Research on nonlinearity of closed-loop capacitive accelerometer resulting from time-division force feedback

Linearity which determines the system precision is one of the main performance parameters of accelerometers especially the wide-range ones. The design parameters of the interface circuit have a great effect on the linearity of the accelerometer system utilizing time-division force feedback (TDFF). In this paper, the nonlinearity resulting from time-division force feedback is discussed and the formulae reflecting the relationship between the system linearity and the design parameters are derived, which can help the designers to adjust timing parameters according to the linearity demand. The theory is verified by Matlab/Simulink numerical simulation. Based on the design formulae presented, a ±30 g closed-loop TDFF capacitive micro-accelerometer is implemented in 0.35 μm high-voltage CMOS process, which operates under ±6.5 V supply and achieves linearity of 99.72% in the self-test mode.