Low-Noise Readout Circuit for an Automotive MEMS Accelerometer

Abstract

This paper presents a charge-balanced readout circuit for MEMS capacitive accelerometers. The focus of this work is a design with a low-noise and low area consumption while ensuring the essential linearity and electromagnetic compatibility (EMC) for automotive applications. The readout circuit is composed of a charge-balanced single-ended input C/V stage followed by a second order sigma-delta modulator. The C/V stage uses a Gm stage combined with an integrator to reduce its noise contribution. The measurement results of the readout circuit show a noise floor of 62 $\mu g/{\sqrt {\mathrm{ Hz}}}$ and a temperature dependent offset smaller than ±0.6 mg after compensation. The measured dynamic range of the complete interface, including readout circuit and sensor, is 95.5 dB. The measured EMC is below 2 mg. The accelerometer readout circuit has been designed in a 130nm technology. Its power and area consumption is 1.4 mW and 0.26mm2.