Multi-mode sigma-delta ADC circuit and microphone circuit having a multi-mode sigma-delta ADC circuit

A multi-mode sigma-delta analog-to-digital converter (ADC) circuit, the multi-mode sigma-delta ADC circuit comprising:

• a pair of operational transconductance amplifiers (OTAs);
• a filter connected to the pair of OTAs;
• a quantizer connected to the filter;
• a differential digital-to-analog converter (DAC) connected to the quantizer, wherein the DAC comprises a plurality of resistors and a plurality of switches connected to the resistors, wherein an output of a microphone and a differential output of the differential DAC are inputted into a plurality of input terminals of the pair of OTAs;
• and
• a controller configured to switch the multi-mode sigma-delta ADC circuit between a single-ended operational mode, a pseudo differential operational mode, and a full differential operational mode to improve common mode rejection (CMR) performance by controlling the pair of OTAs.

A microphone circuit, the microphone circuit comprising:

• a microphone;
• and
• a multi-mode sigma-delta analog-to-digital converter (ADC) circuit connected to the microphone, the multi-mode sigma-delta ADC circuit comprising:
• a pair of operational transconductance amplifiers (OTAs);
• a filter connected to the pair of OTAs;
• a quantizer connected to the filter;
• a differential digital-to-analog converter (DAC) connected to the quantizer, wherein an output of the microphone and a differential output of the differential DAC are inputted into a plurality of input terminals of the pair of OTAs;
• and
• a controller configured to switch the multi-mode sigma-delta ADC circuit between a single-ended operational mode, a pseudo differential operational mode, and a full differential operational mode to improve common mode rejection (CMR) performance by controlling the pair of OTAs.