A CMOS switched-capacitor interface circuit for an integrated accelerometer

Abstract

Presents a CMOS interface electronics for monolithic micromachined capacitive accelerometer systems. The interface electronics is a fully differential switched-capacitor charge integrator with its internal clock generator and sensor feedback circuit for closed-loop operation. The circuit is designed for open-loop and closed-loop operations, and provides both digital and differential analog outputs. One of the main advantages of this chip is that it can be monolithically integrated with the sensor, resulting in a considerably increased sensor module performance by decreasing the overall system area, minimizing the interface parasitics, and simplifying the packaging. The interface electronics operates at 200kHz sampling clock and provides an adjustable sensitivity between 0.3 and 1.2V/pF with better than 100aF expected resolution resulting in a 93dB dynamic range for 1Hz bandwidth. The total chip dissipates less than 7.2mW power from a single 5V supply, and occupies an area of 3.4/spl times/3.6 mm/sup 2/ in 3/spl mu/m one-metal two-poly p-well. CMOS process of University of Michigan.