Mode-tuning sense interface

Patent metadata

Field	Value
Publication number	US-10001387-B2
Application number	US-201615058084-A
Country	US
Kind code	B2
Filing date	Mar 1, 2016
Priority date	Dec 19, 2012
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A MEMS capacitive sensing interface includes a sense capacitor having a first terminal and a second terminal, and having associated therewith a first electrostatic force. Further included in the MEMS capacitive sensing interface is a feedback capacitor having a third terminal and a fourth terminal, the feedback capacitor having associated therewith a second electrostatic force. The second and the fourth terminals are coupled to a common mass, and a net electrostatic force includes the first and second electrostatic forces acting on the common mass. Further, a capacitance measurement circuit measures the sense capacitance and couples the first terminal and the third terminal. The capacitance measurement circuit, the sense capacitor, and the feedback capacitor define a feedback loop that substantially eliminates dependence of the net electrostatic force on a position of the common mass.

First claim

What we claim is:

1. A method of reducing electrostatic spring softening, comprising:
measuring a change in position of a mass subjected to a first force depending on the change in position,
applying a second force to the mass, the second force comprising a force proportional to the measured change in position, the constant of proportionality being selected so that the net force of the first and second forces has reduced dependence on the change in position.

2. The method of claim 1 , wherein the dependence on the change in position is substantially eliminated.

3. The method of claim 1 , wherein the first and second forces act in opposite directions on the mass.

4. The method of claim 1 , further comprising the step of applying a high-voltage bias to the mass.

5. The method of claim 1 , wherein the steps of measuring a change in position and applying a second force are time division multiplexed.

Assignees

• Invensense Inc

Inventors

• Cagdaser Baris
• Shaeffer Derek
• Seeger Joseph

Classifications

• G01R27/2605

  Measuring capacitance (capacitive sensors G01D5/24) · CPC title

• G01C25/00 Primary

  Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass (testing, calibrating or compensating compasses G01C17/38) · CPC title

• G01C19/5726 Primary

  Signal processing · CPC title

• G01D5/24

  by varying capacitance · CPC title