixth transistor; M7 - seventh transistor; M8 - eighth transistor;

[0047] U1 - first operational amplifier; U2 - second operational amplifier;

[0048] D1 - first diode; D2 - second diode; D3 - third diode;

[0049] I1 - current source;

[0050] V ref1 - first reference voltage; V ref2 - second reference voltage; V ref1_1 - first reference voltage of first path; V ref1_2 - first reference voltage of second path; V ref1_3 - first reference voltage of third path; V ref1_4 - first reference voltage of fourth path; V ref1_n - first reference voltage of nth path V ref1_n ; V out - output voltage; V DD - DC bias voltage; V in - input voltage;

[0051] S1 - first switch control signal; S2 - second switch control signal; S3 - third switch control signal; S4 - fourth switch control signal. DETAILED DESCRIPTION

[0052] In order to make the technical problems, technical schemes and beneficial effects to be solved by the utility model more clear and apparent, the utility model is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the utility model, and are not used to limit the utility model.

[0053] It should be understood that the terms "first", "second" are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "multiple" is two or more than two, unless otherwise explicitly specified.

[0054] The low-dropout linear regulator provided by the embodiment of the utility model will be described.

[0055] As shown in Figure 1 , Figure 1 The circuit structure block diagram of the low-dropout linear regulator provided by the embodiment of the utility model. In this embodiment, the low-dropout linear regulator comprises:

[0056] The multi-output bandgap reference source 10 is used for outputting multiple first reference voltages V ref1 , the amplitudes of the first reference voltages V ref1 are different;

[0057] The filter selection circuit 20 is connected with the multi-output bandgap reference source 10, the filter selection circuit 20 is used for filtering the first reference voltages V ref1 and outputting multiple second reference voltages V ref2 , and according to the selection control signal, one second reference voltage V ref2 is outputted, the amplitudes of the second reference voltages V ref2 are different;

[0058] The adjustment output circuit 30 is connected with the filter selection circuit 20, and is used for comparing and adjusting one of the received second reference voltages V ref2 with the output voltage V out of the low-dropout linear regulator, so that the output voltage V out is constant and is the received second reference voltage V ref2 .

[0059] In this embodiment, the multi-output bandgap reference source 10 is a voltage reference source, which is used for outputting multiple first reference voltages V ref1 of different amplitudes, such as the first first reference voltage V ref1_1 , the second first reference voltage V ref1_2 , the nth first reference voltage V ref1_n , etc., to achieve the purpose of multiple voltage selection output.

[0060] The filter selection circuit 20 is connected with the multi-output bandgap reference source 10, and under the control of the selection control signal, one of the first reference voltages V ref1The filtered output is then outputted, the filter selection circuit 20 comprises a plurality of voltage input terminals and a voltage output terminal, a corresponding switch channel is configured between each voltage input terminal and the voltage output terminal, and the filter selection circuit 20 can further comprise a filter unit matched with the number of switch channels, or a common filter unit is configured at the output terminals of the plurality of switch channels.

[0061] When the selection control signals are different, different switch channels are turned on and connect one of the connected voltage input terminals and the voltage output terminal, and one of the first reference voltages V ref1 is filtered and outputted to form the second reference voltage V ref2 .

[0062] In an optional embodiment, the multi-output bandgap reference source 10 outputs four first reference voltages V ref1 , and the filter selection circuit 20 comprises four voltage input terminals and a voltage output terminal, and a corresponding switch channel and a filter unit are configured between each voltage input terminal and the voltage output terminal.

[0063] When the first selection control signal is received, the first switch channel is turned on and the remaining switch channels are turned off, and the filter selection circuit 20 selects the first first reference voltage V ref1_1 from the first voltage input terminal for filtering to obtain a second reference voltage V ref2 with a corresponding amplitude and outputted to the regulation output circuit 30.

[0064] When the second selection control signal is received, the second switch channel is turned on and the remaining switch channels are turned off, and the filter selection circuit 20 selects the second first reference voltage V ref1_2 from the second voltage input terminal for filtering to obtain another second reference voltage V ref2 with a corresponding amplitude and outputted to the regulation output circuit 30.

[0065] When the third selection control signal is received, the third switch channel is turned on and the remaining switch channels are turned off, and the filter selection circuit 20 selects the third first reference voltage V ref1_3 from the third voltage input terminal for filtering to obtain another second reference voltage V ref2 with a corresponding amplitude and outputted to the regulation output circuit 30.

