The Quantitative Measurement of the Effectiveness of Decoupling Capacitors in Controlling Switching Transients from Microprocessors

Power distribution systems (PDS) are typically comprised of capacitor networks that have several types of capacitors and values to obtain a targeted impedance over the required frequency spectrum for the PDS planes on a printed circuit board (PCB). Capacitors serve two primary roles in meeting the targeted impedance. The first role is to provide a temporary source of localized energy for instantaneous current demands from an IC; the second is to provide a low-impedance return path for high frequency noise. This paper proposes a time-domain test to evaluate a capacitor’s performance and effectiveness to meet these two primary roles.