Use a four-layer or six-layer PCB for good
thermal performance and with maximum ground plane.
3-inch × 3-inch, four-layer PCB with 2-oz copper
is used as an example.
VIN, PGND, and SW traces must be
as wide as possible to reduce trace impedance and improve heat dissipation.
Place equal capacitors on each
side of the IC. Place them right from each VIN to PGND pin as close as possible
to the device on the same side of the PCB.
Use vias near both VIN pins and
provide a low impedance connection between them through an internal layer.
Use multiple vias near both PGND
pins and use the layer directly below the device to connect them together, which
helps to minimize noise and can help heat dissipation.
Inner layer 1 is ground with the
PGND to AGND net tie.
Inner layer 2 has VIN copper pour that has vias
to the top layer VIN.
Bottom layer is GND with the BOOT
trace routing.
Reference feedback to the quiet
AGND and route away from the switch node. Also keep feedback resistors and the
feedforward capacitor near the IC.