Boundary-Functional Broadside and Skewed-Load Tests

Abstract

Close-to-functional broadside tests are used for avoiding overtesting of delay faults that can result from non-functional operation conditions, while avoiding test escapes because of faults that cannot be detected under functional operation conditions. When a close-to-functional broadside test deviates from functional operation conditions, the deviation can affect the entire circuit. This article defines the concept of a boundary-functional broadside test where non-functional operation conditions are prevented from crossing a preselected boundary. Using the procedure described in this article, the boundary maintains the same values under a boundary-functional broadside test as under a functional broadside test from which it is derived. Indirectly, this ensures that the deviations from functional operation conditions throughout the entire circuit are limited. The concept of a boundary-functional broadside test is extended to skewed-load tests, and to partial-boundary-functional tests. Experimental results are presented for benchmark circuits to demonstrate the fault coverage improvements that can be achieved using boundary-functional broadside and skewed-load tests as well as partial-boundary-functional tests of both types.