CN114222232B

CN114222232B - MEMS system and signal processing circuit

Info

Publication number: CN114222232B
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: 2024-06-28
Anticipated expiration: 2041-12-31
Also published as: CN114222232A

Abstract

The invention provides a MEMS system and a signal processing circuit, wherein the MEMS capacitance of a capacitive MEMS sensing module generates capacitance variation under the excitation of an external sound signal, and the capacitive MEMS sensing module is connected with a bias voltage generating module to be connected with 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 the buffer module, performing impedance conversion, and outputting a second voltage signal; and accessing the second voltage signal by using the gain adjusting module, performing gain adjustment on the second voltage signal, and feeding back the second voltage signal to the capacitive MEMS sensing module. 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 signal-to-noise ratio loss in the sensitivity adjustment process can be greatly reduced by controlling the equivalent input noise of the gain adjustment module and the buffer module, and the signal-to-noise ratio of the system is kept fixed in the gain adjustment process.

Description

MEMS system and signal processing circuit

Technical Field

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

Background

Capacitive MEMS microphones are MEMS (Micro-Electro-MECHANICAL SYSTEM, microelectromechanical system) devices fabricated using micromachining processes. The capacitive MEMS microphone has the advantages of small volume, high sensitivity and good compatibility with the existing semiconductor technology, and is widely applied to mobile terminals such as mobile phones.

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

At present, the vibrating diaphragm and the backboard electrode can be manufactured together, the distance is less than 1.5um, the performance of the capacitive MEMS microphone is greatly improved, along with the improvement of the sensitivity of the capacitive MEMS microphone, a MEMS microphone device with higher signal to noise ratio level can be manufactured, but the sensitivity can not be adjusted after the preparation of the capacitive MEMS microphone is finished at present, and when the sensitivity exceeds the specification, the use of a low-sensitivity scene can be limited.

Disclosure of Invention

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

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

The bias voltage generation module is used for generating bias voltage;

The capacitive MEMS sensing module comprises an MEMS capacitor, wherein the MEMS capacitor generates capacitance variation under the excitation of an external sound signal, and is connected with the bias voltage generation module to be connected with the bias voltage, and outputs 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 be connected with the first voltage signal, perform impedance conversion and output a second voltage signal;

the gain adjusting module is connected with the output end of the buffer module so as to be connected with the second voltage signal, and the second voltage signal is subjected to gain adjustment and then fed back to the output end of the bias voltage generating module through the second coupling module.

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

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

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

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

Optionally, the method further comprises:

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 generating module outputs one bias voltage through two output ends respectively, the capacitive MEMS sensing module is further connected to 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 comprises:

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:

the charge pump module is used for outputting basic bias voltage; and

And the third high-resistance module is connected with the charge pump module so as to be connected with 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 comprises:

and the single-conversion double-module is connected with the output end of the buffer module so as to be connected with the second voltage signal, and converts 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, the 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 is 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 outputs a digital control signal under the driving of an external clock signal and an external first enabling signal, where the digital control signal is used to implement digital control of the whole MEMS system.

Optionally, the method further comprises:

And the digital control module is used for outputting a digital control signal under the drive of the 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 comprises:

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

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

Optionally, the method further comprises:

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 comprises 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:

a bias voltage generation module for generating and outputting a bias voltage, the bias voltage generation module providing the bias voltage to a capacitive MEMS sensor module, the capacitive MEMS sensor module generating a first voltage signal;

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

The gain adjusting module is connected with the output end of the buffer module, is connected with the second voltage signal, and feeds back the second voltage signal 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 capacitance of the capacitive MEMS sensing module generates capacitance variation under the excitation of an external sound signal, and the capacitive MEMS sensing module is connected with the bias voltage generating module to be connected with the bias voltage and outputs a first voltage signal representing the sound signal according to the capacitance variation and the bias voltage; the buffer module is used for accessing the first voltage signal, performing impedance conversion and outputting a second voltage signal; and accessing the second voltage signal by using a gain adjustment module, performing gain adjustment on the second voltage signal, and feeding back the second voltage signal to the capacitive MEMS sensing module. 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 signal-to-noise ratio loss in the sensitivity adjustment process can be greatly reduced by controlling the equivalent input noise of the gain adjustment module and the buffer module, and the signal-to-noise ratio of the system is kept fixed in the gain adjustment process.

