IDDQ Testing

IDDQ testing in practice measures quiescent supply current at multiple distinct test vectors, not just one, since a single static measurement point might happen to avoid activating whatever path a given defect would otherwise expose. A refinement called delta-IDDQ compares the quiescent current measured at consecutive vectors against each other rather than against a fixed absolute threshold, which helps separate a genuine defect signature from ordinary die-to-die and vector-to-vector leakage variation — a distinction that has become increasingly important as background leakage current on advanced nodes has grown large enough to threaten IDDQ's basic defect-detection sensitivity.