A high-precision low-power capacitive sensor readout circuit

This paper presents a readout circuit for CMOSMEMS accelerometer sensors, including a current-to-voltage lownoise weak signal amplifier, a high-precision second-order singlebit quantization Sigma-Delta modulator and a digital filter. We analyse the main factors affecting the noise of the sample and hold circuit and ADC, and the methods to suppress noise and improve linearity. Meanwhile, we reduce power consumption by reducing the order of the modulator and designing it in discrete time when the accuracy could meet the specifications of the sensor header, and achieve monolithic integration of the accelerometer CMOSMEMS chip. Designedin TSMC 180 nm CMOS process, the proposed readout circuit achieve 16-bit high-precision effectivenumber-of-bits (ENOB) and 0.3 mW power consumption.