Microphone chip integrated with MEMS pressure sensor

Abstract

The invention discloses a microphone chip integrated with an MEMS (Micro Electro Mechanical System) pressure sensor. The piezoresistive MEMS pressure sensor comprises a piezoresistive MEMS pressure sensor and an ASIC chip with a low-offset operational amplifier and a power switch adaptive control circuit. The piezoresistive MEMS pressure sensor is used for detecting the suction intensity; and the ASIC chip controls the driving power of the heating wire based on a signal of the piezoresistive MEMS pressure sensor. The piezoresistive MEMS pressure sensor and the ASIC chip are integrated, the suction intensity can be accurately detected and converted into the control voltage through mutual cooperation of the ASIC chip and the MEMS sensor, the driving power and the lighting intensity of the heating wire are accurately controlled through the voltage, more real user experience is obtained, and the practicability is high. The problems that a traditional scheme is single in function and the inspiration action is prone to misjudgment are solved.

Description

Technical Field

[0001] The present invention relates to the field of MEMS chips, and in particular to a microphone chip integrating a MEMS pressure sensor. Background Art

[0002] The nutrient solution atomization technology controls the opening and closing of the heating wire by detecting the human body's breathing action. When the heating wire is turned on, the nutrient solution will be heated and atomized by the heating wire and enter the body with the human body's inhalation. When a breathing action is completed, the excess nutrient solution gas will be discharged from the body.

[0003] The nutrient solution atomization technology involves a microphone. The traditional microphone consists of a capacitor and an ASIC chip. When there is an inhalation action, the capacitance of the capacitor will change. The ASIC chip detects the change in capacitance and determines that there is an inhalation action. The built-in power tube of the chip is turned on to heat the heating wire, atomize the nutrient solution, and light up the indicator light. When the inhalation action stops, the capacitance of the capacitor is restored, the ASIC chip turns off the power tube, and the indicator light gradually goes out, completing a nutrient solution atomization action. During the inhalation process, if there are abnormal conditions such as chip overheating or long inhalation time, the ASIC chip controls the indicator light to flash at different frequencies and turns off the internal power switch to implement an abnormal state alarm.

[0004] The capacitor of a traditional microphone is composed of a metal cavity. When the inhalation action occurs, the distance between the upper and lower plates of the metal cavity changes, causing the capacitance value to change. The traditional ASIC chip used in the microphone can only detect the action of the capacitance change, but cannot detect the change in the capacitance value. Therefore, it is impossible to accurately simulate the real nutrient solution atomization process. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned background technology, the present invention provides a microphone chip with an integrated MEMS pressure sensor, which is used to simulate the nutrient solution atomization scene more realistically.

[0006] A first aspect of the present invention provides a microphone chip with an integrated MEMS pressure sensor, comprising a piezoresistive MEMS pressure sensor and an ASIC chip with a low offset operational amplifier and a power switch adaptive control circuit;

[0007] The piezoresistive MEMS pressure sensor is used to detect the inhalation intensity;

[0008] The ASIC chip controls the driving power of the heating wire based on the signal of the piezoresistive MEMS pressure sensor.

[0009] Furthermore, the piezoresistive MEMS pressure sensor adopts a thin film cavity structure, and a plurality of piezoresistive strips are generated on the thin film in a central radial shape;

[0010] The radiation edge is composed of two piezoresistive strips, one of which is close to the center of the film and the other is close to the edge of the film; the pressure is determined by detecting the voltage divided by the two piezoresistive strips on the power supply;

[0011] Preferably, there are eight radiation strips, forming eight groups of piezoresistor pairs; each group is composed of two piezoresistor strips, and the piezoresistors are connected to the ASIC chip through deposited metal pins.

[0012] Furthermore, the ASIC chip has a built-in chip select signal, the piezoresistor pairs are selected in turn, the operational amplifier completes all sampling and amplification, and the voltage amplified by the operational amplifier is compared with the fixed ramp signal to generate a square wave signal, which controls the opening and closing of the power tube.

[0013] Preferably, eight groups of piezo-resistance pairs are alternately switched on, and the switching time is 1 ms. The voltage value of each group of piezo-resistance pairs is used to reflect the deformation of the film in one direction. The driving power of the heating wire is proportional to the average deformation of the film in eight directions, that is, proportional to the air inhalation intensity.

[0014] Preferably, the signal of the piezoresistive MEMS pressure sensor is also characterized by light intensity.

[0015] Furthermore, the piezoresistive MEMS pressure sensor and the ASIC chip are interconnected via through silicon vias.

[0016] A second aspect of the present invention provides a nutrient solution atomization scene simulation device, comprising the above-mentioned microphone chip.

