A 21.2μA -Based Interface ASIC for a Capacitive 3-Axis Micro-Accelerometer

In this paper, a micropower interface IC for a capacitive 3-axis micro-accelerometer implemented in a 0.25 -μm CMOS process is presented. The fully-integrated sensor interface consists of a sensor front-end that converts the acceleration signal into the digital domain, a decimator, a frequency reference, a clock generator for the front-end, a voltage and current reference, the required reference buffers, and low-dropout regulators (LDOs) needed for system-on-chip power management. The interface IC provides operating modes for 1 and 25Hz signal bandwidths. The chip with a 1.72mm active area draws 21.2μA in 1Hz mode, and 97.6μA in 25Hz mode, from a 1.2 2.75V supply. In 1Hz mode with a 2 -g capacitive 3axis accelerometer, the measured noise floors in the x-, y-, and z-directions are 1080, 1165 and 930μg/ Hz, respectively.