Automatic feedthrough cancellation methods for MEMS gyroscopes

Abstract

The feedthrough effect can significantly affect the performance of MEMS gyroscopes and even lead to device failure. In order to address the inevitable problem of feedthrough capacitance caused by microfabrication process and circuit structure, two automatic feedthrough cancellation solutions are proposed based on the analysis of the feedthrough effect. Firstly, an equivalent feedthrough model is established for MEMS gyroscopes. Then, through theoretical derivation and model simulation, various influences of feedthrough effect are analysed, and the critical value of feedthrough capacitance is calculated to achieve better compensation effects. For feedthrough capacitance greater than the critical value, a feedthrough cancellation method utilizing AD5231 digital potentiometer for generating an inverse signal is designed. For the situation of feedthrough capacitance less than the critical value, a feedthrough cancellation method based on pure digital circuit calculation is proposed. The experimental results show that the method of utilizing digital potentiometer effectively reduces the feedthrough level from −17.46 dB to −32.75 dB, and the method of utilizing pure digital circuit calculation compensates the feedthrough signal of 100.04 mV to almost zero (2.44 mV) within the range of ADC sampling accuracy. These two methods can accurately and quickly suppress feedthrough signal to improve the detection performance of MEMS gyroscopes, and are expected to meet the needs of future mass production. In addition, they can be widely applied to various MEMS devices that require feedthrough cancellation.