118-dB dynamic range, continuous-time, opened-loop capactance to voltage converter readout for capacitive MEMS accelerometer

Abstract

A high performance analog front-end (AFE) interface circuit for capacitive MEMS accelerometer is presented in this paper. The AFE was implemented in a continuous-time (CT), chopper stabilized, capacitance to voltage converter (CVC) topology with a variable gain amplifier (VGA) for greater flexibility and a low pass filter (LPF) which limited the signal bandwidth to 300 Hz. Noise analysis of each building block of the AFE is also presented in this paper. The measured input referred noise density is 27 nV/√Hz. Long term stability results showed that the input offset has an Allan deviation floor of 60 nV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> . The nonlinearity for the AFE was measured at ± 1 %.