The performance of switching converters heavily depends on the quality of the PCB layout. The following guidelines will help users design a PCB with the best power conversion performance, thermal performance, and minimize generation of unwanted EMI.
- Put the Q1, D1, and RS components on the board first.
- Use a small size ceramic capacitor for COUT.
- Make the switching loop (COUT to D1 to Q1 to RS to COUT) as small as possible.
- Leave a copper area near the D1 diode for thermal dissipation.
- Put the device near the RS resistor.
- Put the CVCC capacitor as near the device as possible between the VCC and PGND pins.
- Use a wide and short trace to connect the PGND pin directly to the center of the sense resistor.
- Connect the CS pin to the center of the sense resistor. If necessary, use vias.
- Connect a filter capacitor between CS pin and power ground trace.
- Connect the COMP pin to the compensation components (RCOMP and CCOMP).
- Connect the CCOMP capacitor to the power ground trace.
- Connect the AGND pin directly to the analog ground plane. Connect the AGND pin to the RUVLOB, RT, CSS, and RFBB components.
- Connect the exposed pad to the AGND pin under the device.
- Connect the GATE pin to the gate of the Q1 FET. If necessary, use vias.
- Make the switching signal loop (GATE to Q1 to RS to PGND to GATE) as small as possible.
- Add several vias under the exposed pad to help conduct heat away from the device. Connect the vias to a large ground plane on the bottom layer.