7.3.2 Output Stage

LMG1025-Q1 provides 7-A source, 5-A sink (asymmetrical drive) peak-drive current capability, and features a split output configuration. The OUTH and OUTL outputs of the LMG1025-Q1 allow the user to use independent resistors connecting to the gate. The two resistors allow the user to independently adjust the turn-on and turn-off drive strengths to control slew rate and EMI, and to control ringing on the gate signal. For GaN FETs, controlling ringing is important to reduce stress on the GaN FET and driver. The output stage OUTL is also pulled down in undervoltage condition, which prevents the unintended charge accumulation of device Ciss, and thus preventing false turn-on. This ringing heavily depends on the layout as switching frequency increases and as rise and fall time gets shorter. The distance between the gate driver and power device need to be as minimum as possible. Gate loop should be as minimum as possible. If ringing is un-avoidable then the gate resistor should be selected in such a way that the ringing is minimized. Bypass capacitor type, value, and position also significantly affects this ringing.