Diagnosis of delay faults due to resistive bridges, delay variations and defects

In this paper, we present the first diagnosis algorithm for combinational circuit blocks that considers all combinations of multiple gate/wire delay variations/defects and any single resistive bridge. One key component of the proposed algorithm is a new path-oriented effect-cause procedure to identify all possible suspects of above type that might have caused the timing errors observed during test. The second key component is an efficient data structure to represent the suspects. The third key component is a new algorithm to analyze passing tests to vindicate some of the suspects identified. This algorithm exploits the newly identified concept of fixed-but-unknown delays, i.e., the fact that during the period of diagnosis the values of all delay parameters for every gate and wire in the particular circuit under test remain fixed, although at values unknown to us. The final set of suspects reported by the algorithm is guaranteed to contain all possible causes of the observed timing errors. Experimental results on benchmark circuits show the effectiveness of the proposed approach