N-Detection Test Sets for Circuits with Multiple Independent Scan Chains

Abstract

In a circuit with multiple independent scan chains, it is possible to operate groups of scan chains independently in functional or shift mode. This design-for-testability approach can be used to increase the quality of a test set. This article describes an N-detection test generation procedure for increasing the quality of a transition fault test set in such a circuit. The procedure uses the possibility of applying the same test, with the scan chains operating in different modes, to increase the numbers of detections without increasing the number of tests that need to be generated or stored on a tester. This results in reduced input storage requirements compared with a conventional N-detection test set and an increased number of applied tests. The increased quality of the test set is verified by its bridging fault coverage.