HyAC: A Hybrid Structural SAT Based ATPG for Crosstalk

As technology evolves into the deep sub-micron era, signal integrity problems are growing into a major challenge. An important source of signal integrity problems is the crosstalk noise generated by coupling capacitances between wires. Test vectors that activate and propagate crosstalk noise effects are becoming an essential part of design verification and manufacturing test. However, deriving such vectors is a complex task. In this paper, we propose HyAC, a fast yet accurate hybrid ATPG method targeting multiple-aggressor induced crosstalk errors. Given a victim and a set of aggressors, the proposed ATPG method searches for test vectors to activate and propagate a crosstalk error for the victim. Due to logic constraints, it may not be possible to trigger all aggressors simultaneously. Therefore, firstly we use an implication graph (IG) that consists of logic variables and structural information to check for logic conflicts. If the current set of aggressors is not feasible, our algorithm automatically searches for the next-best subset of aggressors (resulting in the largest noise). After a set of feasible aggressors is identified, we use a modified PODEM [21] algorithm to search for test vectors. This hybrid structural SAT-based ATPG method inherits advantages from both Boolean– satisfiabilitity based methods and structural-based methods to achieve flexibility and efficiency. We demonstrate the accuracy, high quality, and run time efficiency of HyAC through experiments conducted on several benchmark circuits as well as a circuit from a commercial processor.