Designing for high power density requires consideration of noise coupling and thermal management. A four-layer PCB structure is highly recommended to use inner layers to help reduce current-loop areas and provide heat-spreading for surface-mount semiconductors.

• Provide internal-layer copper areas to improve heat dissipation of high-power SMDs, particularly for switching MOSFETs and power diodes. Use multiple thermal-vias to conduct heat from outer pads to inner-layers and supporting copper areas.
• To avoid capacitive noise coupling, do not cross outer-layer signals over copper areas that carry high-frequency switching voltage.
• To avoid inductive noise coupling, keep switching current loops as small as possible, and do not run signal tracks in parallel with such loops.
• Arrange the conducted-EMI filter components such that they do not allow switching noise to bypass them and affect the input. Avoid running switching signals through the EMI filter area.
• Use multiple vias to connect high-current tracks and planes between layers.

Figure 11-1 summarizes the critical layout guidelines, and more detail is further elaborated in the descriptions below.

Figure 11-1 Typical Schematic with Layout Considerations