[0066] When the fourth selection control signal is received, the fourth switch channel is turned on and the remaining switch channels are turned off, and the filter selection circuit 20 selects the fourth first reference voltage V ref1_4 from the fourth voltage input terminal for filtering to obtain another second reference voltage V ref2 with a corresponding amplitude and outputted to the regulation output circuit 30.

[0067] Therefore, by controlling different selection control signals, the filter selection circuit 20 can achieve different first reference voltages V. ref1 The selection and filtering are performed, and a second reference voltage V with corresponding amplitude is output. ref2 .

[0068] Among them, the first reference voltage V of each path ref1 After selection and filtering, the resulting second reference voltage V ref2 The amplitude and the corresponding selected first reference voltage V ref1 The amplitudes can be equal or proportional, and the first reference voltage V has different amplitudes. ref1 After being selected, a second reference voltage V of different amplitudes is output. ref2 .

[0069] Among them, the first reference voltage V ref1 After filtering by the filter selection circuit 20, the high-frequency noise is eliminated, achieving low-noise output.

[0070] The output circuit 30 is adjusted to achieve a constant voltage output function. When a second reference voltage V corresponding to the amplitude is received... ref2 At that time, the output circuit 30 adjusts the second reference voltage V. ref2 With the output voltage V of the low dropout linear regulator out Compare and adjust to make the output voltage V out The received second reference voltage V remains constant. ref2 When the received second reference voltage V ref2 At different times, adjust the output voltage V of the output circuit 30. out The voltage changes accordingly and eventually stabilizes at the received second reference voltage V. ref2 .

[0071] The low dropout linear regulator, by setting up a multi-output bandgap reference source 10, a filter selection circuit 20, and an adjustment output circuit 30, can output a multi-level adjustable, stable, and low-noise DC voltage, achieving a high power supply rejection ratio to meet the power supply requirements of different circuit modules or application scenarios.

[0072] Among them, the multi-output bandgap reference source 10 can adopt different voltage sources, voltage sources and voltage divider resistor combination circuits, etc., and the specific structure is not limited; the filter selection circuit 20 can select the corresponding switching circuit and filter circuit, and the specific structure is not limited; the output adjustment circuit 30 can adopt voltage follower, etc., and the specific structure is not limited.

[0073] The low-dropout linear regulator provided in this embodiment includes a multi-output bandgap reference source 10, a filter selection circuit 20, and an output adjustment circuit 30. The multi-output bandgap reference source 10 is used to output multiple first reference voltages V. ref1, the filter selection circuit 20 can be triggered on or off according to the received selection control signal, and select the corresponding first reference voltage V ref1 for filtering output as the second reference voltage V ref2 , the adjustment output circuit 30 compares the second reference voltage V ref2 with the output voltage V out , and adjusts the output voltage V out , so as to control the output voltage V out constant as the second reference voltage V ref2 , so as to realize constant voltage output. The low dropout linear regulator can output multiple adjustable, stable and low noise DC voltages by setting the multiple output bandgap reference source 10, the filter selection circuit 20 and the adjustment output circuit 30, and realize high power supply rejection ratio to meet the power supply requirements of different circuit modules or application scenarios.

[0074] In an optional embodiment, as shown in Figure 2 , the circuit structure block diagram of the filter selection circuit in Figure 2 is shown. The filter selection circuit 20 includes: Figure 1

[0075] A plurality of filter switch circuits 21 are connected one by one with the plurality of voltage output terminals of the multiple output bandgap reference source 10, and the filter switch circuit 21 is used for filtering processing the respective received corresponding first reference voltage V ref1 as the second reference voltage V ref2 , and triggering conduction according to the first switch control signal S1 to pass through the output corresponding to the second reference voltage V ref2 , or triggering off according to the second switch control signal S2 to cut off the output of the second reference voltage V ref2 ;

[0076] The resistance state switching circuit 22 is connected between the plurality of filter switch circuits 21 and the adjustment output circuit 30, and the resistance state switching circuit 22 is used for triggering switching to the first resistance state according to the third switch control signal S3 to improve the transient response speed of the second reference voltage V ref2 output to the adjustment output circuit 30, and triggering switching to the second resistance state according to the fourth switch control signal S4 to perform two-stage filtering on the first reference voltage V ref1 , and stably output the second reference voltage V ref2 to the adjustment output circuit 30.

