The TPS2117 uses the highest voltage supply to power the device. When one supply drops below the other, the device changes the supply used to power the device. If the supply powering the device drops at a rate faster than 1 V/10 μs, the other supply must be at 2.5 V or higher to prevent the device from resetting. If the other supply is lower than 2.5 V, then the device may not be able to switch to the supply quickly enough, and the device will reset and turn on with soft start timing if VOUT < 1 V.