A 28-nm 368-fJ/Cycle, 0.43%/V Supply-Sensitivity, FLL-Based RC Oscillator Featuring Positive-TC-Only Resistors and ΔΣM-Based Trimming

This brief presents a process-scaling-friendly frequency-locked-loop (FLL)-based RC oscillator. It features an R-R-C frequency-to-voltage converter that entails resistors with only the same-sign temperature coefficients. Together with a low-leakage switched-capacitor resistor and a delta-sigma- modulator-based trimming, our 71.8-MHz RC oscillator in 28-nm CMOS achieves a frequency inaccuracy of 77.6 ppm/°C, a 0.43%/V supply sensitivity, and an 11-psrms period jitter. The energy efficiency is 368 fJ/cycle.