PCB Effects on On-chip Capacitor Requirements and an Efficient Resonance-Prevention ASIC Methodology Open Access

A method for determining adequate quantities and locations of on-chip capacitors to maintain supply voltages at all locations on a chip within pre-specified limits given the switching activity of on-chip circuits was presented in [3]. In this paper, we extend the method to include current flow from the package and PCB. The effects of on-chip capacitance and other system parasitics on the time it takes for additional supply current to flow into a chip are discussed. The relationship between switching current, capacitance, system parasitic inductances, and on-chip noise is presented. These concepts are then applied to the subject of power delivery network (PDN) resonance. A 1-dimensional model for simulating PDN resonance is presented. The model includes chip, package, and PCB components, along with explicit networks for each chip power supply and their interactions. The topology of the model and the contributions of each model component are described. A design methodology for avoiding PDN resonance, presently in use on all IBM ASIC modules, is presented.