A closed-loop readout interface for MEMS accelerometer with time-multiplexing electrostatic force feedback

Abstract

The noise and linearity performance of a MEMS accelerometer is a critical issue for land seismic acquisition applications. Incorporating closed-loop force feedback is an effective way to enhance those performances. However, additional electrode to exert the electrostatic force is typically not available and residue displacement of proof mass would introduce significant nonlinearity to the closed-loop transfer function, impairing the efficiency of the method. This paper proposes a switched-capacitor closed-loop readout interface for MEMS accelerometer which greatly alleviates those problem. First, the proposed system incorporates a time-multiplexing technique, thus the sensing and force feedback can be realized using the same electrode and get separated in time sequence. Furthermore, the cross-coupling of high-voltage feedback signal and weak sensing signal can be minimized. Second, a correlated double sampling (CDS) technique and a PID control mechanism is introduced in the loop. Thus, the two sources of residue displacement: interface mismatch and insufficient loop gain can be well-suppressed. The test results show that the proposed closed-loop MEMS accelerometer can achieve an SNR better than 120 dB, with an in-band noise spectral density lower than 500 ng/Hz[Formula: see text].