Comparative analysis of power yield improvement under process variation of sub-threshold flip-flops

In low power synchronous systems, sub-threshold flip-flops are used to reduce the total power dissipation. Moreover, process variations create a large variability in the flip-flop power in scaled technologies impacting the power yield, especially, for sub-threshold operation. This paper presents an analysis of power yield improvement of four commonly used flip-flops under process variations. These flip-flops are designed using STMicroelectronics 65-nm CMOS technology. The analyzed flip-flops are compared for delay, energy, and energy-delay product (EDP) overheads to achieve this power yield improvement. The analysis shows that the sense amplifier based flip flop (SA-FF) has the lowest overheads while the modified clocked CMOS master slave flip-flop (M-C²MOS-MSFF) exhibits the largest overheads, and correspondingly, it is not recommended for sub-threshold operation.