A fourth order unconstrained ΣΔ capacitive accelerometer

This paper reports the implementation of a high resolution and high dynamic range ΣΔ capacitive accelerometer for navigation applications. Designed system can achieve up to ± 40g full scale range, 131.9 dB dynamic range at 1 Hz, minimum noise floor of 6 μg/√Hz, and bias instability of 6.4μg. Flexible architecture combines the advantages of 2^nd and 4^th order ΣΔ modulators into a high performance design eliminating the stability dependence of high order accelerometers on fabrication variations. Due to high voltage pulse feedback technique and safe high order modulation; the designed accelerometer system achieves a respectable dynamic range without significantly increasing process, circuit or integration complexity.