A low-noise closed-loop interface for high-G capacitive micro-accelerometer
A switched capacitor interface is presented in this paper for a ±50 g capacitive micro-accelerometer. In order to suppress the flicker noise of the frontend, a switched capacitor proportional-integral controller combined with a charge sensitive amplifier using correlated double sampling is proposed. The controller has a simple structure with minimized number of switches and cancels the offset of both the charge sensitive amplifier and itself. A delay buffer following the controller is used to generate a z-1/2 delay and drive the middle plate of the sensing element. The interface is implemented in a 0.35 μm 3.3 V/15 V CMOS process and the area of the chip is 11.75 mm2. The fabricated prototype circuit operates under 15 V and 3.3 V supply at a sampling clock of 100 kHz. Meanwhile, a sensitivity of 99.7 mV/g is achieved with the bias instability of 200 μg. The dynamic range of the accelerometer is 106.16 dB over a signal bandwidth of 200 Hz.