[0077] In this embodiment, the input terminal of each filter switch circuit 21 inputs a corresponding first reference voltage V ref1 ​The output terminals of the plurality of filter switch circuits 21 are connected in common and connected to the input terminal of the blocking state switching circuit 22. At the same time, only one of the filter switch circuits 21 receives the first switch control signal S1 and switches to the on state, and the other filter switch circuits 21 receive the second switch control signal S2 and trigger the off state.

[0078] The specific structures of the filter switch circuit 21 and the blocking state switching circuit 22 are not limited.

[0079] In an optional embodiment, as shown in Figure 3 , Figure 3 The circuit structure block diagram of the regulating output circuit is shown in Figure 1 . The regulating output circuit 30 comprises:

[0080] A power transistor 31, the input terminal of the power transistor 31 is connected to the input voltage V in , the output terminal of the power transistor 31 constitutes the output terminal of the regulating output circuit 30, and the power transistor 31 adjusts the output voltage V out of the low dropout linear regulator according to the error amplification signal received by the control terminal thereof.

[0081] A feedback circuit 32 connected to the output terminal of the power transistor 31, the feedback circuit 32 is used to feedback the output voltage V out of the low dropout linear regulator.

[0082] An error amplification circuit 33 connected to the filter selection circuit 20, the feedback circuit 32 and the power transistor 31 respectively, the error amplification circuit 33 is used to compare one of the received second reference voltages V ref2 with the output voltage V out of the low dropout linear regulator, and output the error amplification signal to the control terminal of the power transistor 31, so that the output voltage V out is constant as the received second reference voltage V ref2 .

[0083] A frequency compensation circuit 34 connected to the output terminal of the error amplification circuit 33, the frequency compensation circuit 34 is used to frequency compensate the error amplification signal, so as to improve the loop stability of the regulating output circuit 30.

[0084] In this embodiment, the power transistor 31, the feedback circuit 32, the error amplifier 33 and the frequency compensation circuit 34 constitute a voltage follower, i.e. a unity gain amplifier, the amplification factor is 1, through feedback regulation, the output voltage V out of the low dropout linear regulator is stabilized at the second reference voltage V ref2 .

[0085] The power transistor 31 can be an NMOS transistor, a PMOS transistor, or the like. When the power transistor 31 is an NMOS transistor operating in a saturation region, the influence of a ripple on the input voltage V in on the output voltage V out can be suppressed, and the power supply rejection ratio can be improved. The specific structures of the feedback circuit 32, the error amplifier circuit 33, and the frequency compensation circuit 34 are not limited.

[0086] As shown in Figure 4 , a circuit diagram of a low-dropout linear regulator is provided in the embodiments of the present application. Figure 4

[0087] In an optional embodiment, the filter switch circuit 21 includes a first resistor R1, a first capacitor C1, and a first transistor M1.

[0088] The first end of the first resistor R1 is connected to a corresponding voltage output end of the multi-output bandgap reference source 10. The second end of the first resistor R1, the first end of the first transistor M1, and the first end of the first capacitor C1 are connected. The second end of the first capacitor C1 is grounded. The second end of the first transistor M1 is connected to the input end of the resistance state switching circuit 22. The control end of the first transistor M1 is configured to receive the first switch control signal S1 or the second switch control signal S2.

[0089] The resistance state switching circuit 22 includes a second resistor R2, a second capacitor C2, and a second transistor M2.

[0090] The first end of the second resistor R2 and the first end of the second transistor M2 are connected, constituting the input end of the resistance state switching circuit 22. The second end of the second resistor R2, the second end of the second transistor M2, the first end of the second capacitor C2, and the input end of the regulation output circuit 30 are connected. The second end of the second capacitor C2 is grounded. The control end of the second transistor M2 is configured to receive the third switch control signal S3 or the fourth switch control signal S4.

[0091] The multi-output bandgap reference source 10 includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a third transistor M3, a fourth transistor M4, a fifth transistor M5, a sixth transistor M6, a first diode D1, a second diode D2, a third diode D3, a multi-tap resistor R p , and a first operational amplifier U1.

[0092] The first end of the third transistor M3, the first end of the fourth transistor M4, the first end of the fifth transistor M5, and the first end of the sixth transistor M6 are connected to a direct current bias voltage V DD ​The first end of the third resistor R3, the anode of the first diode D1, the cathode of the second diode D2, the cathode of the third diode D3 and the second end of the fifth resistor R5 are grounded. The second end of the sixth transistor M6 is connected with the first end of the multi-tap resistor R p The second end of the multi-tap resistor R p The second end of the multi-tap resistor R p The multiple taps of the multi-tap resistor R

[0093] The error amplification circuit 33 comprises a second operational amplifier U2.

