VIN_3V3 takes precedence over VBUS, meaning that when both supply voltages are present the TPS65988 powers from VIN_3V3. See Figure 8-9 for a diagram showing the power supply path block. There are two cases in which a power supply switch-over occurs. The first is when VBUS is present first and then VIN_3V3 becomes available. In this case, the supply automatically switches over to VIN_3V3 and brown-out prevention is verified by design. The other way a supply switch-over occurs is when both supplies are present and VIN_3V3 is removed and falls below 2.85 V. In this case, a hard reset of the TPS65988 is initiated by device firmware, prompting a re-boot.