Thermal-Diffusivity-Based Frequency References in Standard CMOS

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Abstract

In recent years, a lot of research has been devoted to the realization of accurate integrated frequency references. A thermal-diffusivity-based (TD) frequency reference provides an alternative method of on-chip frequency generation in standard CMOS technology. A frequency-locked loop locks the output frequency of an oscillator to the accurate phase shift of an electrothermal filter (ETF). This phase shift is a function of the well-defined thermal-diffusivity of silicon, the rate at which heat diffuses through this material, and the ETF's geometry. This thesis investigates the feasibility of TD frequency references. The first 1.6MHz realization in a 0.7?m standard CMOS is accurate to ±0.1% from -55°C to 125°C. By scaling the ETF and using a 0.16?m CMOS, a second reference generates 16MHz at the same level of accuracy. The scaled reference improves on power consumption, area, and jitter performance of the first implementation, demonstrating that TD frequency references strongly benefit from CMOS scaling.