Drawings

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

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

FIG. 3 is a circuit diagram of a fast start circuit according to a first 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;

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

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

fig. 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 illustrating a seventh embodiment of the present invention;

wherein, the reference numerals are as follows:

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

Clk-clock signal; CLK' -an external clock signal; vcp, vcp01, vcp 02-bias voltages; vin-first voltage signal; vcp1, vcp11, vcp 12-base bias voltages; vs-a second voltage signal; vf-a third voltage signal; vout, voutm, voutp, voutb, voutn, dout, doutm, doutp, doutb, doutn-an output signal of the MEMS system; gainCtrl-digital control signals; vcom 1-a first common mode voltage; vcom 2-a second common mode voltage; vcom 3-third common mode voltage; v1-a third high resistance node; v2-a third low resistance node; vdd-constant supply voltage; VDD-an external supply voltage; din-an external second enable signal; lr-an external first enable signal; gnd-ground; k-node; c1, C3-coupling resistance; and C2-adjusting resistance.

Detailed Description

Specific embodiments of the present invention will be described in more detail below with reference to the drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.

Example 1

Fig. 1 is a block diagram of the MEMS system according to the present embodiment. As shown in fig. 1, the MEMS system includes:

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

The capacitive MEMS sensing module 20 comprises a MEMS capacitor, wherein the MEMS capacitor generates a capacitance variation under the excitation of an external sound signal, the capacitive MEMS sensing module 20 is connected with the bias voltage generating module 10 to be connected with 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, so as to access the first voltage signal Vin and perform impedance conversion, and output a second voltage signal Vs;

The gain adjustment module 32 is connected to the output end of the buffer module 31 and the capacitive MEMS sensing module 20, so as to access the second voltage signal Vs, and perform gain adjustment on the second voltage signal Vs, and then feed back the second voltage signal Vs to the output end of the bias voltage generation module 10 through the 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 is used 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 sensor module 20 is a capacitive MEMS microphone. It should be understood that the capacitive MEMS sensing module 20 of the present invention is not limited to a capacitive MEMS microphone, but may be a capacitive MEMS acoustic transducer or a capacitive MEMS microphone, etc., and will not be explained here.

Further, the MEMS system further includes a first high-resistance module 33, one end of the first high-resistance 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 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 working point for the output end of the capacitive MEMS sensing module 20.

With continued reference to fig. 1, the output end of the capacitive MEMS sensor module 20 is in a high-resistance state, and the output first voltage signal Vin has no driving capability. For subsequent processing, the input end of the buffer module 31 is connected to the output end of the capacitive MEMS sensor module 20, and is used for accessing the first voltage signal Vin and performing impedance conversion (high-impedance state to low-impedance state) to output a second voltage signal Vs, thereby enhancing the 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 adjustment 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 subjected to gain adjustment.

It should be appreciated that the gain adjustment module 32 may be a conventional 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 terminal of the bias voltage generating module 10, and thus to the capacitive MEMS sensor module 20, that is, to couple the third voltage signal Vf to the input terminal of the MEMS capacitor. The gain adjustment module 32 and the second coupling module form a feedback loop, and when the feedback coefficient on the feedback loop is positive, the feedback loop is positive feedback, so that the positive gain adjustment of the sensitivity of the capacitive MEMS sensing module 20 can be realized; conversely, when the feedback coefficient on the feedback loop is negative, the feedback loop is negative feedback, so that negative gain adjustment of the sensitivity of the capacitive MEMS sensing module 20 can be realized. It can be seen that, in this embodiment, positive and negative gain adjustment of the sensitivity of the capacitive MEMS sensor module 20 can be achieved through the gain adjustment module 32 and the second coupling module, so as to expand the application scenario of the MEMS system.

