Simplified evaluation of power bus resonances on fully populated high speed digital PCBs

The ever increasing clock rate and bandwidth of the digital signals, running on today´s printed circuit boards, have forced more attention to be paid to study the resonances of the planes distributing the power to the active devices on the board. Simple simulation models have to be developed, so that no deep theoretical knowledge and costly simulation tools are asked of the designers for the analysis of the power bus resonances. The paper discusses simple and effective models applied to the power bus structure of a fully populated multilayer board, where an integrated circuit with a very large package provides a lot of digital signals with rise/fall times of about 400ps. The measurements carried out on the transfer impedance of the power bus are finally presented and the good matching with the simulation confirm the validity of the model.