Optimization of analog fault coverage by exploiting defect-specific masking

Abstract

A new method is presented to detect catastrophic defects from the signal analysis of dynamic current consumption waveforms of analog circuits. While other techniques use the whole information in a Root-Mean-Square computation or in black-box techniques such as a neural network, the central point of this work resides in the selection of waveform samples to create a signature able to discriminate a defective circuit from a fault-free circuit. The selection of samples is implemented by the introduction of binary vectors to partially mask the data. Confronted with process variations, this technique offers the advantage of being straightforward and simple to implement in Automated Test Equipments. The generation of the masks is optimized to improve the defect coverage by means of a genetic algorithm maximizing the distance between the signature of the fault-free circuit and a faulty circuit. Results from simulations on industrial circuits show that the number of detected defects can be nearly doubled for specific stimuli.

Design and test of analog circuits towards sub-ppm level

“…According to the 6-fault model used, the circuit has 94 possible faults, out of which less than 50% are detectable with typical specification testing. Using targeted test stimuli and applying defect-specific masking on the measured waveforms, the fault coverage can increase significantly [1,4]. For example, figure 3 clearly shows the increase in fault coverage when applying a sinewave excitation (S1, S2 or S3) on the supply voltage and using no/simple/optimized masking on the measured time-domain power-supply current waveform [4].…”

“…Using targeted test stimuli and applying defect-specific masking on the measured waveforms, the fault coverage can increase significantly [1,4]. For example, figure 3 clearly shows the increase in fault coverage when applying a sinewave excitation (S1, S2 or S3) on the supply voltage and using no/simple/optimized masking on the measured time-domain power-supply current waveform [4]. Similar results have been obtained for other stimuli and measured signals, increasing the fault coverage far above the typical specification testing for this circuit.…”

Automated testing of mixed-signal integrated circuits by topology modification

“…These signatures can be as simple as the measurement of the current consumption or of a node voltage. It is also possible to use signatures such as a Fast-Fourier-Transform or more sophisticated scheme based on measured transient signals [15].…”

Low-Cost Defect Simulation Framework for Analog and Mixed Signal (AMS) Circuits with Enhanced Time-Efficiency

“…On the other hand, the defect testing methods for analog and mixed signal circuits are still challenging due to their design complexity. Also, the fact that, in an SoC, the major portion of field returns are due to fails in analog circuits [6] stresses the need for increased defect coverage testing for analog circuits. Hence, due to all the stated reasons, the area of defect-oriented testing for AMS circuits is one of the hot topics [2], [4].…”