A Sub-0.1°/h Bias-Instability Split-Mode MEMS Gyroscope With CMOS Readout Circuit

This paper describes a split-mode tuning fork MEMS gyroscope with CMOS readout circuit. The gyroscope achieves 0.008°/hangle random walk (ARW) and 0.08°/h bias instability (BI). The noise and phase requirements of the MEMS sensing element and the readout circuit are analyzed, from which the system-level design guidelines are proposed. The MEMS sensing element is optimized to enhance its mechanical sensitivity with reduced quadrature coupling and thermoelastic damping. Front ends with 5.9-fA/Hz input-referred current noise floor and less than 0.5° phase delay are achieved to reduce the gyroscope’s ARW and thermal drift. A low flicker noise automatic amplitude control circuit and digitized phase-sensitive demodulation are adopted to improve the gyroscope’s BI. After temperature compensation, the temperature coefficients (TCOs) of the scale factor and the zero-rate output are 27 ppm/°C and 1.7°/h/°C from −40 °C to +60 °C, respectively. The overall power consumption is 8.5 mW under a 3.3-V supply.