A closed-loop sigma-delta ('") capacitive microaccelerometer interface circuit is proposed in this work based on the time shared multiplexing electrostatic feedback and correlated-double-sampling (CDS) techniques. The noise analysis of the proposed low noise capacitance detection circuit is presented. The interface circuit is fabricated in a standard CMOS process and the active area is 13 mm 2 . The chip consumes 20 mW from a 5 V supply and the sampling frequency is 250 kHz. The measured results show that the sensor achieves a noise floor of 6 µg/Hz 1/2 in a closed-loop operation over a 1.5 kHz bandwidth, and the achieved figure of merit (FOM, 53 pW/Hz) is better than the previously reported '" interfaces.
A fifth-order fully differential interface circuit (IC) with onchip-test function is presented to improve the noise performance for micromechanical sigma-delta ('-") accelerometer. The proposed onchip-test technique for '-" accelerometers avoids a shaker table applying a sinusoidal signal as the simulated acceleration which involves distortion itself. An electrostatic force feedback linearization circuit is presented to reduce the harmonic distortion resulting in a larger dynamic range (DR). The post-simulation results show that the electrostatic force feedback linearization circuit decreases the harmonic distortion effectively and the proposed on-chip-test technique achieves 98 dB third-order harmonic distortion detection, and the nonlinearity of the proposed circuit is 0.02%.
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