Jitter and Phase Noise in Ring Oscillators

Summary

Closed-form expressions for the rms and dc values of the ISF were obtained for single-ended and differential oscillators with equal and unequal rise and fall times. These approximate expressions were used to obtain approximate analytical expressions for phase noise and timing jitter in ring oscillators in terms of design parameters such as power dissipation, frequency of oscillation and number of stages. The effect of correlated noise sources on jitter and phase noise was analyzed. Design questions such as the optimum number of stages, and choice of differential vs. single-ended topology were answered. Experimental results were compared to the theoretical predictions and good agreement was observed.