An R-RC Oscillator Achieving Second-Order Temperature Compensation and Oscillating Independently From the Comparator and Reset Delays

This article presents a second-order temperature-compensated R-RC oscillator with a detailed analysis and design methodology. The proposed R-RC oscillator leverages a novel R-RC configuration that cancels both first- and second-order temperature dependencies at the same time, achieving a low-temperature coefficient in a wide temperature range. The R-RC oscillator proposes a delay-locked loop (DLL) to exclude undesirable delays of the comparator and reset switch, enabling the final reference frequency to be determined by only the time constant of the R-RC configuration. For verification, the oscillator was fabricated in a 0.18- $\mu $ m standard CMOS technology. It generates a frequency reference of 2.3 MHz while occupying an active area of 0.07 mm² and consuming $7.6~\mu $ W at room temperature. A total of 11 chips are measured and the proposed R-RC oscillator achieves an average temperature coefficient (TC) of 7.93 ppm/°C across a temperature range from $- 40~^{\circ }$ C to $125~^{\circ }$ C and an energy efficiency of 3.3 pJ/Hz.