CN114222232A

CN114222232A - MEMS system and signal processing circuit

Info

Publication number: CN114222232A
Application number: CN202111676181.6A
Authority: CN
Inventors: 周延青; 潘华兵; 郑泉智; 胡铁刚
Original assignee: Hangzhou Silan Microelectronics Co Ltd
Current assignee: Hangzhou Silan Microelectronics Co Ltd
Priority date: 2021-12-31
Filing date: 2021-12-31
Publication date: 2022-03-22
Anticipated expiration: 2041-12-31
Also published as: CN114222232B

Abstract

The invention provides an MEMS (micro-electromechanical systems) system and a signal processing circuit.A capacitance variation is generated by an MEMS capacitor of a capacitance MEMS sensing module under the excitation of an external sound signal, the capacitance MEMS sensing module is connected with a bias voltage generating module to access bias voltage, and a first voltage signal representing the sound signal is output according to the capacitance variation and the bias voltage; the buffer module is used for accessing the first voltage signal and carrying out impedance conversion, and outputting a second voltage signal; and the gain adjusting module is used for accessing the second voltage signal, performing gain adjustment on the second voltage signal and feeding back the second voltage signal to the capacitive MEMS sensing module. The invention can realize the positive and negative gain adjustment of the sensitivity of the capacitive MEMS sensing module through the gain adjustment module, thereby expanding the application scene of the MEMS system; meanwhile, the loss of the signal-to-noise ratio in the sensitivity adjusting process can be greatly reduced by controlling the equivalent input noise of the gain adjusting module and the buffer module, and the signal-to-noise ratio of the system is kept fixed in the gain adjusting process.

Description

MEMS system and signal processing circuit

Technical Field

The invention relates to the technical field of microphones, in particular to an MEMS system and a signal processing circuit.

Background

A capacitive MEMS microphone is a MEMS (Micro-Electro-Mechanical System) device manufactured by using a Micro-machining process. The capacitive MEMS microphone has the advantages of small volume, high sensitivity and good compatibility with the existing semiconductor technology, so that the capacitive MEMS microphone is more and more widely applied to mobile terminals such as mobile phones.

The structure of the capacitive MEMS microphone is provided with a vibrating membrane, a back plate electrode and a supporting wall body, the supporting wall body is enclosed to form a cavity, the back plate electrode is located on the supporting wall body and covers the cavity, the vibrating membrane is suspended in the cavity, and the edge of the vibrating membrane extends into the supporting wall body to be fixed. When the vibrating membrane is excited by an external sound signal, the distance between the vibrating membrane and the back plate electrode is changed, the capacitance is changed, and the capacitance change is converted into the change of a voltage signal through the integrated circuit chip and is output.

At present, a vibrating membrane and a back plate electrode can be manufactured together, the distance is less than 1.5um, the performance of a capacitive MEMS microphone is greatly improved, an MEMS microphone device with a higher signal-to-noise ratio level can be manufactured along with the improvement of the sensitivity of the capacitive MEMS microphone, however, after the preparation of the capacitive MEMS microphone is completed, the sensitivity cannot be adjusted, and when the sensitivity exceeds the specification, the use of a low-sensitivity scene is limited.

Disclosure of Invention

The invention aims to provide an MEMS system and a signal processing circuit, which can adjust the gain of a capacitance type MEMS microphone.

In order to achieve the above object, the present invention provides a MEMS system comprising:

the bias voltage generating module is used for generating bias voltage;

the capacitive MEMS sensing module comprises an MEMS capacitor, the MEMS capacitor generates capacitance variation under the excitation of an external sound signal, the capacitive MEMS sensing module is connected with the bias voltage generating module to access the bias voltage and output a first voltage signal representing the sound signal according to the capacitance variation and the bias voltage, and the first voltage signal is output through an output end;

the buffer module is connected with the output end of the capacitive MEMS sensing module so as to access the first voltage signal, perform impedance conversion and output a second voltage signal;

and the gain adjusting module is connected with the output end of the buffer module so as to access the second voltage signal, and feeds the second voltage signal back to the output end of the bias voltage generating module through the second coupling module after performing gain adjustment on the second voltage signal.

Optionally, the output end of the bias voltage generation module and the output end of the capacitive MEMS sensing module are both in a high impedance state.

Optionally, the number of the MEMS capacitors is one, and the bias voltage generation module outputs one bias voltage through one output terminal.

Optionally, the number of the MEMS capacitors is two, and the two MEMS capacitors generate reverse capacitance variation under excitation of the sound signal.

Optionally, the bias voltage generating module outputs one bias voltage through one output terminal.

Optionally, the method further includes:

and one end of the first high-resistance module is connected to a node between the output end of the capacitive MEMS sensing module and the buffer module, and the other end of the first high-resistance module is connected to a first common mode voltage.

Optionally, the bias voltage generation module outputs one bias voltage through two output ends, the capacitive MEMS sensing module further accesses a second common mode voltage, and the capacitive MEMS sensing module outputs the first voltage signal according to the capacitance variation, the two bias voltages, and the second common mode voltage.

Optionally, the method further includes:

and one end of the second high-resistance module is connected with the capacitive MEMS sensing module, and the other end of the second high-resistance module is connected with the second common-mode voltage.

Optionally, a first coupling module is connected between the output end of the capacitive MEMS sensing module and the input end of the buffer module.

