Detecting FET Stuck-Open Faults in CMOS Latches And Flip-Flops

The authors present evidence that conventional tests cannot detect FET stuck-open faults in several CMOS latches and flip-flops. Examples are given to show that stuck-open faults can change static latches and flip-flops into dynamic devices¿a danger to circuits whose operation requires static memory, since undetected FET stuck-open faults can cause malfunctions. Designs are given for several memory devices in which all single FET stuck-open faults are detectable. These memory devices include common latches, master-slave flip-flops, and scan-path flip-flops that can be used in applications requiring static memory elements whose operation can be reliably ascertained through conventional fault testing methods.