Role of Feedthrough Capacitance in Mode-Split MEMS Gyroscope Bias-Instability

MEMS gyroscopes play a crucial role in navigation and stabilization tasks across both consumer and high-end markets. To meet the requirements of these applications, the system must maintain the output stability under external perturbations, like temperature and stress, while minimizing calibration and design costs. In this paper, we investigate the drive loop feedthrough capacitance impact on the system bias instability. Notably, we find that even an aF feedthrough variation forces the drift of the drive oscillation frequency and the change of the optimal demodulation phase. The consequence is a variation of the measured output or, in other words, a non-negligible bias instability contribution. To support our findings, we develop a mathematical model and conduct relative simulations in a controlled Simulink environment. The evaluation matches with Allan variance simulation and with preliminary experiment. By shedding light on the origins of feedthrough contribution, our research lays the groundwork for more precise strategies for bias instability compensation and for discussing other potential sources.