A digital readout interface for a surface micromachined MEMS accelerometer with a novel loop compensator

Abstract

This paper proposes a novel digital readout interface for capacitive MEMS accelerometer. The digitalization is fulfilled by incorporating a 1-bit [Formula: see text] (sigma-delta) modulator into the closed servo loop. It both realizes a direct digital output efficiently and linearizes the electrostatic feedback force. To maintain the stability and improve loop linearity, a discrete-time proportional integral and differential (PID) compensator is used. It improves the in-band gain, enhances quantization noise suppressing ability and maintain the high-frequency phase margin at the same time. Thus the linearity and noise performance are improved. The whole chip is fabricated using 0.35 [Formula: see text]m CMOS-BCD technology. Test results show that, the linearity is better than 0.1% and the noise floor is as low as 1 [Formula: see text]g/[Formula: see text].