On Timing Model Extraction and Hierarchical Statistical Timing Analysis

In this paper, we investigate the challenges of applying statistical static timing analysis in hierarchical design flow, where modules supplied by IP vendors are used to hide design details for IP protection and to reduce the complexity of design and verification. For the three basic circuit types, combinational, flip-flop-based, and latch-controlled, we propose methods for extracting timing models that contain interfacing and compressed internal constraints. Using these compact timing models, the runtime of full-chip timing analysis can be reduced, while circuit details from IP vendors are not exposed. We also propose a method for reconstructing correlation between modules during full-chip timing analysis. This correlation cannot be incorporated into timing models because it depends on the layout of the corresponding modules in the chip. In addition, we investigate how to apply the extracted timing models with the reconstructed correlation to evaluate the performance of the complete design. Experiments demonstrate that using the extracted timing models and reconstructed correlation full-chip timing analysis can be several times faster than applying the flattened circuit directly, while the accuracy of statistical timing analysis is still well maintained.