MEMS transducer system and associated methods

Patent metadata

Field	Value
Publication number	US-10972848-B2
Application number	US-201916598799-A
Country	US
Kind code	B2
Filing date	Oct 10, 2019
Priority date	Mar 31, 2017
Publication date	Apr 6, 2021
Grant date	Apr 6, 2021

Abstract

The disclosure provides a system, comprising: a MEMS capacitive transducer, comprising one or more first capacitive plates coupled to a first node and one or more second capacitive plates coupled to a second node; biasing circuitry coupled to the first node, operable to provide a biasing voltage to the one or more first capacitive plates; and test circuitry coupled to the second node, operable to: selectively apply one or more current sources to the second node, so as to charge and discharge the MEMS capacitive transducer and so vary a signal based on a voltage at said second node between an upper value and a lower value; determine a parameter that is indicative of a time period of the variation of the signal; and determine a capacitance of the MEMS capacitive transducer based on the parameter that is indicative of the time period.

First claim

The invention claimed is:

1. A system, comprising:
a MEMS capacitive transducer, comprising one or more first capacitive plates coupled to a first node and one or more second capacitive plates coupled to a second node;
biasing circuitry coupled to the first node, operable to provide a biasing voltage to the one or more first capacitive plates;
output circuitry coupled to the second node, for generating an output signal; and
capacitive circuitry coupled to the first node, comprising a charge amplifier arranged in a feedback loop, the feedback loop further comprising a first capacitor coupled to an output of the charge amplifier, such that an effective capacitance of the first capacitor is increased based on a gain of the charge amplifier, wherein the first capacitor and an inverting input of the charge amplifier are further coupled to the first node.

2. The system according to claim 1 , wherein the inverting input of the charge amplifier is coupled to the first node via a second capacitor.

3. The system according to claim 1 , wherein a non-inverting input of the charge amplifier is coupled to a reference voltage.

4. The system according to claim 1 , wherein the capacitive circuitry further comprises a resistive element coupled between the output of the charge amplifier and the inverting input of the charge amplifier.

5. The system according to claim 1 , further comprising one or more switches operable to selectively couple and decouple the charge amplifier from the feedback loop.

6. The system according to claim 5 , wherein the one or more switches are operable to couple the charge amplifier to the feedback loop in a first mode of operation for measurement of a capacitance of the MEMS capacitive transducer.

7. The system according to claim 5 , wherein the one or more switches are operable to decouple the charge amplifier from the feedback loop in a second mode of operation of the system.

8. The system according to claim 1 , wherein the effective capacitance of the first capacitor is increased via the Miller effect.

9. The system according to claim 1 , wherein the biasing circuitry comprises a charge pump coupled to the first node.

10. The system according to claim 9 , wherein the biasing circuitry further comprises a filter arranged between the charge pump and the first node, for filtering high-frequency noise from the charge pump.

11. The system according to claim 1 , further comprising:
test circuitry coupled to the second node, operable to:
selectively apply one or more current sources to the second node, so as to charge and discharge the MEMS capacitive transducer and so vary a signal based on a voltage at said second node between an upper value and a lower value;
determine a parameter that is indicative of a time period of the variation of the signal; and
determine a capacitance of the MEMS capacitive transducer based on the parameter that is indicative of the time period.

12. The system according to claim 1 , embodied on a single integrated circuit.

13. An electronic device, comprising:
a system as claimed in claim 1 .

14. The electronic device according to claim 13 , wherein the electronic device is one of: a portable electronic device; a battery-powered electronic device; a mobile telephone; an audio player; a video player; a PDA; a wearable device; a mobile computing platform; a smartphone; a laptop computer; a tablet computer; a games device; a remote control device; a toy; a domestic appliance; a controller of a domestic appliance; a home audio system or device; a domestic temperature or lighting control system; a security system; and a robot.

15. A system, comprising:
a MEMS capacitive transducer, comprising one or more first capacitive plates coupled to a first node and one or more second capacitive plates coupled to a second node; and
capacitive circuitry coupled to the first node, comprising a charge amplifier and a first capacitor coupled to an output of the charge amplifier, and arranged such that an effective capacitance of the first capacitor is increased via the Miller effect based on a gain of the charge amplifier, wherein the first capacitor and an inverting input of the charge amplifier are coupled to the first node.

16. The system according to claim 15 , wherein the inverting input of the charge amplifier is coupled to the first node via a second capacitor.

17. The system according to claim 15 , wherein the capacitive circuitry further comprises a resistive element coupled between the output of the charge amplifier and the inverting input of the charge amplifier.

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Lasseuguette Jean Pierre
• KHENKIN Aleksey Sergeyevich
• Thomsen Axel

Classifications

• H04R19/04

  Microphones (H04R19/01 takes precedence) · CPC title

• H04R19/005

  using semiconductor materials · CPC title

• G01R27/26

  Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants {; Measuring impedance or related variables} · CPC title

• B81C99/003

  Characterising MEMS devices, e.g. measuring and identifying electrical or mechanical constants · CPC title

• H04R7/00

  Diaphragms for electromechanical transducers (in general F16J3/00); Cones (for musical instruments G10 ){(cones, diaphragms or the like, for emitting or receiving sound in general G10K13/00; Mounting thereof)} · CPC title