Comparing Voltage Adaptation Performance between Replica and In-Situ Timing Monitors

Adaptive voltage scaling (AVS) is a promising approach to overcome manufacturing variability, dynamic environmental fluctuation, and aging. This paper focuses on timing sensors necessary for AVS implementation and compares in-situ timing error predictive FF (TEP-FF) and critical path replica in terms of how much voltage margin can be reduced. For estimating the theoretical bound of ideal AVS, this work proposes linear programming based minimum supply voltage analysis and discusses the voltage adaptation performance quantitatively by investigating the gap between the lower bound and actual supply voltages. Experimental results show that TEP-FF based AVS and replica based AVS achieve up to 13.3% and 8.9% supply voltage reduction, respectively while satisfying the target MTTF. AVS with TEP-FF tracks the theoretical bound with 2.5 to 5.6% voltage margin while AVS with replica needs 7.2 to 9.9% margin.