In this embodiment, the second coupling module includes a coupling capacitor C1. The 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 the 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 an adjusting capacitor C2, a first end of the adjusting capacitor C2 is connected to a second end of the coupling capacitor C1, and a second end of the adjusting capacitor C2 is connected to the third common mode voltage Vcom3.

The coupling capacitor C1 and the adjusting capacitor C2 may be capacitors with adjustable capacitance values, so that the sensitivity of the capacitive MEMS sensor module 20 may 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 capacitors with fixed capacitance values, so that the sensitivity of the capacitive MEMS sensor module 20 may be adjusted by adjusting the gain coefficient of the gain adjusting module 32. Further, the coupling capacitor C1 and the adjusting capacitor C2 may be a capacitor with an adjustable capacitance value, and the other capacitor with a fixed capacitance value, which is not illustrated here.

As an alternative embodiment, the adjustment capacitor C2 may be omitted, since the gain adjustment 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, where the clock signal generating module 40 provides the clock signal Clk to the MEMS system as a whole, and a 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 to 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 generating 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-resistance 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 in a high-resistance state for output, so that the output end of the bias voltage generating module 10 is in a high-resistance state.

It should be appreciated that the higher the bias voltage Vcp is theoretically, the better, but in view of process withstand voltage, the bias voltage Vcp is typically, but not limited to, 4V-15V.

Further, the capacitive MEMS sensing module 20 may generate a pull-in phenomenon (the vibrating diaphragm of the MEMS capacitor is stuck to the backplate electrode) under the excitation of the excessive sound signal, and when the capacitive MEMS sensing module 20 generates the pull-in phenomenon, a jump of the MEMS capacitor (the MEMS capacitor suddenly becomes large), and meanwhile, the leakage of the backplate electrode of the MEMS capacitor increases, which results in a jump of the first voltage signal Vin output by the capacitive MEMS sensing module 20, and the jump is maintained for a period of time, which further results in a significant decrease of 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 the input end of the pull-in detecting module 13 may be connected to a voltage signal (hereinafter referred to as an internal signal) that characterizes the sound signal. When the MEMS capacitor generates a pull-in phenomenon, the pull-in detection module 13 pulls down the bias voltage Vcp when the internal signal jumps, thereby reducing the voltage value of the bias voltage Vcp (for example, the bias voltage Vcp may be pulled down to the ground Vss, thereby grounding the bias voltage Vcp to the ground Vss), releasing the charge on the back plate electrode of the MEMS capacitor, losing the effect of the electric field force, the diaphragm of the MEMS capacitor will spring back under the self elastic effect, and releasing the pull-in state, so as to quickly restore the sensitivity of the system.

It should be appreciated that the internal signal may be, for example, any voltage signal capable of characterizing the sound signal, such as the first voltage signal Vin, the second voltage signal Vs, the third voltage signal Vf, etc., as the present invention is not limited in this regard. In this embodiment, the input end of the pull-in detecting module 13 is connected to the output end of the buffering module 31, and is used for receiving the second voltage signal Vs, where the second voltage signal Vs is used as the internal signal.

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

Fig. 2 is a circuit diagram of the third high-resistance module 11 according to the present embodiment. As shown in fig. 1 and 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 conductive units 801 connected in series are disposed 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 anode and the cathode of the diode 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 and is used for accessing the basic bias voltage Vcp1, and the third high-resistance node V2 is connected to the capacitive MEMS sensing module 20 and is used 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 use the diode-like I-V characteristic to make it have high-resistance characteristic in 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 a fast start circuit according to the present embodiment. As shown in fig. 3, a fast start circuit 802 may also be connected between the third high-resistance node V2 and the third low-resistance node V1. When the voltages of the third low-resistance node V1 and the third high-resistance node V2 are close, the voltage on the third high-resistance node V2 is built very slowly, the quick start circuit 802 in this embodiment is equivalent to a switch, and when the quick start circuit 802 is turned on, the third low-resistance node V1 can quickly charge and discharge the third high-resistance node V2, so that the voltage on the third high-resistance node V2 is built faster, the quick 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 be a diode, but may be two MOS transistors connected by diode connection.

