A charge balancing accelerometer interface with electrostatic damping

This paper presents a switched capacitor accelerometer sensor interface. Self-balancing bridge topology, which has ratiometric output, is used for signal detection. In order to damp the high quality factor of a micro-mechanical sensor element, a force-feedback with a proportional-derivative controller is combined with the open-loop topology. The controller doesn´t affect the low-frequency properties of the open-loop readout. A 2^nd-order single-bit ΔΣ converter is used for analog-to-digital conversion. The interface is implemented in a 0.35 μm CMOS process and the area of the accelerometer chip is 6.66 mm². The nominal supply voltage is 3.6 V and the current consumption 1 mA. The interface achieves maximum dc nonlinearity of 0.18 % with an input range of ± 1.15 g. The SNR of the interface is 91 dB with a signal bandwidth of 200 Hz.