[0017] The beneficial effects of the present invention are:

[0018] The present invention integrates a piezoresistive MEMS pressure sensor and an ASIC chip. Through the mutual cooperation of the ASIC chip and the MEMS sensor, the inhalation intensity can be accurately detected and converted into a control voltage. The driving power of the heating wire and the lighting intensity can be accurately controlled through the voltage, thereby obtaining a more realistic user experience and solving the problem that the traditional solution has a single function and the inhalation action is easily misjudged.

[0019] The present invention also designs a special piezoresistive MEMS pressure sensor for the application scenario of the microphone. Through eight sets of centrally symmetrical piezoresistive pairs, it can accurately reflect the average pressure changes of the film in eight directions, making the detection more accurate.

[0020] The power switch adaptive control circuit of the present invention adopts a time accumulation algorithm, simplifies the circuit structure, improves the reliability of the circuit, saves chip costs and ensures pressure detection accuracy.

[0021] The present invention packages the MEMS sensor chip and the ASIC chip together through the through silicon via technology, thereby reducing the volume of the microphone head and lowering the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A top view of the dedicated piezoresistive MEMS pressure sensor of the present invention;

[0023] Figure 2 A cross-sectional view of the dedicated piezoresistive MEMS pressure sensor of the present invention cut from the middle;

[0024] Figure 3 The working principle diagram of the ASIC chip of the present invention;

[0025] Figure 4 The schematic diagram of the power tube driving signal generation of the present invention;

[0026] Figure 5 It is a cross-sectional view of the microphone chip of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] The present application proposes a microphone chip with an integrated MEMS pressure sensor, which is composed of a specially designed piezoresistive MEMS pressure sensor and an ASIC chip with a low-offset operational amplifier and a power switch adaptive control circuit.

[0029] Figure 1 1 is a top view of the piezoresistive MEMS pressure sensor in the embodiment of the present application. The piezoresistive MEMS pressure sensor is composed of a thin film cavity. Sixteen piezoresistive strips 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 10a, 10b, 10c, 10d, 10e, and 10f are grown on the thin film in a centrally symmetrical manner to form eight groups of piezoresistive pairs (i.e., eight groups of piezoresistive pairs are radiated, and each group is a radiation edge); each One group consists of two piezoresistive strips, one close to the center of the film and the other close to the edge of the film. The piezoresistive strips are connected to the ASIC chip through metal aluminum leads 120 and deposited metal pins 110, 111, 112, 113, 114, 115, 116, 117, 118, and 119; one end of the piezoresistive pair is connected to the power supply and the other end is connected to the ground. All power supplies are connected together, and all grounds are also connected together. The power supply is connected through pin 110, and the ground is connected through pin 111.

[0030] Furthermore, when there is no inhalation action, that is, when the film area 130 is not deformed, the resistance of the piezoresistors is equal, and the voltage at the connection point of each set of piezoresistors is 1 / 2 of the power supply; when the inhalation action occurs, the pressure difference on both sides of the film changes, and the film area 130 is deformed. Due to the application scenario of the microphone, the deformation at the center of the film area 130 is the largest, and the deformation is smaller as it is closer to the edge of the sensor, which makes the piezoresistors near the center of the film change more, and the piezoresistors near the edge of the film change less. Therefore, the voltage at the connection point of the piezoresistors will deviate from 1 / 2 of the power supply. The greater the voltage deviation, the greater the deformation of the film and the more intense the inhalation action.

[0031] Collecting the deviation voltages in eight directions respectively can accurately reflect the deformation amplitude of the film, which reflects the magnitude of the pressure. Even if the maximum deformation point of the film deviates from the center point, eight sets of centrally symmetrical resistor pairs can obtain eight sets of voltage differences. The influence of the offset can be eliminated by cumulative averaging, making the detection result more accurate.

[0032] Figure 2 It is a cross-sectional view of a piezoresistive MEMS pressure sensor seen along the piezoresistors 100, 101, 109, and 108. The silicon base 210 in the embodiment of the present application is formed into a cavity and a thin film area 130 by anisotropic etching. When the pressure sensor is subjected to gas pressure, the thin film area 130 will deform, causing the resistance of the piezoresistive strips 100, 101, 109, 108, etc. to change.

[0033] After completing thin film etching, piezoresistor generation, and metal deposition, through silicon vias 200 and 201 are generated from the bottom of the silicon substrate 210. The function of the through silicon vias is to lead out the corresponding pins from the bottom of the silicon substrate 210, so as to facilitate connecting the pins of the MEMS pressure sensor with the corresponding pins on the ASIC chip.

