Cross-SSN analysis in multilayer printed circuit boards

Abstract

As digital circuits became faster and more power is involved, direct coupling in multilayer printed circuit boards (PCBs) among power (PWR) planes becomes a major concern for signal integrity (SI) and electromagnetic interference (EMI). Aim of this paper is to show how an electromagnetic wave can propagate between planes and therefore induce noise on the signals crossing the planes' pairs through vias eventually radiate from the edge of the board. More specifically our study focuses on the analysis of the noise which propagates from a power plane to another power plane due to their proximity, named cross-simultaneous switching noise (X-SSN). This effect can be mitigated by a careful analysis of the location of PWR and ground (GND) planes in the board stack-up which avoid the contiguity of two PWR planes. A test board is built and measurements are performed. These measurements are also compared with three dimensional numerical results.