On The Bound Of Time-Domain Power Supply Noise Based On Frequency-Domain Target Impedance

One of the popular design methodologies for power distribution networks (PDNs) is to identify a target impedance to be met across a broad frequency range. The methodology is based on the assumption that the ratio of the time-domain maximum output voltage noise to the multiplication of target impedance and time-domain maximum input current is no more than one. In this paper, the ratios for different impedance profiles are analyzed, and the assumption is proved to be not necessarily true. Particularly, for second-order impedances, the maximum ratio can be two. Several cases with real PDN structures are investigated to support our analysis. A real case of the complete PDN path with the ratio of 1.585 is given.