A MEMS microphone interface based on a CMOS LC oscillator and a digital sigma-delta modulator

Capacitive or resistive sensors can be included in the feedback network of an oscillator to implement a data acquisition system. A higher sampling rate, compared with standard oversampled converters, is required to maintain a sufficient SNR in this case. In this paper, we propose an architecture based on a LC-CMOS oscillator and a digital interface that can be completely integrated on chip and satisfies low clock specifications of standard microphone capacitive interfaces. The complete system outputs one-bit bitstream at 15.53MHz and achieves SNR of 55.38dB for -26dBfs input tone.