A low-noise fully-differential open-loop interface for high-G capacitive micro-accelerometers with 112.2 dB dynamic range
A fully-differential open-loop switched capacitor interface is presented in this paper for a ±30 g capacitive micro-accelerometer. Considering that input common-mode feedback capacitors in a fully-differential charge sensitive amplifier increase the gain of noise, a full-swing input common-mode feedback scheme is proposed in this work to minimize the feedback capacitance and reduce the noise. Moreover, since flicker noise contributed by the output stage cannot be ignored in an ultra low-noise design, a novel low-noise fully-differential sample- and-hold circuit is proposed, which not only suppresses the flicker noise considerably but also has smaller output spikes with lower power dissipation. The interface implemented in a 0.35 μm CMOS process occupies 9 mm2 and consumes 8.11 mA from a 3.3-V supply at a sampling clock of 1 MHz. The sensor achieves 80.4 mV/g sensitivity, 10 μg/√Hz resolution and 112.2 dB dynamic range over a signal bandwidth of 200 Hz.