A three-axis micromachined accelerometer with a CMOS position-sense interface and digital offset-trim electronics

This paper describes a three-axis accelerometer implemented in a surface-micromachining technology with integrated CMOS. The accelerometer measures changes in a capacitive half-bridge to detect deflections of a proof mass, which result from acceleration input. The half-bridge is connected to a fully differential position-sense interface, the output of which is used for one-bit force feedback. By enclosing the proof mass in a one-bit feedback loop, simultaneous force balancing and analog-to-digital conversion are achieved. On-chip digital offset-trim electronics enable compensation of random offset in the electronic interface. Analytical performance calculations are shown to accurately model device behavior. The fabricated single-chip accelerometer measures 4 x 4 mm(2), draws 27 mA from a 5-V supply, and has a dynamic range of 84, 81, and 70 dB along the x-, y, and z-axes, respectively.