Diagnostic Test of Robust Circuits

Robust circuits are able to tolerate certain faults, but also pose additional challenges for test and diagnosis. To improve yield, the test must distinguish between critical faults and such faults, that could be compensated during system operation, in addition, efficient diagnosis procedures are needed to support yield ramp-up in the case of critical faults. Previous work on circuits with time redundancy has shown that "signature rollback" can distinguish critical permanent faults from uncritical transient faults. The test is partitioned into shorter sessions, and a rollback is triggered immediately after a faulty session. If the repeated session shows the correct result, then a transient fault is assumed. The reference values for the sessions are represented in a very compact format. Storing only a few bits characterizing the MISR state over time can provide the same quality as storing the complete signature. In this work the signature rollback scheme is extended to an integrated test and diagnosis procedure. It is shown that a single test run with highly compacted reference data is sufficient to reach a comparable diagnostic resolution to that of a diagnostic session without any data compaction.