Frequency dependencies of power noise

Abstract

In this paper, frequency dependencies of delta-I noise caused by variations of the on-chip switching activity have been analyzed by simulations for a complex computer system board with multi-chip module, especially the impact of coincidences with resonances of the power distribution system. The switching frequency and the noise source waveform have been varied in case of a single delta-I step. For repeated delta-I steps the power noise dependencies on the repetition frequency, the duty cycle and the damping of the resonant loop have been analyzed. Simulations using switching current sources for on-chip switching have been confirmed by simulations with switching resistors plus de voltage source. Mid-frequency noise simulations using SPEED2000 and noise voltage measurements yield the same results within 6% for the first and second voltage droops and overshoots, if the real resistance of power/ground vias and module pins are included in the simulation.