A Fully Differential Distributed RC Oscillator With a Suppression of Noise and Temperature Sensitivities

This paper presents a fully differential distributed RC oscillator implemented within a frequency-locked loop (FLL). It employs a frequency error detector in the differential distributed RC network to boost the transition slopes while staying within supply rails in the feedback loop, thereby increasing the frequency-to-voltage gain and mitigating overall noise. The design also features a second-order temperature compensation that integrates a coarse 4 b temperature sensor, polynomial calculation, and a Delta-Sigma Modulator (DSM) to regulate the reference voltage over temperature. Fabricated in 0.18 lm CMOS, the 1.26 MHz oscillator achieves an rms period jitter of 89.9 ps (0.011 %), an Allan deviation floor of 0.52 ppm, and temperature sensitivities of 7.14 ppm/0C for second-order, while consuming 252 lW at a supply voltage of 1.8V.