US 9,813,831 B1
Microelectromechanical systems microphone with electrostatic force feedback to measure sound pressure
Axel Thomsen, Austin, TX (US)
Assigned to Cirrus Logic, Inc., Austin, TX (US)
Filed by Cirrus Logic International Semiconductor Ltd., Edinburgh (GB)
Filed on Nov. 29, 2016, as Appl. No. 15/363,863.
Int. Cl. H04R 29/00 (2006.01); H04R 19/04 (2006.01); H04R 19/00 (2006.01)
CPC H04R 29/004 (2013.01) [H04R 19/005 (2013.01); H04R 19/04 (2013.01); H04R 2201/003 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A microelectromechanical systems microphone, comprising:
a backplate comprising a first plurality of electrodes comprising at least a first electrode and a second electrode electrically isolated from one another and each is mechanically coupled to the backplate in a fixed relationship relative to the backplate; and
a diaphragm configured to mechanically displace relative to the backplate as a function of sound pressure incident upon the diaphragm, wherein the diaphragm comprises a second plurality of electrodes, the second plurality of electrodes comprising at least a third electrode and a fourth electrode, wherein the third electrode and the fourth electrode are electrically isolated from one another and each is mechanically coupled to the diaphragm in a fixed relationship relative to the diaphragm such that the second plurality of electrodes mechanically displaces relative to the backplate as the function of sound pressure incident upon the diaphragm;
wherein:
the first electrode and the third electrode form a first capacitor having a first capacitance;
the second electrode and the fourth electrode form a second capacitor having a second capacitance; and
the first capacitor is configured to sense a mechanical displacement of the diaphragm responsive to which the second capacitor is configured to apply an electrostatic force to the diaphragm to return the diaphragm to an original position.