Abstract:
This article describes an ultralow-power (ULP) temperature-compensated crystal oscillator (TCXO) with a pulsed-injection XO driver for IoT applications. Temperature compe...Show MoreMetadata
Abstract:
This article describes an ultralow-power (ULP) temperature-compensated crystal oscillator (TCXO) with a pulsed-injection XO driver for IoT applications. Temperature compensation is achieved by changing the load capacitance ( {C}_{L} ) between two values using a delta-sigma modulator ( \Delta \Sigma \text{M} ). The complex modulation profile across temperature is approximated as piecewise linear elements that is selected by a coarse temperature sensor. As a result, the power and area of fine-grain look-up tables (LUTs) or a polynomial engine used in prior works can be avoided. The proposed pulsed-injection XO driver that directly replenishes the energy of the {C}_{L} sustains the XO oscillation for the two different {C}_{L} states. Implemented in 40-nm CMOS, the proposed 32.768-kHz TCXO achieves an accuracy of ±4.2 ppm from −20 °C to 85 °C with just three-point trimming and an Allan deviation floor of 34 ppb while consuming 43 nW, which is an approximate 8 \times improvement over the recent state-of-the-art TCXOs.
Published in: IEEE Journal of Solid-State Circuits ( Volume: 57, Issue: 4, April 2022)