Diagnostic Test Sets with Increased Switching Activity for Transition Faults

Test sets with excessively high switching activity can cause voltage drops that may result in overtesting. If overtesting is avoided, tests with increased switching activity are preferred since the tests detect more delay faults, and they exercise the circuit better. For delay fault diagnosis, this paper observes that tests with increased switching activity also have the advantage that they can cause responses of modeled faults to match the observed responses of faulty chips better. Motivated by this observation, the paper describes a procedure that produces diagnostic test sets with increased switching activity targeting transition faults. The procedure accepts a fault detection test set. In the first part, the procedure modifies the tests in order to increase their switching activity. In the second and third parts, the procedure adds diagnostic tests with increased switching activity. Experimental results demonstrate the extent to which it is possible to increase the switching activity of a diagnostic test set.