Optionally, the second coupling module includes:

and the first end of the coupling capacitor is connected with the output end of the gain adjusting module, and the second end of the coupling capacitor is connected with the output end of the bias voltage generating module.

Optionally, the second coupling module further includes:

and the first end of the adjusting capacitor is connected with the second end of the coupling capacitor, and the second end of the adjusting capacitor is connected with a third common-mode voltage.

Optionally, the bias voltage generating module includes:

a charge pump module for outputting a base bias voltage; and the number of the first and second groups,

and the third high-resistance module is connected with the charge pump module so as to access the basic bias voltage and convert the basic bias voltage into the bias voltage.

Optionally, the MEMS system outputs the second voltage signal.

Optionally, the method further includes:

and the single-conversion double-module is connected with the output end of the buffer module so as to access the second voltage signal and convert the second voltage signal into a differential signal, and the MEMS system outputs the differential signal.

Optionally, the gain factor of the gain adjustment module is negative.

Optionally, a gain coefficient of the gain adjustment module is-1, the second voltage signal output by the buffer module and the signal output by the gain adjustment module form a differential signal, and the MEMS system outputs the differential signal.

Optionally, the gain factor of the gain adjustment module is positive.

Optionally, the system further comprises a digital processing module, wherein the digital processing module comprises:

the analog-digital sampling unit is used for sampling the output signal of the MEMS system to obtain a digital sampling signal;

and the digital logic unit is connected with the analog-digital sampling unit and used for carrying out format conversion on the digital sampling signal to obtain a digital voltage signal, and the MEMS system outputs the digital voltage signal.

Optionally, the digital logic unit further outputs a digital control signal under the driving of an external clock signal and an external first enable signal, and the digital control signal is used for implementing digital control of the whole MEMS system.

Optionally, the method further includes:

and the digital control module is used for outputting a digital control signal under the driving of a clock signal and an external second enabling signal, and the digital control signal is used for realizing the digital control of the whole MEMS system.

Optionally, the method further includes:

and the LDO module is used for receiving external power voltage, generating constant power voltage according to the external power voltage and supplying power to the buffer module and the gain adjustment module.

Optionally, the bias voltage generation module, the buffer module and the gain adjustment module are integrated on the same ASIC chip, and the ASIC chip is connected to the capacitive MEMS sensing module by wire bonding.

Optionally, the method further includes:

and the ESD module is connected with the ASIC chip and is used for carrying out ESD protection on the ASIC chip and the capacitive MEMS sensing module.

Optionally, the capacitive MEMS sensing module includes a capacitive MEMS microphone, a capacitive MEMS acoustic transducer, or a capacitive MEMS microphone.

Optionally, the present invention further provides a signal processing circuit, including:

the bias voltage generating module is used for generating and outputting bias voltage, the bias voltage generating module provides the bias voltage for the capacitive MEMS sensor module, and the capacitive MEMS sensor module generates a first voltage signal;

the buffer module is used for accessing the first voltage signal, performing impedance conversion and outputting a second voltage signal;

and the gain adjusting module is connected with the output end of the buffer module, is accessed to the second voltage signal, and feeds the second voltage signal back to the output end of the bias voltage generating module through the second coupling module after performing gain adjustment on the second voltage signal.

In the MEMS system and the signal processing circuit provided by the invention, the MEMS capacitor of the capacitive MEMS sensing module generates capacitance variation under the excitation of an external sound signal, the capacitive MEMS sensing module is connected with the bias voltage generating module to access the bias voltage, and outputs a first voltage signal representing the sound signal according to the capacitance variation and the bias voltage; accessing the first voltage signal by using a buffer module, performing impedance conversion and outputting a second voltage signal; and accessing the second voltage signal by using a gain adjusting module, performing gain adjustment on the second voltage signal, and feeding back the second voltage signal to the capacitive MEMS sensing module. According to the invention, the positive and negative gain adjustment of the sensitivity of the capacitive MEMS sensing module can be realized through the gain adjustment module, so that the application scene of the MEMS system is enlarged; meanwhile, the loss of the signal-to-noise ratio in the sensitivity adjusting process can be greatly reduced by controlling the equivalent input noise of the gain adjusting module and the buffering module, and the signal-to-noise ratio of the system is kept fixed in the gain adjusting process.

Drawings

FIG. 1 is a block diagram of a MEMS system according to an embodiment of the present invention;

fig. 2 is a circuit diagram of a third high impedance module according to an embodiment of the invention;

FIG. 3 is a circuit diagram of a fast boot circuit according to an embodiment of the present invention;

FIG. 4 is a circuit diagram of a simplified block diagram of the MEMS system of FIG. 1;

FIG. 5 is a block diagram of a MEMS system according to a second embodiment of the present invention;

FIG. 6 is a block diagram of a MEMS system according to a third embodiment of the present invention;

FIGS. 7a, 7b and 7c are block diagrams of three MEMS systems according to a fourth embodiment of the present invention;

FIGS. 8a, 8b and 8c are block diagrams of three MEMS systems according to a fifth embodiment of the present invention;

FIGS. 9a, 9b and 9c are block diagrams of three MEMS systems according to a sixth embodiment of the present invention;

FIGS. 10a, 10b and 10c are block diagrams of three MEMS systems according to a seventh embodiment of the present invention;

wherein the reference numerals are:

