An Automatic MEMS Gyroscope Mode Matching Circuit Based on Noise Observation

Abstract

The performance of microelectromechanical system (MEMS) gyroscopes can be significantly enhanced by matching the resonance frequencies of the drive and sense mechanical resonators. However, the precise control of the resonance frequency in a closed loop readout circuit is challenging. This brief presents an automatic detection and control circuit, which performs a background tuning of the MEMS element. The tuning method is based on the observation of noise at the output of a continuous time ${\Delta \Sigma }$ modulator readout circuit, so that no modification of the sense loop, such as additional input force generation is required. Parasitic modulation of the sensor’s zero rate output due to the mode matching loop is canceled by an additional offset compensation circuit. The system is validated on an FPGA connected to a MEMS gyroscope and an ASIC readout circuit. The digital mode matching circuit would consume a power of ${21}~{\mu }\text{W}$ on an area of 0.17 mm2 in a ${0.35}~{\mu } \text {m}$ CMOS technology.