The drain pads are used for dissipating heat from the two power paths. DRAIN1 and DRAIN2 should NEVER be connected to each other or to GND. They should be left floating with their own nets assigned. The top layer should have all of the DRAIN1 pins tied to the DRAIN1 pan and the DRAIN2 pins tied to the DRAIN2 pad. When high currents are expected in the system it is recommended to place “fins” on the DRAIN1 and DRAIN2 pads. The effective heat dissipation distance is roughly 3 mm from the pad so it does not have to extend to a large area. Figure 11-15 shows the top layer routing for DRAIN1 and DRAIN2.

Figure 11-15 DRAIN1 and DRAIN2 Top Layer

On the bottom layer DRAIN1 and DRAIN2 pour are also required and it is recommended to have a larger pour than the DRAIN1 and DRAIN2 pads. The bottom layer will provide most of the heat dissipation and space should be reserved for the pours. Figure 11-16 shows the bottom layer routing for the DRAIN1 and DRAIN2 pads.

Figure 11-16 Figure 13. DRAIN1 and DRAIN2 Bottom Layer