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This paper presents the design and implementation of a high-order ΣΔ interface for micromachined inertial sensors, which employs an electronic filter in series with the mechanical sensor element to reject the excessive in-band quantization noise inherently present in state-of-the-art second-order solutions. A fourth-order prototype was fabricated in a standard 0.5-μm CMOS process. The active circuit area measures 0.9 mm2, and the interface consumes 13 mW from a 5-V supply and achieves resolution of 1°/s/√Hz with a gyroscope and 150μg/√Hz with an accelerometer. Comparison between the measured and simulated behavior of the system shows that the contribution of the quantization error to the total noise is negligible.
Date of Publication: Aug. 2005