Power supply impedance emulation to eliminate overkills and underkills due to the impedance difference between ATE and customer board

Abstract

This paper proposes a new type of power supply circuit for automatic test equipment (ATE) that has ability to emulate arbitrary power supply impedance. It can emulate power supply impedance of customer environment so as to match the power supply voltage fluctuation waveforms of the ATE and of the customer environment, in order to eliminate overkills/underkills coming from the voltage fluctuation difference caused by the impedance difference between the ATE and a practical operating environment. Our technique adjusts the equivalent impedance by injecting compensation current by a current source attached in parallel with the power supply source. The compensation current is calculated and injected in realtime with a feedback manner based on the power supply voltage measurement with the impedance characteristics of ATE's original power delivery network (PDN) and the customer PDN. Experimental results of prototype circuits are demonstrated to show that the compensation current emulates the impedance, and the both power supply voltage fluctuation waveforms agree well. Limitations and applications of our method are also discussed.