Design analysis of a high-Q micromechanical capacitive accelerometer system

Abstract

A micromechanical capacitive accelerometer system is analyzed in this paper, which includes a high-Q sensing element and a high-order switched-capacitor (SC) sigma-delta ΣΔ CMOS interface circuit. The high-Q high-order topology obtained a sub-µg/√Hz noise floor. The loop stability is implemented by the operation of electrostatic feedback force, heavy phase compensation and the off-chip adjusting of distributed-feedback factors. The interface circuit is implemented in a standard 0.5 µm CMOS process. The system consumes 12 mW from a single 5 V supply with the noise level of lower than 400 ng/√Hz. The system bandwidth is 600 Hz and the input range of the accelerometer is ±0.7 g. The measured sensitivity of 2.5 V/g is achieved.