Independently charge pumps for differential microphone

Abstract

Systems and methods of generating independent adjustable bias voltages for a differential microphone. The microphone system includes a positive adjustable charge pump, a positive sense capacitor, a negative adjustable charge pump, a negative sense-capacitor, and a differential amplifier. The positive adjustable charge pump is configured to generate a positive bias voltage. The positive sense-capacitor is configured to generate a positive sense voltage based on acoustic pressure from a first direction and the positive bias voltage. The negative adjustable charge pump is configured to generate a negative bias voltage. The negative sense-capacitor is configured to generate a negative sense voltage based on the acoustic pressure from the first direction and the negative bias voltage. The differential amplifier is configured to receive the positive and negative sense voltages. The differential amplifier is also configured to generate a differential voltage based on the positive and negative sense voltages.

What is claimed is: 
     
         1 . A microphone system comprising:
 a differential amplifier;   a positive adjustable charge pump configured to generate a positive bias voltage;   a positive sense-capacitor coupled to a first terminal of the differential amplifier and configured to
 receive acoustic pressure from a first direction, 
 receive the positive bias voltage, and 
 generate a positive sense voltage based on the acoustic pressure and the positive bias voltage; 
   a negative adjustable charge pump configured to generate a negative bias voltage having a magnitude different than a magnitude of the positive bias voltage;   a negative sense-capacitor coupled to a second terminal of the differential amplifier and configured to
 receive the acoustic pressure from the first direction, 
 receive the negative bias voltage, and 
 generate a negative sense voltage based on the acoustic pressure and the negative bias voltage; 
   a first high-impedance device coupled between the first terminal and a reference node; and   a second high-impedance device coupled between the second terminal and the reference node;   wherein the differential amplifier is configured to
 receive the positive sense voltage, 
 receive the negative sense voltage, and 
 generate a differential voltage based on the positive sense voltage and the negative sense voltage. 
   
     
     
         2 . The microphone system according to  claim 1 , wherein the positive adjustable charge pump is further configured to adjust the positive bias voltage by adjusting the first frequency, wherein the negative adjustable charge pump is further configured to adjust the negative bias voltage by adjusting the second frequency. 
     
     
         3 . The microphone system according to  claim 1 , wherein the positive adjustable charge pump further includes a positive voltage regulator configured to generate the positive reference voltage, wherein the negative adjustable charge pump further includes a negative voltage regulator configured to generate the negative reference voltage. 
     
     
         4 . The microphone system according to  claim 3 , wherein the positive adjustable charge pump is further configured to adjust the positive bias voltage by adjusting the positive reference voltage, wherein the negative adjustable charge pump is further configured to adjust the negative bias voltage by adjusting the negative reference voltage. 
     
     
         5 . A method of generating independent adjustable bias voltages for a differential microphone, the method comprising:
 adjusting a first frequency in which the positive reference voltage is applied to a plurality of positive stages in the positive adjustable charge pump to generate a positive bias voltage;   applying the positive bias voltage to a positive sense-capacitor coupled to a first terminal of the differential amplifier;   generating, via the positive sense-capacitor, a positive sense voltage based on the positive bias voltage and acoustic pressure from a first direction;   adjusting a second frequency in which the negative reference voltage is applied to a plurality of negative stages in the negative adjustable charge pump to generate a negative bias voltage, the negative bias voltage having a magnitude different than a magnitude of the positive bias voltage;   applying the negative bias voltage to a negative sense-capacitor;   generating, via the negative sense-capacitor, a negative sense voltage based on the negative bias voltage and the acoustic pressure from the first direction; and   generating, via a differential amplifier, a differential voltage based on the positive sense voltage and the negative sense voltage.