There are two types of current faults which can be detected by the driver: overcurrent fault and short-circuit fault.

The overcurrent protection (OCP) circuit monitors drain current and compares that current signal with an internally set limit I_T(OC). Upon detection of the overcurrent, the LMG365xR025 performs cycle-by-cycle protection as shown in Figure 8-2. In this mode, the GaN device is shut off when the drain current crosses the I_T(OC) plus a delay t_off(OC), but the overcurrent signal clears after the IN pin signal goes low. In the next cycle, the GaN device can turn on as normal. The cycle-by-cycle function can be used in cases where steady-state operation current is below the OCP level but transient response can still reach current limit, while the circuit operation cannot be paused. The cycle-by-cycle function also prevents the GaN device from overheating by overcurrent induced conduction losses.

The short-circuit protection is based on desaturation (de-sat) detection, which monitors the drain-source voltage V_DS and compares the voltage with an internally set limit V_T(Idsat). If the OC occurs before the de-sat, the V_DS is below the threshold, then OC is triggered, else de-sat is triggered as shown in Figure 8-3. Saturation can be damaging for the GaN to continue to operate in that condition. Therefore, if a de-sat is detected, the GaN device is turned off with an intentionally slowed driver so that a lower overshoot voltage and ringing can be achieved during the turn-off event. This fast response circuit helps protect the GaN device even under a hard short-circuit condition. In this protection, the GaN device is shut off and held off until the fault is reset by either holding the IN pin low for a period of time defined in the Specifications or removing power from VDD.

For safety considerations, OCP allows cycle-by-cycle operation while de-sat latches the device until reset. Both faults are reported on the FLT/RDRV pin.