Automatic Compensation of Parallel Capacitance of TPoS MEMS Resonator for Accurate Frequency Tracking with PLL-Based Oscillator Circuit

This paper proposes an oscillator circuit based on a phase-locked loop which automatically compensates for the parasitic capacitance of Thin-film Piezoelectric-on-Silicon (TPoS) contour-mode resonators. The circuit enables accurate tracking of the mechanical parameters of the resonators in demanding sensor applications by advantageously combining their favorable Q-factor with the electrical resonance enhancement arising from the automatic cancellation of parallel capacitance. Preliminary results on tracking the resonant frequency of a TPoS resonator due to temperature variations show a temperature coefficient of frequency of 53.4 ppm/°C.