A Redundant-Transition-Free and Contention-Free Change-Sensing Flip-Flop

This brief presents a redundant-transition-free low-power flip-flop (FF), named contention-free change-sensing FF (C2SFF). The instability of a previous change-sensing circuit has been discovered under a test scenario where the data input change is uncorrelated with the clock signal. By resolving this instability, C2SFF is always contention-free and has low leakage, while maintaining low dynamic power by eliminating unnecessary transitions of internal clocked nodes. Without additional sizing efforts, C2SFF operates reliably down to 0.32V by removing all contention paths. Post-layout simulation results using a 65 nm CMOS process design kit show that the power consumption of C2SFF is reduced by 62.1%/52.8% with 10%/20% activity at 1V, and 56.9%/49.0% with 10%/20% activity at 0.4V, respectively, compared to transmission-gate FF (TGFF). In addition, C2SFF shows the second-best setup-hold window among tested FFs.