Fundamentals of Power Integrity for Computer Platforms and Systems

Chapter 4Power Distribution Network

The power distribution network PDN analysis has traditionally been the primary technical focus for power integrity engineers. It involves examining the impedance of the distribution path between the source and the load in the frequency domain. The reason for examining this network—rather than simply looking at the voltage droop at the package—is that critical signal behavior is unveiled through understanding the PDN, and often the analysis can be completed with minimal information from the silicon teams. The efficacy of the power signal from the load to the source is also an important factor in the integrity of the system power behavior. Additionally, from the amplitude and frequency of the key peak resonances in the impedance profile, insights could be gained as to where potential droop events could occur. Thus, usually the study consisted of examining the distribution path but occasionally including the load and sources in the system. (The load and the source for the system will be examined in later chapters.)

The distribution path contains power planes, parasitics, and sometimes a socket, a package, and the decoupling between the load and source. The source usually refers to the voltage regulator behavior and load behavior of the silicon. It is common practice to SPICE or the math-based program in analyzing this system to get a sense of its overall behavior. Actually, many good tools are available that can do this job, and the reader is ...