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

As an alternative embodiment, a fast starting 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 starting speed of the system.

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

With continued reference to fig. 1, in this embodiment, the MEMS system further includes an LDO module 50, where the LDO module 50 can receive an external power supply voltage VDD and accordingly provide a constant power supply voltage VDD to the buffer module 31 and/or the gain adjustment module 32, so as to improve the operation performance of the MEMS system.

Further, in this embodiment, the MEMS system further includes a digital control module 60, where 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 the driving of the clock signal Clk and the external second enable signal Din. The digital control signal GainCtrl is used to implement digital control of the entire 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 special test modes, etc.; 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 generating module 10, the buffer module 31, the gain adjusting module 32, the first high-resistance module 33, the clock signal generating 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 sensor module 20 by wire bonding, so as to implement signal intercommunication.

Further, the MEMS system further includes an ESD module 70, where the ESD module 70 is connected to the ASIC chip and is configured to ESD-protect 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 may be output through the ESD module 70, and a signal (e.g., the external second enable signal Din or the external power supply voltage VDD, etc.) externally input to the MEMS system may be input into the MEMS system through the ESD module 70, thereby improving the ESD performance of the MEMS system.

Further, the signal-to-noise ratio loss in the sensitivity adjustment process can be greatly reduced by controlling the equivalent input noise of the gain adjustment module 32 and the buffer module 31, and the signal-to-noise ratio of the system is kept constant in 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 adjustment module 32 be k1, the gain coefficient of the gain adjustment module 32, the coupling capacitor C1 and the adjustment capacitor C2 after gain adjustment is completed together be k2, the equivalent input noise of the buffer module 31 be vn1, the equivalent input noise of the gain adjustment module 32 be vn2, the static capacitance of the MEMS capacitor be C0, the parasitic capacitance be Cp, and the acoustic signal (InPressure) cause the capacitance variation Δc=mxc0 of the MEMS capacitor, where m is used to represent the 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 as follows:

The signal-to-noise ratio SNR of the MEMS system is as follows, without considering the MEMS partial noise:

Where 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 to be unchanged with the gain trimming.

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

Wherein 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 the first voltage signal Vin. The buffer module 31 is connected to the first voltage signal Vin and performs impedance conversion to output a second voltage signal Vs; the gain adjustment module 32 is connected to the output end of the buffer module 31, and is connected to the second voltage signal Vs, and performs gain adjustment on the second voltage signal Vs, and then feeds back the second voltage signal Vs to the output end of the bias voltage generation module 10 through the second coupling module.

It should be understood that the specific structures and connection relationships of the bias voltage generating module 10, the buffer module 31, the capacitive MEMS sensor module 20 and the gain adjusting module 32 are described above, and will not be described herein.

Example two

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

In this embodiment, the bias voltage generating module 10 outputs the bias voltage Vcp through an output end, and the input end of the capacitive MEMS sensing module 20 is connected to the output end of the bias voltage generating module 10, so as to access the bias voltage Vcp. And the two MEMS capacitors generate reverse capacitance variation under the excitation of the sound signals, the signals on one MEMS capacitor can be coupled to the signals on the other MEMS capacitor to be output together, and the function of converting the difference into the single end is completed in 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 one output end of the capacitive MEMS sensing module 20, so as to realize single-ended output of the capacitive MEMS sensing module 20.

It should be appreciated that since the capacitive MEMS sensor module 20 is a single-ended output signal, the buffer module 31 only needs to process the first voltage signal Vin, and the MEMS system can be compatible with a common single-input buffer module 31, without redesigning the buffer module 31. Further, the capacitive MEMS sensing module 20 itself completes the superposition of signals of two MEMS capacitors, and no circuit for superposing signals is required to be designed in the buffer module 31, so that the packaging process is simpler and the area of the chip is smaller. Further, the first voltage signal Vin is a superposition of signals on 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 capacitive MEMS sensor module 20 is a differential capacitive MEMS microphone, such as a dual-backplate differential capacitive MEMS microphone, a dual-diaphragm differential capacitive MEMS microphone, or a lateral differential capacitive MEMS microphone. However, it should be understood that the capacitive MEMS sensor module 20 in the present invention is not limited to a differential capacitive MEMS microphone, but may be a differential capacitive MEMS acoustic transducer, a differential capacitive MEMS microphone, or the like, and any MEMS sensor that supports differential output is within the scope of the present invention, and will not be explained here.

