A digital MEMS gyroscope with 40°/h instability variation in -40° C to 85° C

This paper presents a digital MEMS gyroscope with 40°/h instability variation in -40°C to 85°C, performing 5°/h instability variation at normal temperature and 0.01% nonlinearity in the range of ±400°/s. This stability was achieved by using temperature compensation for the zero-output value changed after the temperature signal. As the resonant frequency of the mechanical structure varied according to the temperature linearly, a frequency calculator was adopted to detect the temperature of the mechanical structure. And the resolution of the frequency could be up to 0.01 Hz with a 1 MHz clock frequency used, obtaining a 10 Hz bandwidth. The driving mode used a PI controller to control a VGA to maintain at a fixed effective value of the driving signal. The sensing mode contained a low noise C/V convertor and a switch demodulation, which could give the angular velocity signal to the A/D convertor. Then the output data of A/D will be compensated in the digital domain. Finally, the digital output of the gyroscope will be available through a normal SPI serial port. The whole circuit was realized on one chip with an active circuit area of 3.5 mm × 5.2 mm fabricated in a 0.35 μm CMOS technology. And the MEMS structure and circuit are packaged in a 2.5 cm × 2.5 cm × 2.5 cm aluminum mold. The digital output of the gyroscope earned a noise floor of 0.0024°/s.