Full-digital output ASIC for Lissajous Frequency Modulated MEMS Gyroscopes

The growing interest towards innovative working principles for microelectromechanical system (MEMS) based gyroscopes requires the development of new integrated circuit solutions that preserve their inherent long-term stability and short-term noise properties. This work presents the first mixed-signal, full-digital output application-specific integrated circuit (ASIC) for Lissajous frequency modulated (FM) gyroscopes, an operation mode in which the angular rate content to measure is first transduced into a dual frequency information, and then is further modulated in amplitude (in a sort of continuous mode-reversal) to bypass temperature related drifts of the frequency. The ASIC includes the core analog oscillators, two frequency-to-digital converters, a novel concept for the extraction of the demodulation reference which avoids phase lags, otherwise detrimental for stability performance, and the entire digital processing section including AM demodulators of both frequencies, their filtering, resampling and combination for a serial fully digital output. The ASIC is finally coupled to a MEMS gyroscope and its operation is demonstrated.