A low-jitter phase-locked resonant clock generation and distribution scheme

Clock distribution networks have traditionally been optimized to minimize end-to-end delay of the distribution network. However, since most digital ICs have an on-chip PLL, a more relevant design goal is to minimize cycle-to-cycle jitter. In this paper, we present a novel low-jitter phase-locked clock generation and distribution methodology which uses resonant standing wave oscillators (SWOs). In contrast to traveling wave oscillator rings (TWOs or “rotary” clocks), our SWO achieves the same phase at every point in the ring, making it amenable to a synchronous design methodology. The standing wave oscillator is controlled by coarse as well as fine tuning. Coarse tuning is achieved by varying the ring inductance, while fine tuning is accomplished by varying the ring capacitance. Clock distribution is done by routing the resonant ring chip-wide in a “comb” like manner. Experimental results demonstrate that the cycle-to-cycle jitter and skew of our approach is dramatically lower than existing schemes, while the power consumption is significantly lower as well. These benefits occur due to the resonant nature of our SWO-based clock generation and distribution approach.