A Temperature-Drift Suppression Phase-Locked-Loop With Tunable Locked Range and Frequency Division for MEMS Resonant Accelerometers

MEMS resonant accelerometers have attracted attention because of their high resolution and quasi-digital output, but their performances are seriously damaged by external temperature fluctuations. Our previous work proposed a Temperature-Drift Suppression Phase-Locked-Loop featuring a temperature-sensitive resonator (TSR) as a voltage-controlled oscillator to monitor the frequency variations of the accelerometer-sensitive resonator (ASR). To solve the problem of mismatched temperature coefficients between the TSR and ASR, the frequency synthesis unit is introduced in this paper. The temperature drift of the two resonators can offset each other by adjusting the division factor so that the acceleration drift caused by temperature can be mitigated. Additionally, the proposed SAFR algorithm automatically adjusts the locked range of the PLL, thereby expanding the full-scale range of the accelerometer. The effectiveness of the system is further validated through theoretical analysis and simulations. Experimental results indicate that the bias-instability is 3.7μg and the noise floor is 1.24μg/√Hz with ±2g full-scale range at room temperature. The temperature drift is 54mg within a temperature range of 10°C to 60°C which is reduced by 95% compared to the uncompressed MRA (1.23g).