Use a four-layer PCB with maximum ground plane partitioning possible for good thermal performance. A 76mm × 76mm, four-layer PCB with 2-1-1-2 oz copper is used as example.
Make VIN and PGND traces as wide as possible to reduce trace impedance. The wide areas are also of advantage from the view point of heat dissipation.
Put at least two vias for PGND pad for better thermal performance.
Place the input capacitor and output capacitor as close to the device as possible to minimize trace impedance.
Provide sufficient vias for the input capacitor and output capacitor.
Keep the SW trace as physically short and wide as practical to minimize radiated emissions.
Do not allow switching current to flow under the device.
Keep the SS trace as far as possible to SW trace to minimize coupling during soft start.
Connect a separate VOUT path to the upper feedback resistor.
Keep the voltage feedback loop away from the high-voltage switching trace, and preferably has ground shield.
Make the trace of the VFB node as small as possible to avoid noise coupling. Also keep feedback resistors and the feedforward capacitor near the IC.
Make the PGND trace between the output capacitor
and the PGND pin as wide as possible to minimize the trace impedance.
Note that inner layer 1 is PGND and AGND with the
single point net tie.
Note that inner layer 2 is PGND for better heat
dissipation.