A navigation-grade MEMS accelerometer based on a versatile front end

Abstract

This paper presents a MEMS-based 5^th-order ΔΣ capacitive accelerometer. The ΔΣ loop is implemented in mixed signal, the global 5^th-order filter having a 2^nd-order analog and a 3^rd-order digital part. The system can be used with a wide range of sensors, because the mixed-signal front-end is programmable. The developed ASIC comprises a voltage-mode preamplifier, two parallel demodulators implementing CDS, and a 7-bit internally non-linear flash ADC. The latter drives a 3^rd-order digital filter which can be configured for different sensor parameters in order to ensure overall loop stability and to optimize the noise performance. With a low-noise MEMS sensor, the system achieves a 19-bit DR and a 16-bit SNR, both over a 300-Hz bandwidth.