Design-for-testability techniques for detecting delay faults in CMOS/BiCMOS logic families

The delay fault testing in logic circuits is studied. It is shown that by detecting delayed time response in a transistor circuit, two types of faults are detected: (1) faults which cause delayed transitions at the output node due to some open defects and (2) faults which cause an intermediate voltage level at the output node. A test circuit is presented which enables the concurrent detection of delay faults. The proposed delay fault testing circuit does not substantially degrade the speed of the circuit under test (CUT). Simulation results show that this technique fits any design style.