A Novel One-Step Calibration Method for On-Chip Oscillator

Abstract

A novel one-step calibration method with no iteration and high trimming accuracy for on-chip oscillator is proposed. The concept is to count oscillator cycles within a specified reference period of time, and take the count value as the trimming code of oscillator to achieve the targeted frequency. To demonstrate the effectiveness of this method, an on-chip RC relaxation oscillator with 8-bits trimming signal has been designed, analyzed and verified with a 0.5um CMOS technology. Simulation results show that the oscillator achieves a low frequency variation of $\pm 0.8\%$ over $+45\%$ process variation of resistor and capacitor after one-step calibration.