Estimation of Microprocessor Instantaneous Load Current

The inability to accurately determine the die level current draw of microprocessors is a significant gap in the analysis and design of microprocessor power delivery networks (PDNs). Although low frequency methods of direct measurement are available, the large number of power and ground connections on a package makes high frequency measurements extremely difficult. This paper successfully demonstrates that the instantaneous load current can be accurately estimated to over 500 MHz with only a wide bandwidth measurement of the voltage at the die. The current estimate is obtained by using the measured output impedance to create a band-limited inverse filter to solve the linear deconvolution problem. The accuracy of the algorithm is verified by correctly estimating known loads drawn by a functioning microprocessor. Two separate methods are then used to estimate the instantaneous load current of a microprocessor executing instructions, and wide bandwidth ${\rm i}_{\rm o} ({\rm t})$ results are presented and discussed.