Abstract
This work presents a power-efficient differential readout interface with digital output and negative force-feedback for capacitive MEMS accelerometers. The readout interface is designed for the monolithically integrated MEMS accelerometer embedded in the same CMOS die; however, it can also be used for external sensors for structural health monitoring applications. The readout interface is fabricated using a 0.18 µm CMOS 1P6M process with effective dimensions of 200 µm × 200 µm along with on-chip voltage/current biases and a digital controller. The electrical measurement results demonstrate a configurable readout sensitivity of 160 mV/g to 1.12 V/g with a noise floor of 100nV/√(Hz) equivalent to 350 µg/√(Hz). The measured dynamic range is 72 dB (1 mg to 4 g) and the peak SNDR of 66 dB is achieved for an input of 2 g. The readout interface has been tested and characterized with an external tri-axial accelerometer ADXL335 inside the lab using an electromagnetic vibrator and also in the field for pipeline leakage detection scenarios using the acceleration-gradient technique. The measured in-lab acceleration testing exhibits a 99% normalized matching with the electrical testing, establishing feasibility through extrapolation of the measurement results with an external sensor, of the readout interface for high-sensitivity on-chip and off-chip MEMS accelerometer sensors.