Practical use of transition mode delay to solve the problems of floating mode delay under highly correlated input streams

The possible overestimation of timing analysis under the floating mode has been known for more than five years. However the transition mode that can resolve the problem has not been widely employed in real designs due to the following reasons: (1) the source of the overestimation of the floating delay has not been thoroughly analyzed, (2) the previous transition delay computing method based on the symbolic simulation is not as efficient as that for the floating delay, and (3) the importance of the transition delay has not been sufficiently demonstrated by experiments. In this paper, we first present a thorough and formal analysis on the reasons of the overestimation of the floating delay including ones caused by the spatio-temporal correlation among the primary input signals. Based on the analysis, we present a new practical sensitization criterion for the transition mode. Experimental results validating our work are also included