A Mode-Matching ΔΣ Closed-Loop Vibratory-Gyroscope Readout Interface with a 0.004°/s/√Hz Noise Floor over a 50Hz Band

As micromachined vibratory gyroscopes push to lower noise floors, mode matching is necessary to moderate interface power dissipation. Mode matching increases sense displacements by the sense mode quality factor and thereby relaxes the precision requirements of the front-end, but also creates several difficulties as evidenced in a recent work [1]. Because it uses mode matching with open-loop sensing, the system in [1] has a bandwidth of less than 1Hz and is susceptible to substantial scale factor variation and phase uncertainty induced by variations of the Q and resonance frequency with PVT. Our design overcomes these limitations by using force feedback to achieve a stable scale factor, a well defined phase relationship, and a bandwidth well in excess of 50Hz, commensurate with the requirements of automotive and consumer applications. This paper describes the architecture and circuits used to exploit mode matching effectively to attain order-of-magnitude noise and power dissipation reductions over state-of-the-art implementations without sacrificing other aspects of system performance.