[0094] The non-inverting input end of the second operational amplifier U2 is connected with the output end of the filter selection circuit 20. The inverting input end of the second operational amplifier U2 is connected with the output end of the feedback circuit 32. The output end of the second operational amplifier U2 is connected with the control end of the power transistor 31.

[0095] The frequency compensation circuit 34 comprises a third capacitor C3, a fourth capacitor C4, a seventh transistor M7 and an eighth transistor M8.

[0096] The first end of the seventh transistor M7 is connected with a direct current bias voltage V DD The second end of the seventh transistor M7 is connected with the first end of the third capacitor C3. The control end of the seventh transistor M7, the second end of the third capacitor C3, the second end of the fourth capacitor C4, the control end of the eighth transistor M8, the output end of the error amplification circuit 33 and the control end of the power transistor 31 are connected. The first end of the eighth transistor M8 is grounded. The second end of the eighth transistor M8 is connected with the first end of the fourth capacitor C4.

[0097] The power transistor 31 is an NMOS type transistor. The drain, the source and the gate of the NMOS type transistor respectively constitute the input end, the output end and the control end of the power transistor 31.

[0098] The feedback circuit 32 comprises a current source I1, a first end of the current source I1 being connected to the output end of the power transistor 31, and a second end of the current source I1 being grounded.

[0099] In this embodiment, the first operational amplifier U1 is used to clamp the voltage of the second end (drain) of the third transistor M3 and the fourth transistor M4, so as to ensure that the voltages of the two nodes are equal. According to the voltage-current relationship of the third resistor R3, the fourth resistor R4, the first diode D1, the second diode D2 and the fifth resistor R5, the third transistor M3 and the fourth transistor M4 generate a low-temperature coefficient current. The sixth resistor R6, the seventh resistor R7 and the third diode D3 are used to further reduce the temperature coefficient of the current. The low-temperature coefficient current is input to the multi-tap resistor R p to generate different voltage drops and form a plurality of first reference voltages V ref1 of different amplitudes. Please refer to Figure 4 , Figure 4 In this embodiment, the multi-tap resistor R p contains four taps, and each tap outputs a first reference voltage V ref1 of different amplitudes.

[0100] The first reference voltages V ref1 of different amplitudes are output to different filter switch circuits 21. The first resistor R1 and the first capacitor C1 of the filter switch circuit 21 constitute a low-pass filter unit and perform a first-order low-pass filtering on the input first reference voltage V ref1 . The first transistor M1 is triggered to turn on according to the received first switch control signal S1, and outputs the filtered voltage to the resistance state switching circuit 22, and is triggered to turn off according to the received second switch control signal S2.

[0101] The second resistor R2 and the second capacitor C2 of the resistance state switching circuit 22 constitute a low-pass filter unit and perform a second-order low-pass filtering on the first reference voltage V ref1 to eliminate high-frequency noise on the first reference voltage V ref1 . The second transistor M2 of the resistance state switching circuit 22 is used as a bypass switch. When the first reference voltage V ref1 is switched between different amplitudes, the second transistor M2 is triggered to turn on according to the received third switch control signal S3, so as to improve the transient response speed of the second reference voltage V ref2 output to the adjustment output circuit 30, and is triggered to turn off according to the fourth switch control signal S4, so as to perform a second-order filtering on the first reference voltage V ref1 and stably output the second reference voltage V ref2 to the adjustment output circuit 30.

[0102] The power transistor 31 is an NMOS transistor and works in the saturation region, which can suppress the input voltage V inThe ripple on the output voltage V out The effect of this is to improve the power supply rejection ratio.

[0103] The second operational amplifier U2 responds to the second reference voltage V input. ref2 and the output voltage V received from the output terminal (source) of power transistor 31 via feedback circuit 32 out The comparison is performed, and an error amplification signal is output to the control terminal (gate) of the power transistor 31. The power transistor 31 then adjusts the output voltage V. out To achieve the output voltage V out Closed-loop control and constant voltage output.