Example III

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

Specifically, the first output terminal of the bias voltage generating module 10 outputs a bias voltage Vcp01, the second output terminal of the bias voltage generating module 10 outputs a bias voltage Vcp02, and the capacitive MEMS sensing module 20 interfaces the bias voltage Vcp01 and the bias voltage Vcp02. The capacitive MEMS sensing module 20 is further connected to 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 base bias voltages, namely a base bias voltage Vcp11 and a base bias voltage Vcp12. 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, and the bias voltage Vcp01. Similarly, the third high-resistance module 112 is connected to the charge pump module 12, and is configured to access the base bias voltage Vcp12, stabilize the base bias voltage Vcp12 in a high-resistance state, and output the bias voltage Vcp02. In this way, the first output terminal and the second output terminal of the bias voltage generating module 10 are both in a high-resistance state.

In this embodiment, the second high-resistance module 34 has the same structure as the third high-resistance module 111 and the third high-resistance module 112, and it should be understood that the second high-resistance module 34 may also have a different structure from the third high-resistance module 111 and the third high-resistance module 112.

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

As an alternative embodiment, a fast starting 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 on the second high-resistance node and increase the starting speed of the system.

In the embodiment, the second common-mode voltage Vcom2 is 0V, but not limited to this, the second common-mode voltage Vcom2 may be another voltage value.

Further, a first coupling module is connected between the output end of the capacitive MEMS sensor 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 end of the buffer module 31.

Example IV

Fig. 7a, fig. 7b and fig. 7c are block diagrams of the three MEMS systems according to the present embodiment. As shown in fig. 7a, 7b and 7c, the difference between the first embodiment, the second embodiment and the third embodiment is that in this embodiment, the MEMS system further includes a single-turn dual module 35. The input end of the single-turn 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 used together as output signals Voutb and Voutn of the MEMS system.

Example five

Fig. 8a, 8b and 8c are block diagrams of three MEMS systems according to the present embodiment. As shown in fig. 8a, 8b and 8c, the difference between the second voltage signal Vs output by the buffer module 31 and the third voltage signal Vf output by the gain adjustment module 32 is that the gain coefficient of the gain adjustment module 32 is-1 in this embodiment. The MEMS system outputs a differential signal composed of the second voltage signal Vs and the third voltage signal Vf, that is, the differential signal is used together as output signals Voutm and Voutp of the MEMS system.

Example six

Fig. 9a, 9b and 9c are block diagrams of three MEMS systems according to the present embodiment. As shown in fig. 9a, 9b and 9c, the difference between the first embodiment, the second embodiment and the third embodiment is that in this embodiment, the MEMS system is a digital MEMS system, and the MEMS system further includes a digital processing module 90, where 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 used for accessing the second voltage signal Vs and sampling 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 used for accessing the digital sampling signal, and performing format conversion on the digital sampling signal under the control of the first enable signal Lr input from the outside, so as 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 output by the analog-digital sampling unit 91 and the digital logic unit 92.

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

In this embodiment, the analog-digital sampling unit 91 is a module with two-end input and single-end output, and the digital logic unit 92 is a module with single-end input and single-end 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 may be replaced by an external clock signal CLK', and the digital control signal GainCtrl is directly generated by the digital logic unit 92, so as to implement digital control of the whole MEMS system.

Example seven

Fig. 10a, 10b and 10c are block diagrams of three MEMS systems according to the present embodiment. As shown in fig. 10a, 10b and 10c, the difference from the fifth embodiment is that in this embodiment, the MEMS system is a digital MEMS system, and the MEMS system further includes a digital processing module 90, where 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 differential signals, that is, the differential signals are used as output signals Doutm and Doutp of the MEMS system.

