Abstract
A closed-loop sigma-delta (ΣΔ) capacitive microaccelerometer interface circuit is proposed in this work based on the time shared multiplexing electrostatic feedback and correlated-double-sampling (CDS) techniques. The noise analysis of the proposed low noise capacitance detection circuit is presented. The interface circuit is fabricated in a standard CMOS process and the active area is 13 mm2. The chip consumes 20 mW from a 5 V supply and the sampling frequency is 250 kHz. The measured results show that the sensor achieves a noise floor of 6 µg/Hz1/2 in a closed-loop operation over a 1.5 kHz bandwidth, and the achieved figure of merit (FOM, 53 pW/Hz) is better than the previously reported ΣΔ interfaces.
