Abstract: A high-frequency supply voltage waveform is sampled from a functioning integrated circuit. This waveform is measured at (or coupled closely to) a power supply node on the integrated circuit. A low-frequency supply current waveform is sampled concurrently with the sampling the high-frequency supply voltage waveform. This waveform is measured at a power supply node external to the integrated circuit. A power supply network providing power to the integrated circuit is modeled with a circuit model. The power supply network is modeled using the high-frequency supply voltage waveform as an input to the circuit model. A simulation output is taken at a simulated power supply node corresponding to the power supply node external to said integrated circuit. Based on a comparison of the simulated low-frequency supply current waveform and the low-frequency supply current waveform, a value of at least one component of the circuit model is adjusted.