A 300Hz 19b DR capacitive accelerometer based on a versatile front end in a 5th-order ΔΣ loop

Abstract

This paper presents a 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 ASIC developed comprises a voltage-mode preamplifier, two parallel demodulators implementing CDS, and a 7-bit 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 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 300Hz bandwidth.