Temperature compensation of a capacitive MEMS accelerometer by using a MEMS oscillator

摘要

This study reports a temperature compensation method for a capacitive MEMS accelerometer by using a MEMS double-ended-tuning-fork (DETF) resonator integrated with the accelerometer structure on the same die. The proposed method utilizes the frequency information of the clamped-clamped DETF resonator which is oscillating in a closed-loop operation. In order to compensate the temperature dependence of the accelerometer output, frequency drift of the DETF resonator against changing temperature is used, i.e., the resonator frequency is used as the temperature data for compensation purposes. On-chip integration of two sensors allows precise temperature sensing abilities by removing the thermal lag between the DETF resonator and the accelerometer. Tests are held in the -20 °C and 60 °C range by operating both sensors simultaneously in a temperature-controlled oven. The measurement results indicate temperature coefficient of frequency (TCf) of 480 ppm/K for the integrated resonator and temperature dependence of 1,164 μg/K for the accelerometer output, which is decreased to 1.4 μg /K after temperature compensation. Improved noise performances indicate the bias instability of 30 μg and the velocity random walk of 24 μg/sqrt(Hz) with the removal of the temperature ramp (after 30 seconds) in Allan-deviation plot.