A Time-Domain Accuracy-Boosted Temperature Compensated Crystal Oscillator

This article presents a megahertz temperature compensated crystal oscillator (TCXO) featuring a time-domain accuracy boosting scheme to enhance the signal-to-noise and distortion ratio (SNDR) at the oscillator core’s tuning port. The proposed TCXO employs three key techniques: a time-domain architecture that progressively shapes and suppresses offsets in the sensed temperature and applied compensation, an enhanced-decimation filter implementation to eliminate noise from the temperature front end, and a low-noise, high-linearity load capacitance tuning interface to minimize phase noise (PN) and spurs. Implemented in a 0.18- $\mu $ m CMOS process, the TCXO achieves ±0.6 ppm/±1.4 ppm frequency accuracy over ${-} 55~{^{\circ }}$ C to $85~{^{\circ }}$ C/ $115~{^{\circ }}$ C, corresponding to a $38.6{\times }$ / $13.2{\times }$ improvement over uncompensated cases while maintaining competitive noise performance compared with existing solutions.