Solving FSR Versus Offset-Drift Trade-Offs With Three-Axis Time-Switched FM MEMS Accelerometer

Abstract

This paper describes the working principle, the design, and the characterization of a three-axis frequency-modulated MEMS accelerometer, in which the differential frequency readout is performed through a novel time-switched approach. The proposed methodology is based on a double sampling of the oscillation frequency of a single resonator, consecutively biased in two different configurations in time. This technique enables to avoid offset thermal drift contributions typical of differential resonant accelerometers based on two distinct resonators with unavoidable mismatch in the temperature coefficient of frequency (TCf). Alternatively, a residual TCf offset drift component can be tuned to counterbalance other drift sources (e.g., stress-related), allowing a complete cancellation of the zero-g-offset (ZGO) thermal drift. Experiments on various samples report repeatable sub- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\mu \text{g}$ </tex-math> </inline-formula> /K thermal drift without post-acquisition corrections, with a full-scale higher than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$32~g$ </tex-math> </inline-formula> at a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$100~\mu \text{g}/\sqrt {\text {Hz}}$ </tex-math> </inline-formula> consumer-grade resolution. [2018-0089]