Layout is a critical portion of good power
supply design. Key guidelines to follow for the
layout are:
- Make VIN, PGND, and SW traces as wide as possible
to reduce trace impedance and improve heat
dissipation. Use vias and traces on others layers
to reduce VIN and PGND trace impedance.
- Use multiple vias near the PGND pins and use
the layer directly below the device to connect
them together, which helps to minimize noise and
can help heat dissipation
- Use vias near both VIN pins and provide a low
impedance connection between them through an
internal layer.
- Place the smaller value high frequency bypass
ceramic capacitors from each VIN to PGND pins and
place them as close as possible to the device on
the same side of the PCB. Place the remaining
ceramic input capacitance next to these high
frequency bypass capacitors. The remaining input
capacitance can be placed on the other side of the
board but use as many vias as possible to minimize
impedance between the capacitors and the pins of
the IC.
- Route FB traces away from the noisy switch node.
Place the bottom resistor in the FB divider as
close as possible to the FB pin of the IC. Also
keep the upper feedback resistor and the
feedforward capacitor near the IC. Connect the FB
divider to the output voltage at the desired point
of regulation.
- Place the BOOT-SW capacitor as close as possible
to the BOOT and SW pins.