Exact computation of maximally dominating faults and its application to n-detection tests for full-scan circuits

Abstract

The size of an n-detection test set increases approximately linearly with n. This increase in size may be too fast when an upper bound on test set size must be satisfied. A test generation method is proposed for obtaining a more gradual increase in the sizes of n-detection test sets, while still ensuring that every additional test would be useful in improving the test set quality. The method is based on the use of fault-dominance relations to identify a small subset of faults (called maximally dominating faults) whose numbers of detections are likely to have a high impact on the defect coverage of the test set. Structural analysis obtains a superset of the maximally dominating fault set. A method is proposed for determining exact sets of maximally dominating faults. New types of n-detection test sets are based on the approximate and exact sets of maximally dominating faults. The test sets are called (n,n2)-detection test sets and (n,n2,n3)-detection test sets. Experimental results demonstrate the usefulness of these test sets in producing high-quality n-detection test sets for the combinational logic of ISCAS-89 benchmark circuits.