A Sub-µg Bias-Instability MEMS Oscillating Accelerometer With an Ultra-Low-Noise Read-Out Circuit in CMOS

• Published in: IEEE journal of solid-state circuits 2015-09, Vol.50 (9), p.2113-2126
• Main Authors: Zhao, Yang, Zhao, Jian, Wang, Xi, Xia, Guo Ming, Qiu, An Ping, Su, Yan, Xu, Yong Ping
• Format: Article
• Language: English
• Subjects: Accelerometers; Amplitude control; bias-instability; Circuit stability; continuous-time; MEMS resonator; Micromechanical devices; Noise; noise floor; oscillating accelerometer; Oscillators; Resonant frequency; Sensors; transimpedance amplifier
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2015.2431076

This paper describes a SOI MEMS oscillating accelerometer with a fully differential CMOS continuous-time read-out circuit. A new ultra-low-noise continuous-time bandpass transimpedance amplifier (TIA) is proposed and serves as the front-end of the read-out circuit. The new TIA topology greatly relaxes the tradeoffs among gain, bandwidth and noise, and achieves a state-of-the-art input referred current noise density of 6.6 fA/√Hz, which helps improve the bias-instability and noise floor of the MEMS oscillating accelerometer. The TIA provides a transimpedance gain of 45 MΩ in the bandwidth from 0.5 Hz to 350 kHz and consumes only 583 μW. To reduce the amplitude-stiffness effect induced frequency variation, the accelerometer employs a displacement control strategy that stabilizes the oscillation amplitude of the MEMS oscillator and a chopper stabilization technique to minimize the flicker noise in the amplitude control block. The accelerometer yields bias-instability of 0.6 μg (Allan Variance) or bias stability of 6.3 μg (1σ in one hour) and 2 μg/√Hz noise floor with 140 Hz/g scale factor and ±20 g full scale. The overall power consumption of the accelerometer is 3.5 mW under a 1.5 V supply.