As for all switching power supplies, especially those with high frequency and high switch current, printed-circuit board (PCB) layout is an important design step. If the layout is not carefully designed, the regulator can suffer from instability as well as noise problems. The following guidelines are recommended for good PCB layout.
- To prevent radiation of high-frequency resonance problems, use proper layout of the high-frequency switching path.
- Minimize the length and area of all traces connected to the SW pin and always use a ground plane under the switching regulator to minimize inter-plane coupling.
- The high current path, including the internal MOSFET switch, Schottky diode, and output capacitor, contains nanosecond rise times and fall times. Keep these rise times and fall times as short as possible.
- Place the VIN bypass capacitor as close to the VIN pin and the AGND pin as possible to reduce the IC supply ripple.
- Connect the AGND and PGND pins to thermal pad directly on the same layer.