An effective temperature compensation algorithm for CMOS-MEMS thermal-piezoresistive oscillators with SUB PPM/°C thermal stability

A real-time temperature compensation method using resistance control with two-point calibration, implemented in a CMOS-MEMS thermal-piezoresistive oscillator (TPO), has been demonstrated in this work. To enhance the thermal stability of the CMOS-MEMS TPO for future mass/aerosol sensing applications, a novel algorithm is proposed to attain a temperature coefficient of frequency (TCF) of only -0.5 ppm/°C which is 66 times improvement over uncompensated case. The implemented TPO has no passive compensation as the structure is made of CMOS back end oxide and polysilicon to obtain a high quality factor (Q) of 2,000 in air. The heater resistance serves as ambient temperature sensor. As a result, the proposed method only requires measurement at two temperature points to modify the controlled resistance of the heater and is much more convenient than other low TCF methods utilizing look-up table (LUT) or polynomial equation fit.