Reconsidering High-Speed Design Criteria for Transmission-Gate-Based Master–Slave Flip-Flops

In this paper we show that, when dealing with transmission-gate-based master-slave (TGMS) flip-flops (FFs), a reconsideration of the classical approach for the delay minimization is worthwhile to improve the performance in high-speed designs. In particular, by splitting such FFs into two sections that are separately optimized and then reconciling the results, the emerging design always outperforms the one resulting from the employment of a classical Logical Effort procedure assuming such FFs as a whole continuous path. Simulations are performed on several well-known TGMS FFs, designed in a 65-nm technology, to validate the correctness of such a procedure and of the underlying assumptions. Significant improvements are found on delay and, remarkably, on energy and area occupation, thus showing that this approach allows to correctly deal with the actual path effort in such circuits and hence to more properly steer the design towards the achievement of energy efficiency in the high-speed region.