Spot Defect Diagnosis in Analog Nonlinear Circuits with Possible Multiple Operating Points

The paper is focused on local spot defect diagnosis in nonlinear analog integrated circuits. The defects are simulated by finite resistors, high in the case of open and low in the case of short. A diagnostic method that allows detecting, locating, and estimating the value of the defect is developed. The method employs the simulation before test approach leading to a fault dictionary and brings a procedure for locating the defect and estimating its value, on the basis of some quantities measured during the diagnostic test. Because the nonlinear circuit under test may have multiple operating points, even if the fault-free circuit has a unique solution, building the fault dictionary requires a special approach. It is based on some families of characteristics, expressing the resistances that simulate the defects in terms of several voltages, taking into account the deviations of the fault-free parameters within their tolerance ranges. To illustrate the proposed approach two numerical examples are given.