[0034] The ASIC chip described in the embodiment of the present application has a low-offset operational amplifier. By increasing the input pair tube area and the resistor trimming technology, the input offset voltage of the operational amplifier is less than 100uV, and the measurement accuracy of the operational amplifier can reach 1mV. At the same time, the chip has a built-in chip select signal, and eight groups of piezoresistance pairs are selected in turn. The selection time of each group is 1ms. One operational amplifier can complete all sampling and amplification functions, saving chip area. At the same time, the fixed selection time also provides help for the adaptive adjustment of the power switch.

[0035] Figure 331 is a working principle diagram of the ASIC chip in this embodiment. It is powered by an input power supply 315. The middle connection points of each group of piezoresistors of the MEMS pressure sensor are respectively connected to the built-in switches 300, 301, 302, 303, 304, 305, 306, and 307 of the ASIC chip. The opening and closing of the switches are controlled by a chip selection signal 330 generated by a logic control module 316. If the switch 300 is selected to be turned on, the divided voltage of the piezoresistors 100 and 101 is sent to the low offset operational amplifier 310. The resistors 320 and 321 form a negative feedback loop. The amplification factor of the operational amplifier 310 is determined by the ratio of the resistors 320 and 321. In this embodiment, the amplification factor of the operational amplifier is 2 times.

[0036] In some embodiments, the ASIC chip integrates a power switch adaptive control circuit, and the voltage amplified by the operational amplifier is compared with a fixed ramp signal to generate a square wave signal with a specific duty cycle. The higher the voltage, the greater the duty cycle. The square wave signal controls the turning on and off of the power tube. The greater the duty cycle, the longer the power tube is turned on, and the greater the driving power of the heating wire.

[0037] The eight groups of piezoresistors are switched on alternately, and the switching time is 1ms. Since the inhalation time is usually more than 1s, the eight groups of piezoresistors can be considered to be evenly switched on during the entire inhalation cycle. The voltage value of each group of piezoresistors reflects the deformation of the film in one direction. Therefore, the driving power of the heating wire is proportional to the average deformation of the film in eight directions, that is, proportional to the inhalation intensity. The power switch adaptive control circuit avoids the use of complex high-precision analog-to-digital converters, simplifies the circuit structure, and does not affect the detection accuracy.

[0038] Furthermore, the output voltage of the operational amplifier 310 is compared with the ramp signal 331 generated by the logic control module 316 through the comparator 311 to generate a square wave signal 332 with a certain duty cycle. The square wave signal 332 controls the switch of the power tube 313 (PMOS) through the power tube driver buffer 312, thereby controlling the heating power on the heating wire 322. The square wave signal 332 also controls the current of the LED indicator light 323 by controlling the current flowing through the voltage-controlled current source 314. The greater the deformation of the film area 130, the greater the voltage change at the piezoresistive connection point, and the voltage change at the piezoresistive connection point is inversely proportional to the duty cycle of the square wave signal 332. The turn-on time of the power tube 313 and the current flowing through the voltage-controlled current source 314 are also inversely proportional to the duty cycle of the square wave signal 332. Therefore, the smaller the duty cycle of the square wave signal 332, that is, the greater the deformation of the film area 130, the longer the turn-on time of the power tube 313, and the greater the current flowing through the voltage-controlled current source 314, thereby making the heating power on the heating wire 322 higher and the brightness of the LED indicator light 323 higher.

[0039] Figure 4: is a schematic diagram of the power tube drive signal generation principle of this embodiment, taking the i-th and i+1-th piezoresistance pairs as an example for explanation:

[0040] Since the gate time of each channel is the same, T i =T i+1 =T on , the ramp signal 331 remains unchanged during the entire operation, with its lowest level being 0 and its highest level being the power supply voltage VDD. Assuming that the slope of the ramp signal 331 is S, when the film of the MEMS pressure sensor is not deformed, that is, when the pressure difference is 0, all the piezoresistors have the same resistance value, and the voltage at the connection point of the piezoresistors is 1 / 2 of the power supply voltage, the output level 400 after amplification by the operational amplifier 310 is the power supply voltage VDD.

[0041] When the pressure sensor film is deformed, the voltage change at the connection point of the i-th piezoresistance pair is ΔV i , after being amplified by the operational amplifier 310, it becomes 2ΔV i , then the output level 401 of the operational amplifier 310 is VDD / 2-2ΔV i , the duty cycle of the driving signal 332 when the i-th channel is selected can be obtained: i =1-2ΔV i / S.

