Slide 79 of 173
Notes:
As noted before, IDDQ measurement is the biggest stumbling block. What’s typically done is to apply the test and power from the tester’s power supply and then remove it. A defectless device will maintain its output levels for a fairly long time because of the low IDDQ. A device with an IDDQ-detectable fault will discharge faster. This RC time constant measuring method is the main reason IDDQ testing takes so long.
Several techniques for on-chip IDDQ measurement have been theorized, but not implemented. This technique would be necessary for IDDQ BIST.