[0104] Meanwhile, the seventh transistor M7 and the eighth transistor M8 operate in the linear region, exhibiting variable resistance characteristics. Their resistance value is determined by the amplitude of the error amplification signal. The seventh transistor M7 and the third capacitor C3 form a series resistor-capacitor structure, generating additional zeros and poles. The eighth transistor M8 and the fourth capacitor C4 also form a series resistor-capacitor structure, generating additional zeros and poles. When the load current changes, the output voltage V... out The change in the error amplification signal output by the second operational amplifier U2 leads to a change in the resistance values ​​of the seventh transistor M7 and the eighth transistor M8, resulting in changes in the zero and pole points. This achieves dynamic frequency compensation and improves the loop stability of the regulating output circuit 30.

[0105] like Figures 5 to 8 As shown, Figure 5 The simulation loop gain and phase curves of the low dropout linear regulator provided in this embodiment of the invention under different load currents are shown. Figures 6(a) to 6(d) The Monte Carlo simulation results of the four output voltage levels of the low dropout linear regulator provided in this embodiment of the invention are shown in Figures 7(a) and 7(b). These figures show the noise spectra of the low dropout linear regulator provided in this embodiment of the invention under load currents of 200μA and 20mA, respectively. Figure 8 The power supply rejection ratio curve of the low dropout linear regulator provided in this embodiment of the present invention under a load current of 20mA.

[0106] In this embodiment, the simulated load capacitance of the low-dropout linear regulator is 300pF. To ensure phase margin, the low-dropout linear regulator uses a frequency compensation circuit 34 composed of the seventh transistor M7, the eighth transistor M8, the third capacitor C3, and the fourth capacitor C4 to widen the frequency difference between the two poles of the loop, thereby improving the phase margin. The larger the third capacitor C3 and the fourth capacitor C4, the larger the frequency difference between the poles. In this embodiment, the third capacitor C3 and the fourth capacitor C4 of the low-dropout linear regulator are 3.5pF and 9.3pF, respectively.

[0107] Depend onFigure 5 As can be seen, under load currents of 200μA (light load), 1mA (steady state), and 20mA (heavy load), the simulated phase margins of the low dropout linear regulator provided in this embodiment are 46°, 72°, and 90°, respectively, which meet the stability requirements of the circuit.

[0108] Under the above low-dropout linear regulator circuit configuration, by Figures 6(a) to 6(d) It can be seen that when the number of simulation samples for the low dropout linear regulator is 500, the four output voltages V of the low dropout linear regulator are... out The average values ​​were 811.3026mV, 860.1450mV, 909.1216mV, and 957.8044mV, respectively, and the output voltage V out The standard deviations were 10.0457mV, 10.5737mV, 11.1593mV, and 11.7430mV, respectively, and the output voltage V out The number of samples within the confidence interval (-3σ, 3σ) are 497, 497, 497, and 497, respectively, with corresponding sample proportions of 99.40%, 99.40%, 99.40%, and 99.40%. The output voltage V... out The relative deviations within the (-σ,σ) confidence intervals were 1.24%, 1.23%, 1.23%, and 1.23%, respectively.

[0109] As shown in Figures 7(a) and 7(b), under a load current of 200 μA, the simulated output noise voltage spectral density of the low dropout linear regulator is less than 5.9 nV / √Hz at 1 MHz and less than 3.4 nV / √Hz in the frequency range above 10 MHz; under a load current of 20 mA, the simulated output noise voltage spectral density of the low dropout linear regulator is less than 5.9 nV / √Hz at 1 MHz and less than 2.3 nV / √Hz in the frequency range above 10 MHz.

[0110] Depend on Figure 8 As can be seen, under a load current of 20mA, the low dropout linear regulator achieves the following output voltage V at four different levels. out The simulated power supply rejection ratios are all greater than 84dB at 1kHz and greater than 14dB at 100MHz, indicating that the low dropout linear regulator has good power supply noise suppression capability.

[0111] To experimentally verify the circuit performance of the low-dropout linear regulator provided in this embodiment, a low-dropout linear regulator chip was fabricated using a 65-nm SOI CMOS process, a test circuit board for the low-dropout linear regulator chip was fabricated using a printed circuit board process, and the bare die of the low-dropout linear regulator chip was flip-chip soldered onto the test circuit board for its circuit performance testing.

