Signature analysis for fault detection of mixed-signal ICs based on dynamic power-supply current

In this paper we have investigated a unified and simultaneous fault detection method for mixed-signal integrated circuits. The method is based on the analysis of the power-supply current through the circuit under test. The analysis has been done paying attention to the dynamic behaviour of the power-supply current, in order to avoid measurement problems related to the large amount of quiescent current drop across many analog blocks. The analysis of the dynamic power-supply current entails certain problems related to the complexity of the measurement process, especially those due to the high speed of the current transients. These problems have been addressed by considering a design for test procedure based on the use of built-in dynamic current sensors. The goal of the design for test methodology proposed is to represent the Iddt through the mixed-signal IC under test by a digital signature~ The paper presents some advantages of this approach such as a good tolerance to crosstalk noise and the need for only a conventional digital tester on the complete mixed-signal IC for fault detection. The analysis is illustrated with some test results.