A 1-mu W/MHz RC Oscillator With Three-Point Trimmed 2.1-ppm/degrees C and Single-Point Trimmed 8.7-ppm/degrees C Stability From-40 degrees C to 95 degrees C

This article presents techniques to improve the frequency stability of RC oscillators by performing first- and second-order temperature compensation without needing resistors with opposite temperature coefficients (TCs). Using the proposed three-point digital trim, a prototype 100-MHz frequency-locked loop (FLL)-based RC oscillator fabricated in a 65-nm CMOS process achieves an inaccuracy of +/- 140 ppm over -40 degrees C to 95 degrees C, 83-ppm/V voltage sensitivity, 1.3-ppm Allan deviation floor, and 1-mu W/MHz power efficiency. When only a single-point trim is performed using a multiple linear regression model leveraging the strong correlation between three switched resistors, the frequency inaccuracy is +/- 587 ppm.