In this embodiment, the analog-digital sampling unit 91 is a dual-input dual-output module, and the digital logic unit 92 is a dual-input dual-output module. The two input ends of the analog digital sampling unit 91 are respectively connected with the output end of the buffer module 31 and the output end of the gain adjustment module 32, so as to ensure 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 may be replaced by an external clock signal CLK', and the digital control signal GainCtrl is directly generated by the digital logic unit 92, so as to implement digital control of the whole MEMS system.

In summary, in the MEMS system and the signal processing circuit provided by 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; the buffer module is used for accessing the first voltage signal, performing impedance conversion and outputting a second voltage signal; and accessing the second voltage signal by using a gain adjustment module, performing gain adjustment on the second voltage signal, and feeding back the second voltage signal to the capacitive MEMS sensing module. 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 signal-to-noise ratio loss in the sensitivity adjustment process can be greatly reduced by controlling the equivalent input noise of the gain adjustment module and the buffer module, and the signal-to-noise ratio of the system is kept fixed in the gain adjustment process.

It should be noted that, in the present description, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system disclosed in the embodiment, the description is relatively simple because of corresponding to the method disclosed in the embodiment, and the relevant points refer to the description of the method section.

It should be further noted that although the present invention has been disclosed in the preferred embodiments, the above embodiments are not intended to limit the present invention. Many possible variations and modifications of the disclosed technology can be made by anyone skilled in the art without departing from the scope of the technology, or the technology can be modified to be equivalent. Therefore, any simple modification, equivalent variation and modification of the above embodiments according to the technical substance of the present invention still fall within the scope of the technical solution of the present invention.

It should be further understood that the terms "first," "second," "third," and the like in this specification are used merely for distinguishing between various components, elements, steps, etc. in the specification and not for indicating a logical or sequential relationship between the various components, elements, steps, etc., unless otherwise indicated.

It should also be understood that the terminology described 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 as having the definition of a logical "or" rather than a logical "exclusive or" unless the context clearly indicates the contrary. Furthermore, implementation of the methods and/or apparatus in embodiments of the invention may include performing selected tasks manually, automatically, or in combination.

Claims

1. A MEMS system, comprising:

The bias voltage generation module is used for generating bias voltage;

The gain adjusting module is connected with the output end of the buffer module to be connected with the second voltage signal, and the second voltage signal is subjected to gain adjustment and then fed back to the output end of the bias voltage generating module through the second coupling module, and the capacitive MEMS sensing module, the buffer module, the gain adjusting module and the second coupling module form a feedback loop to adjust the sensitivity of the capacitive MEMS sensing module;

And when the feedback loop is positive feedback, positive gain adjustment of the capacitive MEMS sensing module is realized, and when the feedback loop is negative feedback, negative gain adjustment of the capacitive MEMS sensing module is realized.

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 resistance state.

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

4. The MEMS system of claim 2, wherein the number of MEMS capacitances is two, the two MEMS capacitances producing an opposite capacitance change upon excitation of the acoustic signal.

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

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

7. The MEMS system of claim 4, wherein the bias voltage generation module outputs one of the bias voltages through two output terminals, respectively, the capacitive MEMS sensing module is further coupled to 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 connected between an output of the capacitive MEMS sensing module and an input of the buffer module.

10. The MEMS system of claim 1, 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:

the charge pump module is used for outputting basic bias voltage; and

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 a gain factor of the gain adjustment module is negative.

16. The MEMS system of claim 15, wherein the gain factor 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.

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

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

19. The MEMS system of claim 18, wherein the digital logic unit is further configured to output a digital control signal driven by an external clock signal and an external first enable signal, the digital control signal configured to enable digital control of the MEMS system as a whole.

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 that is wired to the capacitive MEMS sensing module.

23. The MEMS system, as recited in 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:

The gain adjusting module is connected with the output end of the buffer module, is connected with the second voltage signal, and feeds back the second voltage signal to the output end of the bias voltage generating module through the second coupling module after performing gain adjustment, and the capacitive MEMS sensing module, the buffer module, the gain adjusting module and the second coupling module form a feedback loop to adjust the sensitivity of the capacitive MEMS sensing module;