Discussing impedance distribution with multiple stimulating sources in power distribution system design and simulation

Power delivery system (PDS) design becomes more difficult with the requirements of increasing switching speed and decreasing power consumption. Methods have been published and implemented to use pre-defined target impedance as a representation of PDS requirements for selection of decoupling capacitors and configuration of power ground planes. This paper raises and analyzes issues of the target impedance concept in designing PDS, shows that the commonly used definition of target impedance is not a valid measure in many design cases, and proposes other means to truly represent and meet PDS requirement.