10-a bias voltage generation module; 11. 111, 112-third high impedance module; 12-a charge pump module; 13-a suction detection module; 20-capacitive MEMS sensing module; 31-a buffer module; 32-a gain adjustment module; 33-a first high impedance module; 34-a second high impedance module; 35-single-turn double module; 40-a clock signal generation module; 50-LDO module; 60-a digital control module; 70-an ESD module; 801-a third unidirectional conducting unit; 802-fast start-up circuit; 90-a digital processing module; 91-an analog digital sampling unit; 92-a digital logic cell;

clk-clock signal; CLK' -an external clock signal; vcp, Vcp01, Vcp 02-bias voltages; vin-a first voltage signal; vcp1, Vcp11, Vcp 12-base bias voltages; vs — a second voltage signal; vf-third voltage signal; output signals of Vout, Voutm, Voutp, Voutb, Voutn, Dout, Doutm, Doutp, Doutb, Doutn-MEMS systems; gain ctrl-digital control signal; vcom 1-first common mode voltage; vcom2 — second common mode voltage; vcom3 — third common mode voltage; v1 — third high impedance node; v2-third low impedance node; vdd — constant supply voltage; VDD-external supply voltage; din-an external second enable signal; lr-an external first enable signal; gnd-ground; a K-node; c1, C3-coupling resistance; c2-adjusting resistance.

Detailed Description

The following describes in more detail embodiments of the present invention with reference to the schematic drawings. The advantages and features of the present invention will become more apparent from the following description. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

Example one

Fig. 1 is a block diagram of a MEMS system provided in this embodiment. As shown in fig. 1, the MEMS system includes:

a bias voltage generating module 10 for generating a bias voltage Vcp;

the capacitive MEMS sensing module 20 includes an MEMS capacitor, where the MEMS capacitor generates a capacitance variation under the excitation of an external sound signal, the capacitive MEMS sensing module 20 is connected to the bias voltage generating module 10 to access the bias voltage Vcp, and outputs a first voltage signal Vin representing the sound signal according to the capacitance variation and the bias voltage Vcp, and the first voltage signal Vin is output through an output end;

the buffer module 31 is connected to the output end of the capacitive MEMS sensing module 20 to access the first voltage signal Vin, perform impedance conversion, and output a second voltage signal Vs;

and a gain adjusting module 32, connected to the output end of the buffer module 31 and the capacitive MEMS sensing module 20, for accessing the second voltage signal Vs, performing gain adjustment on the second voltage signal Vs, and feeding back the gain-adjusted second voltage signal Vs to the output end of the bias voltage generating module 10 through a second coupling module.

Specifically, in this embodiment, the capacitive MEMS sensing module 20 includes a MEMS capacitor, and an input end of the MEMS capacitor is connected to the bias voltage generating module 10 and is used for accessing the bias voltage Vcp; the output end of the MEMS capacitor serves as the output end of the capacitive MEMS sensing module 20, and the MEMS capacitor outputs a first voltage signal Vin representing the sound signal according to the capacitance variation and the bias voltage Vcp.

In this embodiment, the capacitive MEMS sensing module 20 is a capacitive MEMS microphone. However, it should be understood that the capacitive MEMS sensing module 20 in the present invention is not limited to a capacitive MEMS microphone, but may also be a capacitive MEMS acoustic transducer or a capacitive MEMS microphone, etc., and will not be explained one by one here.

Further, the MEMS system further includes a first high impedance module 33, one end of the first high impedance module 33 is connected to a node K between the output end of the capacitive MEMS sensing module 20 and the buffer module 31, and the other end of the first high impedance module 33 is used for accessing a first common mode voltage Vcom1, so as to provide the first common mode voltage Vcom1 to the node K and establish a static operating point for the output end of the capacitive MEMS sensing module 20.

Referring to fig. 1, the output end of the capacitive MEMS sensing module 20 is in a high impedance state, and the output first voltage signal Vin has no driving capability. For subsequent processing, an input end of the buffer module 31 is connected to an output end of the capacitive MEMS sensing module 20, and is configured to access the first voltage signal Vin and perform impedance conversion (converting from a high impedance state to a low impedance state) to output a second voltage signal Vs, so as to enhance driving capability. In this embodiment, the second voltage signal Vs output by the buffer module 31 is also used as the output signal Vout of the MEMS system.

Further, the gain adjusting module 32 is connected to the output end of the buffer module 31, and is configured to access the second voltage signal Vs and perform gain adjustment on the second voltage signal Vs. For convenience of description, the signal output by the gain adjustment module 32 is referred to as a third voltage signal Vf, that is, the third voltage signal Vf is the second voltage signal Vs with the gain adjusted.

It should be understood that the gain adjustment module 32 may be an existing circuit with gain adjustment, and will not be described in detail herein.

With continued reference to fig. 1, the second coupling module is configured to couple the third voltage signal Vf to the output end of the bias voltage generating module 10, so as to couple the third voltage signal Vf to the capacitive MEMS sensing module 20, that is, couple the third voltage signal Vf to the input end of the MEMS capacitor. The gain adjusting module 32 and the second coupling module form a feedback loop, and when a feedback coefficient on the feedback loop is a positive value, the feedback loop is a positive feedback, so that positive gain adjustment of the sensitivity of the capacitive MEMS sensing module 20 can be realized; on the contrary, when the feedback coefficient on the feedback loop is a negative value, the feedback loop is a negative feedback, and the negative gain adjustment of the sensitivity of the capacitive MEMS sensing module 20 can be realized. As can be seen, in this embodiment, the gain adjustment module 32 and the second coupling module can be used to adjust the positive and negative gains of the sensitivity of the capacitive MEMS sensing module 20, so as to expand the application scenarios of the MEMS system.

