A DFT technique to increase the resolution of AC RMS power supply current monitoring of complex analogue circuits

RMS AC supply current monitoring with the addition of the novel DFT technique presented in this paper shows an increase in fault coverage for an embedded opamp from only 2.5% to over 70%. During a test, the effective width-length ratio of the transistors that draw the most AC current is reduced, causing the supply current drawn by other parts of the circuit that might be faulty to contribute relatively more to the overall supply current, allowing detection of faults. The results of Monte Carlo fault simulations demonstrate the principle. The most significant advantages of this DFT technique are increased fault coverage; small (1%) area overhead; and low impact on the performance of the circuit