Nonoverlapping Power/Ground Planes for Suppression of Power Plane Noise

Abstract

Providing low IR -drop and inductance are two major roles of power and ground (PG) planes in chip packages and boards. However, planes can also cause switching noise coupling, especially when they resonate. This is a concern for mixed-signal boards, high-speed I/Os, and electromagnetic compatibility. Discrete decoupling capacitors are ineffective to control switching noise at gigahertz frequency regime due to their inductance. To filter such high-frequency noise, a possible approach is modifying the shape of the PG planes, such as in power islands or electromagnetic bandgap structures. In this paper, we introduce the nonoverlapping PG planes design methodology for filtering of gigahertz power plane noise. Unlike existing approaches, our approach is simple and has wide bandwidth, while avoiding narrow inductive bridges that increase IR -drop.