[0112] As Figure 9 , Figure 10 , Fig. 11 (a) and Fig. 11 (b) show, Figure 9 The four-grade output voltage waveforms of the low-dropout linear regulator provided by the embodiment of the utility model under simulation and measurement at room temperature (27℃) and 20mA / 200μA load current switching, Figure 10 The four-grade output voltage waveforms of the low-dropout linear regulator provided by the embodiment of the utility model under simulation and measurement at room temperature (27℃) and 200μA and 20mA load current respectively, Fig. 11 (a) and Fig. 11 (b) are the curve diagrams of the four-grade output voltage of the low-dropout linear regulator provided by the embodiment of the utility model under simulation and measurement at 200μA and 20mA load current respectively with the change of the measurement environment temperature. The low-dropout linear regulator chip test system adopts direct current power supply to power, and adopts oscilloscope to display the waveform of output voltage V out . As shown in the figure, the low-dropout linear regulator successfully outputs four-grade output voltage V out , and the simulation and measurement results of all grades of output voltage V out are in good agreement.

[0113] Among them, as shown in Figure 9 and Figure 10 , the steady-state values of the simulated four-grade output voltage V out are 810.7mV, 859.5mV, 908.3mV and 957.1mV respectively, the steady-state values of the measured four-grade output voltage V out are 816.7mV, 865.6mV, 914.6mV and 963.3mV respectively, the steady-state voltage fluctuation is within the range of ±5mV; under 200μA and 20mA two kinds of load current, the steady-state values of each grade of output voltage V out are basically unchanged, and can remain relatively stable in the process of load current switching, and the measured transient voltage overshoot / undershoot is less than 150mV.

[0114] Among them, as shown in Fig. 11 (a) and Fig. 11 (b), within the measurement environment temperature range of-40℃ to 110℃, the four-grade output voltage V out under 200μA and 20mA two kinds of load current both show good temperature stability, the maximum temperature coefficient of the simulated four-grade output voltage V out is about 35.8ppm / ℃, and the maximum deviation of the measured four-grade output voltage V out is within the range of ±3.8mV.

[0115] In the embodiments provided by the utility model, it should be understood that, first, the circuit structure of the low dropout linear regulator is only schematic and not unique, and is only one realizable circuit structure, and the circuit structure, circuit layout and transistor parameters can be optimized according to different application environments to realize a low dropout linear regulator chip with better circuit performance and smaller circuit size; second, the low dropout linear regulator can be improved based on the circuit design scheme to realize other functions. In the description of the embodiments of the utility model, the circuit structure given is the preferred structure, and referring to one of the embodiments of the utility model, the circuit structure of each part can be modified to further obtain the actual required performance.

[0116] The above-described embodiments are only used to illustrate the technical solutions of the utility model, rather than limit them. Those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced equivalently; these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and principles of the utility model, and should be included in the protection scope of the utility model.

Claims

1. A low-dropout linear regulator, characterized in that, include: A multi-output bandgap reference source is used to output multiple first reference voltages, each with a different amplitude. A filtering selection circuit is connected to the multi-output bandgap reference source. The filtering selection circuit is used to filter each of the first reference voltages and output multiple second reference voltages, and selects one of the second reference voltages to output according to the selection control signal. The amplitudes of each second reference voltage are different. An adjustment output circuit, connected to the filter selection circuit, is used to compare and adjust one of the received second reference voltages with the output voltage of the low-dropout linear regulator, so that the output voltage is constant at the received second reference voltage.

2. The low-dropout linear regulator as described in claim 1, characterized in that, The filtering selection circuit includes: Multiple filter switch circuits are connected to multiple voltage output terminals of the multi-output bandgap reference source. The filter switch circuits are used to filter the corresponding first reference voltage received by each circuit into a second reference voltage, and are triggered to turn on according to the first switch control signal to transmit the corresponding second reference voltage for output, or are triggered to turn off according to the second switch control signal to cut off the output of the second reference voltage. An impedance switching circuit is connected between the plurality of filter switching circuits and the regulating output circuit. The impedance switching circuit is used to switch to the first impedance state triggered by the third switch control signal to improve the transient response speed of the second reference voltage output to the regulating output circuit, and to switch to the second impedance state triggered by the fourth switch control signal to perform secondary filtering on the first reference voltage and output the second reference voltage to the regulating output circuit in a steady state.

3. The low-dropout linear regulator as described in claim 2, characterized in that, The filter switching circuit includes a first resistor, a first capacitor, and a first transistor; The first end of the first resistor is connected to a corresponding voltage output terminal of the multi-output bandgap reference source. The second end of the first resistor, the first end of the first transistor, and the first end of the first capacitor are connected. The second end of the first capacitor is grounded. The second end of the first transistor is connected to the input terminal of the resistance switching circuit. The control terminal of the first transistor is used to receive the first switch control signal or the second switch control signal.

