The LT4180 forces the output current to change from 95% and 105% of the nominal output current at a pre-determined dither frequency. In other words, the LT4180 forces a square wave current with a peak-to-peak amplitude of ±5% on top of the regulators output current. A decoupling capacitor filters out the dither current from the VRS square wave at the load. The decoupling capacitor is sized to produce an “AC short” at the square wave frequency, resulting in a voltage square waveform produced at the power supply with a peak-to-peak amplitude equal to 1/10 of the line impedance. This direct measurement of the voltage drop across the wiring is monitored and the LT4180 corrects the feedback loop of the regulator to provide accurate load regulation. The error voltage (∆V) can be represented by Ohm’s law (V=IR), or ∆V = ∆IL X Line Impedance. Since ∆IL is ±5% and the ∆V is measured, the line impedance can be determined.