A fast untestability proof for SAT-based ATPG

Automatic Test Pattern Generation (ATPG) based on Boolean satisfiability (SAT) has been shown to be a beneficial complement to traditional ATPG techniques. SAT solvers work on instances given in Conjunctive Normal Form (CNF). The required transformation of the ATPG problem into CNF is one main part of SAT-based ATPG and needs a significant portion of the overall run time. Solving the SAT instance is the other main part. Here, the time needed is often negligible - especially for easy-to-classify untestable faults. This paper presents a preprocessing technique that speeds up the classification of untestable faults by accelerating the SAT instance generation. This increases the robustness of the entire ATPG process. The efficiency of the proposed method is shown by experiments on large industrial designs.