[0042] Assuming that the heating power of the heating wire 322 is P when the power tube 313 is fully turned on, it can be known that when the i-th channel is selected, its output level is 402, and the heating power of the heating wire 322 is 2ΔV i P / S; Similarly, when the i+1 channel is enabled, the heating power of the heating wire 322 is 2ΔV i+1 P / S, since there are a total of 8 piezoresistance pairs that are sequentially selected, it can be obtained that in 8 T on The average heating power of the heating wire 322 during the cycle:

[0043]

[0044] In the formula, S and P are fixed values, so the average heating power P on the heating wire 322 is av It is proportional to the average voltage change of the 8-way piezoresistor pair, that is, proportional to the average deformation of the pressure sensor film.

[0045] In actual work, since the inhalation time is not fixed, the working time of the pressure sensor will not be exactly 8T each time. on Integer multiples of T, there are always several piezoresistance pairs that will be selected one more time each time, so T on It should be small enough relative to the total time of each operation so that the error caused by multiple strobes can be ignored.

[0046] In this embodiment, when the level of the power tube driving signal 332 is high, the power tube is turned off, so the opening time of the power tube 313 is 1-d, and the driving power of the power tube 313 is inversely proportional to the duty cycle of the driving signal 332.

[0047] Based on the above records, the ASIC control chip described in this embodiment controls the driving power of the heating wire by detecting the change in pressure. The greater the pressure change, the greater the driving power of the heating wire. The greater the pressure change, the more intense the inhalation action, so the user experience is more realistic.

[0048] Figure 5 It is a cross-sectional view of the microphone chip of the embodiment of the present application. The pins of the piezoresistive MEMS pressure sensor die 522 are connected to the pins 500, 501, 502, 503, etc. of the ASIC chip die 520 through silicon vias 200, 201, etc., and the pins 500, 503 are bound to the package base 521 through metal wires 510, forming a microphone chip. In the design, the pin positions on the ASIC chip that are connected to the corresponding MEMS pressure sensors must correspond one to one.

[0049] In summary, the microphone chip with integrated MEMS pressure sensor proposed in the embodiment of the present application, whose pressure sensor is combined with the power switch adaptive control circuit, can automatically track the inhalation intensity, thereby controlling the driving power of the heating wire and the brightness of the indicator light. The greater the inhalation intensity, the greater the driving power of the heating wire, and the more nutrient solution atomized gas is generated, making the user experience more realistic.

[0050] The above is only a partial implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A microphone chip with integrated MEMS pressure sensor, including a piezoresistive MEMS pressure sensor and an ASIC chip with a low offset operational amplifier and a power switch adaptive control circuit; The piezoresistive MEMS pressure sensor is used to detect the inhalation intensity; The ASIC chip controls the driving power of the heating wire based on the signal of the piezoresistive MEMS pressure sensor.

2. The microphone chip with integrated MEMS pressure sensor according to claim 1, characterized in that: The piezoresistive MEMS pressure sensor adopts a thin film cavity structure, and a plurality of piezoresistive strips are generated on the thin film in a central radial shape; The radiating edge is composed of two piezoresistive strips, one of which is close to the center of the film and the other is close to the edge of the film; the pressure is determined by detecting the voltage divided by the two piezoresistive strips on the power supply.

3. The microphone chip integrated with a MEMS pressure sensor according to claim 2, characterized in that: There are eight radiation strips, forming eight groups of piezoresistor pairs; each group is composed of two piezoresistor strips, and the piezoresistors are connected to the ASIC chip through deposited metal pins.

4. The microphone chip with integrated MEMS pressure sensor according to claim 1, characterized in that: The ASIC chip has a built-in chip selection signal, the piezoresistor pairs are selected in turn, the operational amplifier completes all sampling and amplification, and the voltage amplified by the operational amplifier is compared with the fixed ramp signal to generate a square wave signal, which controls the opening and closing of the power tube.

5. The microphone chip with integrated MEMS pressure sensor according to claim 3, characterized in that: Eight groups of piezo-resistance pairs are alternately switched on, and the switching time is 1ms. The voltage value of each group of piezo-resistance pairs is used to reflect the deformation of the film in one direction. The driving power of the heating wire is proportional to the average deformation of the film in eight directions, that is, proportional to the air inhalation intensity.

6. The microphone chip with integrated MEMS pressure sensor according to claim 3, characterized in that: The signal of the piezoresistive MEMS pressure sensor is also characterized by the intensity of the light.

7. A microphone chip integrated with a MEMS pressure sensor according to any one of claims 1 to 6, characterized in that: The piezoresistive MEMS pressure sensor and the ASIC chip are interconnected via through silicon vias.

8. A nutrient solution atomization scene simulation device, comprising the microphone chip according to claim 7.

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