Testing of mixed signal (analogue and digital) circuits (ASIC and board level) using current monitoring techniques

Supply current monitoring as an approach to the test of purely digital CMOS circuits has already attracted considerable interest; it remains to investigate its applicability to analogue and mixed signal circuits. In this approach the current passing through the VDD or GND terminals is monitored during the application of test vectors. In the quiescent state such circuits draw a very low (nano-amp) current. This is raised by several orders of magnitude in the presence of certain defects thus offering a means of detecting these defects. The technique offers the advantages of direct detection of the defect obviating any necessity to propagate a defective voltage to an output port. It is also able to detect certain defects missed by traditional voltage test approaches based on the 'stuck-at' fault model.<>