How to optimize the ground and power layers of a smart controller PAC?

Optimizing the PCB ground and power layers of the intelligent controller PAC is crucial for EMC performance. The ground layer should be as intact as possible, avoiding splits. If splitting is unavoidable (e.g., analog/digital ground), the split gap should be less than 1mm, and a ferrite bead (e.g., PBZ1608A-102Z0T) should be connected across the split. Power and ground layers should be arranged adjacent to each other with a layer spacing of less than 0.2mm to form high-frequency decoupling capacitors. For multilayer boards, a symmetrical stack-up structure should be used (e.g., an 8-layer board: S1/GND2/S3/PWR4/GND5/S6/GN).

To reduce warpage and impedance discontinuities, decoupling capacitors (e.g., 0.1μF) are added across different power domains in the power layer segmentation region. Simulation tools (e.g., SIwave) are used to optimize the stack-up parameters to ensure that the characteristic impedance (e.g., 50Ω single-ended, 100Ω differential) and target impedance (e.g., <0.1Ω@100MHz) meet the requirements. After optimization, the power supply noise of the PAC is reduced by 40%, and the signal return path impedance is reduced by 50%, meeting the IEC61000-4-11 voltage sag immunity test.