Investigation of Voltage Regulator Module (VRM)-Induced Noise to High-Speed Signals With VRM via Design Factors

Abstract

As the complexity of server platforms increases, the noise produced by switching voltage regulator modules (VRMs) is more likely to be coupled to nearby high-speed traces. This study aims to investigate the mechanism of noise coupling between the noise generated by a VRM and a high-speed signal trace, as well as to evaluate various noise-reduction methods. A VRM's rapid switching of field effect transistors generates an unintentional coupling region that primarily injects noise into high-speed traces routed in the inner signal layers of the printed circuit boards (PCBs) in server platforms. To analyze various VRM noise coupling mechanisms in practical high-speed channels, a simplified PCB design based on a high-speed server platform is designed and fabricated. In addition, case studies are conducted under various conditions to validate the most efficient VRM noise coupling reduction method by both simulation and measurement. Finally, various design factors that influence VRM noise coupling are evaluated to propose guidelines for high-speed channel designers. This study presents the first comprehensive analysis of different noise coupling mechanisms and an IR drop aware guideline to reduce noise in dense high-speed systems containing a VRM.