Testing defects in scan chains

Applying scan-based DFT, I/sub DDQ/ testing, or both to sequential circuits does not ensure bridging-fault detection, which depends on the resistance of the fault and circuit level parameters. With a "transparent" scan chain, however, the tester can use both methods to detect manufacturing process defects effectively-including difficult-to-detect shorts in the scan chain. The author presents a strategy for making the scan chain transparent. The test complexity of such a chain is very small, regardless of the number of flip-flops it contains.