In this embodiment, the second coupling module includes a coupling capacitor C1. A first end of the coupling capacitor C1 is connected to the output end of the gain adjustment module 32 for accessing the third voltage signal Vf, and a second end of the coupling capacitor C1 is connected to the output end of the bias voltage generation module 10 for coupling the third voltage signal Vf to the capacitive MEMS sensing module 20.

Further, the second coupling module further includes a regulating capacitor C2, a first terminal of the regulating capacitor C2 is connected to a second terminal of the coupling capacitor C1, and a second terminal of the regulating capacitor C2 is connected to a third common mode voltage Vcom 3.

The coupling capacitor C1 and the adjusting capacitor C2 may be capacitors with adjustable capacitance values, so that the sensitivity of the capacitive MEMS sensing module 20 can be adjusted by adjusting the capacitance values of the coupling capacitor C1 and/or the adjusting capacitor C2. Of course, the coupling capacitor C1 and the adjusting capacitor C2 may be both capacitors with fixed capacitance values, so that the sensitivity of the capacitive MEMS sensing module 20 may also be adjusted by adjusting the gain factor of the gain adjusting module 32. Further, the coupling capacitor C1 and the adjusting capacitor C2 may be capacitors with adjustable capacitance values, and the other is a capacitor with a fixed capacitance value, which is not illustrated herein.

As an alternative embodiment, the adjusting capacitor C2 may be omitted because the gain adjusting module 32 may also adjust the amplitude of the output signal, and thus the sensitivity of the capacitive MEMS sensing module 20.

With continued reference to fig. 1, the MEMS system further includes the clock signal generating module 40, the clock signal generating module 40 provides a clock signal Clk for the whole MEMS system, and the specific connection manner of the clock signal generating module 40 will be described below.

The bias voltage generating module 10 is configured to provide the bias voltage Vcp for the capacitive MEMS sensing module 20, and an output end of the bias voltage generating module 10 is in a high impedance state.

Specifically, the bias voltage generation module 10 includes a charge pump module 12 and a third high resistance module 11. The input end of the charge pump module 12 is connected to the output end of the clock signal generating module 40, and is configured to receive the clock signal Clk and output a basic bias voltage Vcp1 under the driving of the clock signal Clk, and the third high-impedance module 11 is connected to the charge pump module 12, and is configured to access the basic bias voltage Vcp1 and stabilize the basic bias voltage Vcp1 at a high impedance state for outputting, so that the output end of the bias voltage generating module 10 is in a high impedance state.

It should be understood that the higher the bias voltage Vcp is, the better theoretically, but considering the process withstand voltage, the bias voltage Vcp is usually 4V-15V, but should not be limited thereto.

Further, the capacitive MEMS sensing module 20 may generate an actuation phenomenon (the diaphragm of the MEMS capacitor is adhered to the back plate electrode) under the excitation of an excessive sound signal, when the capacitive MEMS sensing module 20 generates the actuation phenomenon, a MEMS capacitor jumps (the MEMS capacitor suddenly increases), and meanwhile, a leakage current of the back plate electrode of the MEMS capacitor increases, so that the first voltage signal Vin output by the capacitive MEMS sensing module 20 jumps and is maintained for a period of time, thereby greatly reducing the sensitivity of the system.

Based on this, in this embodiment, the bias voltage generating module 10 further includes a pull-in detecting module 13, and an input end of the pull-in detecting module 13 may be connected to a voltage signal (hereinafter referred to as an internal signal) representing a sound signal. When the MEMS capacitor generates the pull-in phenomenon, the internal signal jumps, the pull-in detection module 13 pulls down the bias voltage Vcp when the internal signal jumps, so as to reduce the voltage value of the bias voltage Vcp (for example, the bias voltage Vcp can be pulled down to Vss, so as to ground the bias voltage Vcp Vss), release the electric charge on the back plate electrode of the MEMS capacitor, lose the effect of the electric field force, the diaphragm of the MEMS capacitor can rebound under the elastic action of the diaphragm, and the pull-in state is released, so that the sensitivity of the system can be quickly recovered.

It should be understood that the internal signal may be any voltage signal capable of representing the sound signal, such as the first voltage signal Vin, the second voltage signal Vs, or the third voltage signal Vf, for example, and the invention is not limited thereto. In this embodiment, an input end of the pull-in detection module 13 is connected to an output end of the buffer module 31, and is configured to access the second voltage signal Vs, where the second voltage signal Vs serves as the internal signal.

In this embodiment, the first high impedance module 33 and the third high impedance module 11 have the same structure, and it should be understood that the first high impedance module 33 and the third high impedance module 11 may have different structures. Next, the structure of the first high impedance module 33 and the third high impedance module 11 will be described in detail below by taking the third high impedance module 11 as an example.

