Design of digital closed-loop monolithic integrated ASIC interface circuit for MEMS gyroscope

In order to improve the linearity and stability of MEMS gyroscope, a digital dual closed loop interface circuit for capacitive MEMS gyroscope is designed. Firstly, the system structure is summarized, including C/V conversion circuit, high precision ADC, digital signal processing module and so on. Then the drive closed-loop control system based on automatic gain control (AGC) is designed, and the loop stability conditions are analyzed for the quick commissioning of the drive closed-loop system. Finally a force-feedback architecture based on fourth-order electromechanical sigma delta modulator (EM-ΣΔM) for gyroscope sense mode is proposed. The interface circuit is implemented in 0.18 μm HVCMOS technology, and the ASIC is bonded in one package with the gyroscope structure for a better performance. Measurement results indicate the superior performance of the gyroscope, with a bias instability of 0.58 °/h, a angular random walk of 0.07°/√h, and a nonlinearity of 52.8 ppm under a full-scale range of ±500 °/s, which meets the application requirements of high-performance MEMS gyroscopes. © 2020, Editorial Department of Journal of Chinese Inertial Technology. All right reserved.