A 43nW 32kHz Pulsed Injection TCXO with 4.2ppm Accuracy Using ∆Σ Modulated Load Capacitance

Abstract

This paper presents an ultra-low power temperature-compensated crystal oscillator (TCXO) with a pulsed injection XO driver for IoT applications. Temperature compensation is achieved using a single switched load capacitance, modulated by a ∆ΣM. The ∆ΣM digitizes a piece-wise linear (PWL) approximation of the XO temperature dependence where a coarse 4-bit temperature sensor selects the PWL segment. The proposed 32.768kHz TCXO achieves an accuracy of ±4.2ppm from -20℃ to 85℃ with 3-point trimming and Allan deviation floor of 34 ppb while consuming 43nW.