Fig. 2 is a circuit diagram of the third high impedance module 11 provided in this embodiment. As shown in fig. 1 and fig. 2, the third high-resistance module 11 includes a third high-resistance node and a third low-resistance node, and one or at least two third unidirectional conducting units 801 connected in series are provided between the third high-resistance node and the third low-resistance node. In fig. 2, each of the third unidirectional conducting units 801 is a diode, the anodes and the cathodes of the diodes are sequentially connected, the anode of the first diode is used as the third low-resistance node V1, the cathode of the last diode is used as the third high-resistance node V2, the third high-resistance module 11 is conducted along the direction from the third low-resistance node V1 to the third high-resistance node V2, and is cut off along the direction from the third high-resistance node V2 to the third low-resistance node V1. The third low-resistance node V1 is connected to the charge pump module 12 for accessing the basic bias voltage Vcp1, and the third high-resistance node V2 is connected to the capacitive MEMS sensing module 20 for providing the bias voltage Vcp in a high-resistance state to the capacitive MEMS sensing module 20. The third high-resistance module 11 can utilize the diode-like I-V characteristic to have the high-resistance characteristic within a certain voltage range, so that the output end of the bias voltage generating module 10 can be stabilized in a high-resistance state, and the normal operation of the circuit is ensured.

Fig. 3 is a circuit diagram of the fast start circuit provided in this embodiment. As shown in FIG. 3, a fast start circuit 802 may be further connected between the third high impedance node V2 and the third low impedance node V1. When the voltages of the third low-resistance node V1 and the third high-resistance node V2 are close to each other, the voltage at the third high-resistance node V2 is established very slowly, the fast start circuit 802 in this embodiment is equivalent to a switch, and when the fast start circuit 802 is turned on, the third low-resistance node V1 can charge and discharge the third high-resistance node V2 quickly, so that the establishment of the voltage at the third high-resistance node V2 is accelerated, the fast start of the circuit is realized, and the start speed of the system is increased.

It should be understood that the third unidirectional conducting unit 801 in this embodiment is not limited to a diode, and may also be two MOS transistors connected in a diode connection manner.

Similarly, the first high impedance module 33 may also include a first high impedance node and a first low impedance node, where one or at least two first unidirectional conductive units are connected in series between the first high impedance node and the first low impedance node, the first low impedance node is connected to the first common mode voltage Vcom1, and the first high impedance node is connected to the node K. The first high-resistance module 33 can utilize the characteristic similar to the diode I-V characteristic to have the high-resistance characteristic within a certain voltage range, so that the output end of the capacitive MEMS sensing module 20 can be stabilized in a high-resistance state, and the normal operation of the circuit is ensured.

As an optional embodiment, a fast start circuit may also be connected between the first high-resistance node and the first low-resistance node, so as to accelerate the establishment of the voltage on the first high-resistance node and improve the start speed of the system.

In this embodiment, the first common mode voltage Vcom1 and the third common mode voltage Vcom3 are 0V-1V, but should not be limited thereto.

Referring to fig. 1, in the present embodiment, the MEMS system further includes an LDO module 50, and the LDO module 50 may receive an external power voltage VDD and accordingly provide a constant power voltage VDD for the buffer module 31 and/or the gain adjustment module 32, thereby improving the operation performance of the MEMS system.

Further, in this embodiment, the MEMS system further includes a digital control module 60, and an input end of the digital control module 60 is connected to the clock signal generating module 40, and is configured to access the clock signal Clk and output a digital control signal GainCtrl under driving of the clock signal Clk and an external second enable signal Din. The digital control signal GainCtrl is used to implement digital control of the whole MEMS system, for example, the digital control signal GainCtrl may be used for dynamic gain adjustment compensation of the gain adjustment module 32 or control of a special test mode; meanwhile, the digital control signal GainCtrl can also complete the functions of digital communication between the MEMS system and the outside, EFUSE programming control, digital signal filtering, transcoding output and the like.

It should be understood that, in this embodiment, the bias voltage generation module 10, the buffer module 31, the gain adjustment module 32, the first high impedance module 33, the clock signal generation module 40, the LDO module 50, and the digital control module 60 may be integrated on the same ASIC chip. The ASIC chip is electrically connected to the capacitive MEMS sensing module 20 by wire bonding, so as to achieve signal intercommunication.

Further, the MEMS system further includes an ESD module 70, and the ESD module 70 is connected to the ASIC chip and is configured to perform ESD protection on the ASIC chip and the capacitive MEMS sensing module. Specifically, the ESD module 70 is located near a pad of the ASIC chip, the output signal Vout of the MEMS system can be output through the ESD module 70, and a signal input from outside of the MEMS system (for example, an external second enable signal Din or an external power supply voltage VDD) can be input into the MEMS system through the ESD module 70, so as to improve the ESD performance of the MEMS system.

Further, in this embodiment, by controlling the equivalent input noise of the gain adjustment module 32 and the buffer module 31, the signal-to-noise ratio loss during the sensitivity adjustment process can be greatly reduced, and the signal-to-noise ratio of the system is kept constant during the gain adjustment process.

Specifically, FIG. 4 is a simplified block diagram of the MEMS system of FIG. 1. As shown in fig. 4, let the preset gain coefficient of the gain adjusting module 32 be k1, the gain coefficient after the gain adjusting module 32, the coupling capacitor C1 and the adjusting capacitor C2 complete gain adjustment be k2, the equivalent input noise of the buffer module 31 is vn1, the equivalent input noise of the gain adjusting module 32 is vn2, the static capacitance of the MEMS capacitor is C0, the parasitic capacitance is Cp, and the sound signal (inpersure) causes a capacitance variation Δ C-m-C0 of the MEMS capacitor, where m is used to represent a relationship between the capacitance variation and the static capacitance.

