A closed-loop interface for capacitive micro-accelerometers with pulse-width-modulation force feedback

摘要

This paper presents an electromechanical closed-loop interface for the high performance capacitive micro-accelerometer. To overcome the problem that the linearity of the traditional analogue force feedback scheme is sensitive to the mismatch in the MEMS transducer, a pulse-width-modulation (PWM) force feedback method is developed in this paper. Elaborate non-linearity analysis of the PWM force feedback and a comparison with traditional analog feedback method is presented. A prototype interface circuit is designed and fabricated in a standard 0.35 mu m CMOS process which measures 6.25 mm(2). The noise floor of the system is 10 mu g/root Hz and the signal bandwidth is 1.2 kHz, respectively. The system shows a DC nonlinearity of 1.6% without extra linearization circuit with an input range of +/- 1.4 g when interface to a commercial accelerometer device.