Small gate capacitance and Miller capacitance enable enhancement mode GaN FETs to operate with fast switching speed. The induced high dv/dt and di/dt, coupled with a low gate threshold voltage and limited headroom of enhancement mode GaN FETs gate voltage, make the circuit layout crucial to the optimum performance. Following are some recommendations:

1. Place the GaN FETs as close as possible to the gate driver. The main priority of the layout is to decrease overall loop inductance and to minimize noise coupling issues by confining the peak currents that charge and discharge the GaN FET gates to a minimal physical area on the printed circuit board.
2. Minimize the loop area of the bootstrap charging path as it can contain high peak currents. Given that the TPS7H60x5 has multiple bootstrap charging options, and that the charging takes place on a cycle-by-cyle basis, place both the bootstrap capacitor and diode to facilitate a small loop area for the chosen charging method.
3. Place all bypass capacitors (VIN to AGND, BP5L to AGND, BP5H to ASW, BOOT to ASW) as close to the device and respective pins as possible. Capacitors with low ESR and ESL are recommended. If possible, place these capacitors on the same side of the printed circuit board as the gate driver.
4. Separate power traces and signal traces and minimize any overlap of the signals on different printed circuit board layers.
5. The parastic inductance in series with the source of the high-side FET and the low-side FET can impose excessive negative voltage transients on the driver during switching. Use short, low-inductance paths to connect PSW to the high-side FET souce, and PGND to the low-side FET source.
6. To prevent excessive ringing on the input power bus, good decoupling practices are required by placing low-ESR capacitors adjacent to the GaN FETs.