The sensitivity Sen of the MEMS system is:

the equivalent Noise voltage Noise of the MEMS system is:

the signal-to-noise ratio SNR of the MEMS system without considering the MEMS part noise is:

wherein, k3 ═ k1 ═ k2, it can be seen that, when the equivalent input noise vn2 of the gain adjustment module 32 is smaller than the equivalent input noise vn1 of the buffer module 31, the signal-to-noise ratio loss in the sensitivity adjustment process can be greatly reduced; when the equivalent input noise vn2 of the gain adjustment module 32 is sufficiently small relative to the equivalent input noise vn1 of the buffer module 31, the signal-to-noise ratio of the MEMS system can be considered as not varying with gain trimming.

Based on this, this embodiment also provides a signal processing circuit. As shown in fig. 1, the apparatus includes a bias voltage generating module 10, a buffer module 31, and a gain adjusting module 32.

The bias voltage generating module 10 is configured to generate and output a bias voltage Vcp, the bias voltage generating module 10 provides the bias voltage Vcp to the capacitive MEMS sensor module 20, and the capacitive MEMS sensor module 20 generates a first voltage signal Vin. The buffer module 31 is connected to the first voltage signal Vin, performs impedance conversion, and outputs a second voltage signal Vs; the gain adjusting module 32 is connected to the output end of the buffer module 31, is connected to the second voltage signal Vs, and feeds back the second voltage signal Vs to the output end of the offset voltage generating module 10 through the second coupling module after performing gain adjustment on the second voltage signal Vs.

It should be understood that the specific structures and connection relationships of the bias voltage generation module 10, the buffer module 31, the capacitive MEMS sensor module 20 and the gain adjustment module 32 have been described above, and are not described in detail herein.

Example two

Fig. 5 is a structural block diagram of the MEMS system provided in this embodiment. As shown in fig. 5, the difference from the first embodiment is that in the present embodiment, the number of the MEMS capacitors is two, two of the MEMS capacitors form a differential capacitor, and the capacitive MEMS sensing module 20 is a differential capacitive MEMS sensing module.

In this embodiment, the bias voltage generating module 10 outputs one bias voltage Vcp through an output end, and an input end of the capacitive MEMS sensing module 20 is connected to the output end of the bias voltage generating module 10 and is used for accessing the bias voltage Vcp. And the two MEMS capacitors generate reverse capacitance variation under the excitation of the sound signal, the signal on one MEMS capacitor can be coupled to the signal on the other MEMS capacitor to be output together, and the function of converting the difference into the single end is completed on the MEMS part. The differential capacitor outputs a first voltage signal Vin representing the sound signal according to the capacitance variation and the bias voltage Vcp, and the first voltage signal Vin is output through an output end of the capacitive MEMS sensing module 20, so that single-ended output of the capacitive MEMS sensing module 20 is realized.

It should be understood that, since the capacitive MEMS sensing module 20 is a single-ended output signal, the buffer module 31 only needs to perform signal processing on the first voltage signal Vin, and the MEMS system is compatible with the common single-input buffer module 31 without redesigning the buffer module 31. Further, the capacitive MEMS sensing module 20 completes the superposition of signals of two MEMS capacitors, and a circuit for superposing signals is not required to be designed in the buffer module 31, so that the packaging process is simpler, and the area of a chip is smaller. Further, the first voltage signal Vin is a superposition of signals on the two MEMS capacitors, which is equivalent to improving the sensitivity of the system, and no other noise is introduced, so that the signal-to-noise ratio (SNR) of the MEMS system can be improved, and the performance of the MEMS system is further improved.

In this embodiment, the capacitance MEMS sensing module 20 is a differential capacitance MEMS microphone, such as a dual-backplate differential capacitance MEMS microphone, a dual-diaphragm differential capacitance MEMS microphone, or a transverse differential capacitance MEMS microphone. However, it should be understood that the capacitive MEMS sensing module 20 in the present invention is not limited to a differential capacitive MEMS microphone, but may also be a differential capacitive MEMS acoustic transducer or a differential capacitive MEMS microphone, etc., and as long as the MEMS sensor supports differential output, the MEMS sensor is within the protection scope of the present invention, and the description thereof is not repeated.

EXAMPLE III

Fig. 6 is a block diagram of the MEMS system provided in this embodiment. As shown in fig. 6, the difference from the second embodiment is that, in the present embodiment, the bias voltage generating module 10 outputs one bias voltage through two output terminals respectively.

Specifically, a first output terminal of the bias voltage generation module 10 outputs a bias voltage Vcp01, a second output terminal of the bias voltage generation module 10 outputs a bias voltage Vcp02, and the capacitive MEMS sensing module 20 is connected to the bias voltage Vcp01 and the bias voltage Vcp 02. The capacitive MEMS sensing module 20 further receives a second common mode voltage Vcom2 through a second high impedance module 34, and outputs a first voltage signal Vin representing the sound signal according to the capacitance variation, the bias voltage Vcp01, the bias voltage Vcp02, and the second common mode voltage Vcom 2.

In this embodiment, the bias voltage generating module 10 includes two third high-resistance modules, namely a third high-resistance module 111 and a third high-resistance module 112, and the charge pump module 12 outputs two basic bias voltages, namely a basic bias voltage Vcp11 and a basic bias voltage Vcp 12. The third high-resistance module 111 is connected to the charge pump module 12, and is configured to access the basic bias voltage Vcp11, and stabilize the basic bias voltage Vcp11 in a high-resistance state, where the bias voltage Vcp01 is described. Similarly, the third high-resistance module 112 is connected to the charge pump module 12, and is configured to switch in the basic bias voltage Vcp12, stabilize the basic bias voltage Vcp12 in a high-resistance state, and output the bias voltage Vcp 02. In this way, the first output terminal and the second output terminal of the bias voltage generating module 10 are both in a high impedance state.

