Filtering Techniques and Topologies with Positively and Negatively Coupled Inductors for Dense Low Cost Packages and Platforms

Merger of multiple loads on single voltage rail results in increase in self and coupling noise due to close proximity of load spatial distribution and limited package resources for individual isolation inductor. This paper presents a new filtering technique to mitigate self and cross-noise concerns on multiple closely spaced cascaded loads via positive and/or negative coupled inductors and carefully designed coupling polarities. Analytical descriptions and detailed evaluations for two and three load systems are discussed. Transient and frequency domain simulation results validate the theory showing up to 67% noise mitigation. In addition, approximately 3X area reduction is shown to be feasible. Design guidelines are derived to decide choice of mutual inductance and coupling polarities to maximize design benefits.