[FAQ] TPS65094: V5ANA and LDO5P0 Pin Load Switch

For typical applications, the LDO5P0 output pin is used to supply the 5V to power the controller drivers. The LDO5P0 output pin acts as a power path to ensure that the drivers are able to operate when 5V is not present, but to switch to the more efficient 5V source when it is present. To achieve this, the LDO5P0 pin is initially connected only to the LDO5 block which provides a regulated 5V supply from VSYS. Because VSYS can operate over a wide range, including up to 21 V, the LDO is not the most efficient 5V supply. Instead, as long as the external 5V supply is available at the V5ANA pin, the internal V5ANA-to-LDO5P0 load switch is enabled and the 5V external supply takes over for supplying the controller drivers.

The advantage of this approach is that the drivers can continue to operate even if the external 5V is unavailable. In most applications, this is not a requirement as the Braswell platform is designed to have the external 5V available as an always on rail. In such cases, the external 5V can be directly connected to the driver inputs.