In this embodiment, the second high impedance module 34 and the third high impedance module 111 and the third high impedance module 112 have the same structure, and it should be understood that the second high impedance module 34 and the third high impedance module 111 and the third high impedance module 112 may have different structures.

Specifically, the second high impedance module 34 may also include a second high impedance node and a second low impedance node, where one or at least two second unidirectional conductive units are connected in series between the second high impedance node and the second low impedance node, the second low impedance node is connected to the second common mode voltage Vcom2, and the second high impedance node is connected to the capacitive MEMS sensing module 20.

As an optional embodiment, a fast start circuit may also be connected between the second high-resistance node and the second low-resistance node, so as to accelerate the establishment of the voltage at the second high-resistance node and improve the start speed of the system.

In this embodiment, the second common mode voltage Vcom2 is 0V, but it should not be limited thereto, and the second common mode voltage Vcom2 may be other voltage values.

Further, a first coupling module is connected between the output end of the capacitive MEMS sensing module 20 and the input end of the buffer module 31. In this embodiment, the first coupling module is a coupling capacitor C3, and the coupling capacitor C3 is configured to couple the first voltage signal Vin to the input terminal of the buffer module 31.

Example four

Fig. 7a, 7b and 7c are block diagrams of three MEMS systems provided in this embodiment. As shown in fig. 7a, 7b and 7c, the difference from the first embodiment, the second embodiment and the third embodiment is that in this embodiment, the MEMS system further includes a single-rotation dual module 35. The input end of the single-conversion dual-module 35 is connected to the output end of the buffer module 31 to access the second voltage signal Vs and convert the second voltage signal Vs into a differential signal, and the MEMS system outputs the differential signal, that is, the differential signal is commonly used as the output signals Voutb and Voutn of the MEMS system.

EXAMPLE five

Fig. 8a, 8b and 8c are block diagrams of three MEMS systems provided in this embodiment. As shown in fig. 8a, 8b and 8c, the difference from the first, second and third embodiments is that in this embodiment, the gain coefficient of the gain adjustment module 32 is-1, and at this time, the second voltage signal Vs output by the buffer module 31 and the third voltage signal Vf output by the gain adjustment module 32 constitute a differential signal. The MEMS system outputs a differential signal formed by the second voltage signal Vs and the third voltage signal Vf, that is, the differential signal is commonly used as the output signals Voutm and Voutp of the MEMS system.

EXAMPLE six

Fig. 9a, 9b and 9c are block diagrams of three MEMS systems provided in this embodiment. As shown in fig. 9a, 9b and 9c, the difference from the first, second and third embodiments is that in this embodiment, the MEMS system is a digital MEMS system, the MEMS system further includes a digital processing module 90, and the digital processing module 90 is configured to convert the second voltage signal Vs into the digital voltage signal, that is, the digital voltage signal is used as the output signal Dout of the MEMS system.

Specifically, the digital processing module 90 includes an analog-digital sampling unit 91 and a digital logic unit 92. The input end of the analog-digital sampling unit 91 is connected to the output end of the buffer module 31, and is configured to access the second voltage signal Vs and sample the second voltage signal Vs to obtain a digital sampling signal, thereby completing analog-digital conversion. The input end of the digital logic unit 92 is connected to the output end of the analog-digital sampling unit 91, and is configured to access the digital sampling signal, and perform format conversion on the digital sampling signal under the control of an externally input first enable signal Lr to obtain a digital voltage signal representing the sound signal. In this way, the second voltage signal Vs is converted into a digital voltage signal by the analog-digital sampling unit 91 and the digital logic unit 92, and then output.

Optionally, the analog-digital sampling unit 91 may be a Sigma-Delta, SAR, or noisseshapingsar structure.

In this embodiment, the analog-digital sampling unit 91 is a module with double-ended input and single-ended output, and the digital logic unit 92 is a module with single-ended input and single-ended output. One input end of the analog-digital sampling unit 91 is grounded, and the other input end is connected with the output end of the buffer module 31, so that the normal operation of the analog-digital sampling unit 91 is ensured.

Further, another difference from the first, second and third embodiments is that the digital control module 60 is omitted in this embodiment, the clock signal required by the digital logic unit 92 can be replaced by an external clock signal CLK', and the digital control signal GainCtrl is directly generated by the digital logic unit 92 to implement digital control of the whole MEMS system.

EXAMPLE seven

Fig. 10a, 10b and 10c are block diagrams of three MEMS systems provided in this embodiment. As shown in fig. 10a, 10b and 10c, the difference from the fifth embodiment is that in the present embodiment, the MEMS system is a digital MEMS system, the MEMS system further includes a digital processing module 90, the digital processing module 90 is configured to convert the second voltage signal Vs and the third voltage signal Vf into two digital voltage signals, and the two digital voltage signals also form a differential signal, that is, the differential signal is used as the output signals Doutm and Doutp of the MEMS system.

In this embodiment, the analog-digital sampling unit 91 is a module with double-ended input and double-ended output, and the digital logic unit 92 is a module with double-ended input and double-ended output. And respectively connecting two input ends of the analog-digital sampling unit 91 with the output end of the buffer module 31 and the output end of the gain adjusting module 32, thereby ensuring the normal operation of the analog-digital sampling unit 91.

