Displayed here is the circuit for the 240W design. The engineer is using an external LDO in order to boost the efficiency. If the 5V source is available, one can depopulate the LDO. The ISL8117 will automatically switch to internal LDO mode and take care of it. If the output is 5V, then just connect the output to this pin and the ISL8117 will self-bias itself from its own output.