8.2.2.1 Gate Drive Supply Voltage

The drive voltage for GaN FETs must be tightly regulated, that’s why a linear regulator is integrated in UCC27611 to providing well-regulated 5-V voltage (VREF). Depending on layout and noise generated by the power stage, the parasitic inductance in conjunction with the Miller capacitance of the FET can cause excessive ringing on the gate drive waveform resulting in peaks higher that the regulated VREF drive voltage. With enough energy present, the potential exists to charge the VREF decoupling capacitor higher than the 6-V maximum allowed on a Gallium Nitride transistor. To prevent this from happening, the driver must be close to its own FET to avoid excessive ringing during fast switching transitions, and external gate resistor R_GH connected to OUTH pin of driver must be used to limit the turnon speed.