4. The low-dropout linear regulator as described in claim 2, characterized in that, The resistive switching circuit includes a second resistor, a second capacitor, and a second transistor; The first end of the second resistor and the first end of the second transistor are connected to form the input terminal of the resistance switching circuit. The second end of the second resistor, the second end of the second transistor, the first end of the second capacitor, and the input terminal of the regulating output circuit are connected. The second end of the second capacitor is grounded. The control terminal of the second transistor is used to receive the third switch control signal or the fourth switch control signal.

5. The low-dropout linear regulator as described in claim 1, characterized in that, The multi-output bandgap reference source includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a first diode, a second diode, a third diode, a multi-tap resistor, and a first operational amplifier; The first terminals of the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor are connected to a DC bias voltage. The control terminals of the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor are connected to the output terminal of the first operational amplifier. The second terminal of the third transistor, the first terminal of the third resistor, the first terminal of the fourth resistor, and the first terminal of the sixth resistor are connected to the non-inverting input terminal of the first operational amplifier. The second terminal of the fourth resistor is connected to the anode of the first diode. The second terminal of the fourth transistor, the first terminal of the fifth resistor, the first terminal of the seventh resistor, and the anode of the second diode are connected to the inverting input terminal of the first operational amplifier. The second terminal of the fifth transistor, the second terminal of the sixth resistor, and the second terminal of the seventh resistor are connected to the anode of the third diode. The second terminal of the third resistor, the cathode of the first diode, the cathode of the second diode, the cathode of the third diode, and the second terminal of the fifth resistor are grounded. The second terminal of the sixth transistor is connected to the first terminal of the multi-tap resistor. The second terminal of the multi-tap resistor is grounded. The multiple taps of the multi-tap resistor constitute multiple voltage output terminals of the multi-output bandgap reference source.

6. The low-dropout linear regulator as described in any one of claims 1 to 5, characterized in that, The adjustable output circuit includes: A power transistor, wherein the input terminal of the power transistor is connected to the input voltage, and the output terminal of the power transistor constitutes the output terminal of the regulating output circuit, and the power transistor is used to adjust the output voltage of the low dropout linear regulator according to the received error amplification signal; A feedback circuit is connected to the output terminal of the power transistor, and the feedback circuit is used to provide feedback on the output voltage of the low dropout linear regulator. An error amplifier circuit is connected to the filter selection circuit, the feedback circuit, and the power transistor, respectively. The error amplifier circuit is used to compare one of the received second reference voltages with the output voltage of the low dropout linear regulator, and output the error amplification signal to the power transistor so that the output voltage is constant at the received second reference voltage. A frequency compensation circuit is connected to the output terminal of the error amplifier circuit. The frequency compensation circuit is used to perform frequency compensation on the error amplifier signal.

7. The low-dropout linear regulator as described in claim 6, characterized in that, The error amplifier circuit includes a second operational amplifier; The non-inverting input of the second operational amplifier is connected to the output of the filter selection circuit, the inverting input of the second operational amplifier is connected to the output of the feedback circuit, and the output of the second operational amplifier is connected to the control terminal of the power transistor.

8. The low-dropout linear regulator as described in claim 6, characterized in that, The frequency compensation circuit includes a third capacitor, a fourth capacitor, a seventh transistor, and an eighth transistor. The first terminal of the seventh transistor is connected to a DC bias voltage, the second terminal of the seventh transistor is connected to the first terminal of the third capacitor, the control terminal of the seventh transistor, the second terminal of the third capacitor, the second terminal of the fourth capacitor, the control terminal of the eighth transistor, the output terminal of the error amplifier circuit, and the control terminal of the power transistor are connected, the first terminal of the eighth transistor is grounded, and the second terminal of the eighth transistor is connected to the first terminal of the fourth capacitor.

9. The low-dropout linear regulator as described in claim 6, characterized in that, The power transistor is an NMOS transistor, and the drain, source, and gate of the NMOS transistor constitute the input terminal, output terminal, and control terminal of the power transistor, respectively.

10. The low-dropout linear regulator as described in claim 6, characterized in that, The feedback circuit includes a current source, the first end of which is connected to the output terminal of the power transistor, and the second end of which is grounded.

Images