A Sub-0.2 $^{\circ}/$ hr Bias Drift Micromechanical Silicon Gyroscope With Automatic CMOS Mode-Matching

This paper describes a system architecture and CMOS implementation that leverages the inherently high mechanical quality factor (Q) of a MEMS gyroscope to improve performance. The proposed time domain scheme utilizes the often-ignored residual quadrature error in a gyroscope to achieve, and maintain, perfect mode-matching (i.e., ~ 0 Hz split between the high-Q drive and sense mode frequencies), as well as electronically control the sensor bandwidth. A CMOS IC and control algorithm have been interfaced with a 60 mum thick silicon mode-matched tuning fork gyroscope (M²-mathchar TFG) to implement an angular rate sensing microsystem with a bias drift of 0.16deg/hr. The proposed technique allows microsystem reconfigurability-the sensor can be operated in a conventional low-pass mode for larger bandwidth, or in matched mode for low-noise. The maximum achieved sensor Q is 36,000 and the bandwidth of the microsensor can be varied between 1 to 10 Hz by electronic control of the mechanical frequencies. The maximum scale factor of the gyroscope is 88 mV/deg/s . The 3 V IC is fabricated in a standard 0.6 mum CMOS process and consumes 6 mW of power with a die area of 2.25 mm².