Generation of optimum test stimuli for nonlinear analog circuits using nonlinear programming and time-domain sensitivities

In this paper a novel approach for the generation of an optimum transient test stimulus for general analog circuits is proposed. The test stimulus is optimal with respect to the detection of a given fault set by means of a predefined fault detection criterion. The problem of finding an optimum test stimulus detecting all faults from the fault set is formulated as a nonlinear programming problem. A functional describing the differences between the good and all faulty test responses of the circuit serves as a merit functional for the programming problem. A parameter vector completely describing the test stimulus is used as the optimization vector. The gradient of the merit functional required for the optimization is computed using time-domain sensitivities. Since in this approach the evaluation of the fault detection criterion represented by the merit functional flows directly into the computation of the test stimulus, optimal test stimuli for hard to detect faults can be generated. If more than one input terminal is used for testing, several test stimuli can be generated simultaneously