Criticality-dependency-aware timing characterization and analysis

For nanometer design, conventional timing analysis may generate over-optimistic results on criticality-dependent paths. A late arrival time at the data input of a flip-flop lengthens the propagation delay from the clock pin to the data output of this flip-flop, thus degrading the timing margins of paths launching from this flip-flop. To remove the optimism, in this paper, we first propose a simple yet effective triangle model to characterize the criticality-dependency effect. Then, we devise a novel criticality-dependency-aware timing analysis flow, which is seamlessly integrated with the common static timing analysis flow. Experimental results show that our approach can effectively analyze the criticality-dependency effect: Based on the proposed triangle model, we can accurately identify all timing-risky flip-flops and capture the induced timing margin degradation.