Robustness to Voltage Noise With Ring Oscillator Clocks

Voltage noise is the main source of dynamic variability in integrated circuits and a major concern for the design of power delivery networks (PDNs). Lower supply voltages were made possible with technology scaling, but power density was also increased. Consequently, power integrity became a key factor in the design of reliable high performance circuits. Ring oscillators clocks (ROCs) have been proposed as an alternative to mitigate the negative effects of voltage noise. However, the effectiveness highly depends on the design parameters of the PDN, power consumption patterns, and spatial locality of the ROC within the clock domain. This paper analyzes the impact of the PDN parameters and ROC location on the voltage noise and the robustness achieved by using ROCs. The capability of reacting instantaneously to large voltage droops makes ROCs an attractive solution, which also allows to relax the constraints required for the PDN design. The experiments show that up to 83% of the margins for voltage noise and up to 27% of the total leakage power can be reduced by using ROCs. In addition, PDN simplifications are possible, with fewer power interconnections or package decoupling capacitors of lower quality. Tolerance to voltage noise and related benefits can be increased with multiple ROCs.