Measuring VRMs, PDNs (power distribution networks), capacitors, and inductors, requires measurement accuracy in the milliOhms range – whether it’s inductor DCR, VRM output impedance, or capacitor ESR. This requires you to use the 2-port shunt measurement to achieve this accuracy. Yet, often the DUT impedance range is large, spanning many orders of magnitude beyond what the 2-port measurement can handle. This article discusses the limits of this popular measurement setup and how to extend them in order to measure larger impedance ranges than would otherwise be possible with the 2-port measurement alone.
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