SLVSEW8B August 2019 – December 2019 TPS66020 , TPS66021
PRODUCTION DATA.
Figure 18 shows the typical power up sequence during a dead battery condition. During a dead battery condition, the TPS6602x is internally powered by the VBUS LDO. The VBUS LDO may be used to supply a limited amount of current for use in the system during dead battery, such as supplying power to a PD controller. In this case, it is assumed the VLDO terminal is providing power to a PD controller that is controlling the TPS6602x. Once VIN is stable, the VLDO terminal switches from being supplied by the VBUS LDO to being supplied by the VIN terminal, and the VBUS LDO is automatically disabled. The switch over process is completely seamless.
NOTE
Switching from VBUS LDO operation to VIN operation is seamless and no device reset will occur. When switching from VIN power to VBUS LDO operation, the switch over circuitry will attempt to switch over to the VBUS LDO, however it is not assured that the VLDO level will be maintained above the VLDO UVLO threshold. In this case, a device reset may or may not occur.