Further, another difference from the fifth embodiment is that the digital control module 60 is omitted in this embodiment, the clock signal required by the digital logic unit 92 can be replaced by an external clock signal CLK', and the digital control signal GainCtrl is directly generated by the digital logic unit 92 to implement digital control of the whole MEMS system.

In summary, in the MEMS system and the signal processing circuit provided in the embodiments of the present invention, the MEMS capacitor of the capacitive MEMS sensing module generates a capacitance variation under the excitation of an external sound signal, and the capacitive MEMS sensing module is connected to the bias voltage generating module to access the bias voltage, and outputs a first voltage signal representing the sound signal according to the capacitance variation and the bias voltage; accessing the first voltage signal by using a buffer module, performing impedance conversion and outputting a second voltage signal; and accessing the second voltage signal by using a gain adjusting module, performing gain adjustment on the second voltage signal, and feeding back the second voltage signal to the capacitive MEMS sensing module. According to the invention, the positive and negative gain adjustment of the sensitivity of the capacitive MEMS sensing module can be realized through the gain adjustment module, so that the application scene of the MEMS system is enlarged; meanwhile, the loss of the signal-to-noise ratio in the sensitivity adjusting process can be greatly reduced by controlling the equivalent input noise of the gain adjusting module and the buffering module, and the signal-to-noise ratio of the system is kept fixed in the gain adjusting process.

It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.

It should be noted that, although the present invention has been described with reference to the preferred embodiments, the above embodiments are not intended to limit the present invention. It will be apparent to those skilled in the art from this disclosure that many changes and modifications can be made, or equivalents modified, in the embodiments of the invention without departing from the scope of the invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the protection scope of the technical solution of the present invention, unless the content of the technical solution of the present invention is departed from.

It should be further understood that the terms "first," "second," "third," and the like in the description are used for distinguishing between various components, elements, steps, and the like, and are not intended to imply a logical or sequential relationship between various components, elements, steps, or the like, unless otherwise indicated or indicated.

It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present invention. It must be noted that, as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to "a step" or "an apparatus" means a reference to one or more steps or apparatuses and may include sub-steps as well as sub-apparatuses. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or" rather than the definition of a logical "exclusive or" unless the context clearly dictates otherwise. Further, implementation of the methods and/or apparatus of embodiments of the present invention may include performing the selected task manually, automatically, or in combination.

Claims

1. A MEMS system, comprising:

the bias voltage generating module is used for generating bias voltage;

2. The MEMS system of claim 1, wherein the output of the bias voltage generation module and the output of the capacitive MEMS sensing module are both in a high impedance state.

3. The MEMS system of claim 2, wherein the number of the MEMS capacitors is one, and the bias voltage generating module outputs one of the bias voltages through one output terminal.

4. The MEMS system of claim 2, wherein the number of the MEMS capacitors is two, and the two MEMS capacitors produce opposite capacitance variations upon excitation by the acoustic signal.

5. The MEMS system of claim 4, wherein the bias voltage generation module outputs one of the bias voltages through an output terminal.

6. The MEMS system of claim 3 or 5, further comprising:

7. The MEMS system as claimed in claim 4, wherein the bias voltage generating module outputs one of the bias voltages through two output terminals, the capacitive MEMS sensing module further receives a second common mode voltage, and the capacitive MEMS sensing module outputs the first voltage signal according to the capacitance variation, the two bias voltages and the second common mode voltage.

8. The MEMS system of claim 7, further comprising:

9. The MEMS system of claim 7, wherein a first coupling module is coupled between an output of the capacitive MEMS sensing module and an input of the buffer module.

10. The MEMS system of claim 10, wherein the second coupling module comprises:

11. The MEMS system of claim 10, wherein the second coupling module further comprises:

12. The MEMS system of claim 1, wherein the bias voltage generation module comprises:

13. The MEMS system of claim 1, wherein the MEMS system outputs the second voltage signal.

14. The MEMS system of claim 13, further comprising:

15. The MEMS system of claim 1, wherein the gain factor of the gain adjustment module is negative.

16. The MEMS system of claim 15, wherein the gain adjustment module has a gain factor of-1, wherein the second voltage signal output by the buffer module and the signal output by the gain adjustment module form a differential signal, and wherein the MEMS system outputs the differential signal.

17. The MEMS system of claim 1, wherein a gain factor of the gain adjustment module is positive.

18. The MEMS system of any one of claims 13-17, further comprising a digital processing module, the digital processing module comprising:

19. The MEMS system of claim 1, wherein the digital logic unit further outputs a digital control signal driven by an external clock signal and an external first enable signal, the digital control signal being used to implement digital control of the entire MEMS system.

20. The MEMS system of claim 1, further comprising:

21. The MEMS system of claim 1, further comprising:

22. The MEMS system of claim 1, wherein the bias voltage generation module, the buffer module and the gain adjustment module are integrated on a same ASIC chip, and the ASIC chip is connected to the capacitive MEMS sensing module by wire bonding.

23. The MEMS system of claim 22, further comprising:

24. The MEMS system of claim 1, wherein the capacitive MEMS sensing module comprises a capacitive MEMS microphone, a capacitive MEMS acoustic transducer, or a capacitive MEMS microphone.

25. A signal processing circuit, comprising: