DIAGNOSABILITY ANALYSIS OF ANALOG CIRCUITS

If a circuit has been found to be faulty during design characterizatio n before it is in high volume production, it may be useful to diagnose the cause of the failure. If faults are identified and located, a cir cuit can then be redesigned to be less sensitive to common failure mec hanisms. Fault diagnosability analysis is an approach to enhancing the diagnosabilty of a circuit. Whereas the design for diagnosability ens ures that the test points are properly selected and the generation of tests is considerably simplified, diagnosability analysis is used to l ocate sections of a circuit having poor diagnosability. The informatio n allows estimation of a circuit's diagnosability before the fault dia gnosis is attempted. Hence any potential problem can be located early on the design phase, allowing modifications to be introduced to improv e the final diagnosability of the circuit. This paper presents a simpl e diagnosability analysis process in which the diagnosability of a cir cuit is measured from a graph that describes the circuit topology and a given set of test points, and no circuit simulation is needed. Since the graphical description of a circuit topology is not unique, the de veloped diagnosability analysis will find a graph with the maximum dia gnosability that the circuit can possibly achieve, and identify the co mponents/sub-circuits with poor diagnosability. (C) 1998 John Wiley & Sons, Ltd.