The analysis of digital integrators for test response compaction

The compaction properties of integrators that could be used in the built-in self-test (BIST) environment instead of linear finite-state-machine-based comparators are studied. Markov chain models are used to provide a quantitative characterization of the compaction scheme in terms of its steady-state behavior as well as its transient properties. It is demonstrated that the asymptotic fault coverage drop depends on the fault injection site, the fault injection probability, and the gain factor. A simple modification of the standard integrator is also proposed in order to improve the quality of compaction. The proposed scheme introduces very small hardware overhead. It is compatible with the width of the data path, and the test can be applied at the normal mode speed