Small Delay Fault Simulation for Sequential Circuits

Small-delay faults may escape detection by transition fault patterns, but traditional transition fault simulator can not detect this phenomenon. A fault simulator detecting test escape of small-delay faults is presented. The sizes of the faults are less than one system clock cycle. For our method, the delay distribution in the CUT is considered, and the fault size is quantized as times of the propagation delay in an inverter. By a waveform simulation based on Boolean process, the simulator is able to show the time interval that the fault affects and determine whether the propagation delay exceeds the system clock cycle. It might give ATPG a little of useful information.