Testing multiple stuck-at faults of ROBDD based combinational circuit design

Abstract

As technology scales, small and dense geometries, and process variations introduce defects that are often not detected by single stuck-at tests. To improve defect coverage, we expand the single stuck-at tests to cover multiple stuck-at faults. This paper investigates multiple stuck-at fault (MSAF) testability of ROBDD (Reduced Ordered Binary Decision Diagram) based fully delay testable combinational circuits. The circuits are derived by covering ROBDD nodes with Invert-And-Or sub-circuits(2:1 muxes). We show that for each sub-circuit which acts as a partition, the multiple stuck-at fault test set needs only four vectors. Additionally we prove that multiple stuck-at fault test set for the complete circuit has an upper bound of 3N test vectors where N is node count of the ROBDD representing the circuit.