There are two overtemperature shutdown thresholds in the part. The first one measures the GaN die temperature and trips around 165 °C. When it trips, the power IC disables switching and asserts the FAULT pin, but maintains the buck-boost and external LDO. During the overtemperature shutdown, the GaN device is held off until the temperature falls below the hysteresis limit, typically 20 °C below the turn-off threshold. This is not a latched protection scheme. In most applications, disabling the switching will allow the device to cool off. However, if there is instead a short circuit in the VNEG rail or the external 5-V LDO, the driver die temperature will continue to rise. If the silicon driver die temperature exceeds 185 °C, it will also shut down the buck-boost and the external LDO.
If the GaN die is over 165 °C and the overtemperature shutdown is active, but the driver is not over 185 °C where the buck-boost shuts down, the part will operate as an ideal diode that ignores the input and turns on and off automatically when it detects third-quadrant current. This is to lower the power dissipated in the GaN in third-quadrant operation.