SMPS electromagnetic noise in System-on-Chip: Resonant frequency and amplitude dependencies
Résumé
Electromagnetic noise (EMI) is always difficult to estimate especially inside complex System-on-Chips (SoCs) where multiple noise sources and victims share the same silicon. However when a Switch-Mode Power Supply (SMPS) power stage is integrated in a SoC, switching noise becomes an issue of concern. The use of Technology Computer Aided Design solutions (TCAD) such as Finite Element Method (FEM) solver to model the emission and propagation of this noise has become highly time consuming in large SoCs. Consequently it is necessary to understand noise mechanism to reduce model complexity and to set up adapted solutions. The source analysis is based on a Spice model of a test vehicle in CMOS bulk technology with a TCAD model extracted from the package and the PCB layout. Each state of the power stage is studied separately to understand the link between parasitic components and the noise frequency spectrum. A similar approach is applied to the transition between these states in order to understand noise level dependency. Compared to measurements, the model gives a good and pertinent approximation of the noise key parameters leading to an understanding noise mechanism to design a safer power stage architecture.