Evaluating Fault Coverage of Structural and Specification-based Tests Obtained With a Low-Cost Analog TPG Tool

This work presents an evaluation of a previously proposed low-cost automatic test generation tool for analog circuits. In this investigation, the fault coverage (FC) estimated by the tool, which is based on structural fault modeling with low-cost test measurements, is compared with the FC obtained by evaluating a set of functional parameters of the circuit under test. The entries of this tool are the spice netlist, the technology models of the circuit and a defect model defined by the user. With this information, the tool interacts with a spice simulator, simulating the fault-free and faulty circuits. The test development considers DC, AC (single tone) and transient (step) stimuli applied at the primary circuit inputs, computing the obtained fault coverage when taking different circuit nodes as observation points. Furthermore, a specification-based test set, with three functional parameters, was considered in order to compare the results. The considered case study is a fully-differential integrated filter designed on a commercial 180 nm process. Results show a fault coverage of 96.25%, obtained by four structural tests requiring small test sequences with simple parametric measurements. On the other hand, the fault coverage considering the specification-based test, results in a test set with four tests with a fault coverage of 84.68%.