Hi,
He shouldn't use 7805 at all! If you he uses 7805 with 28V input voltage (assuming that 28V input is acceptable for 7805) , it will dissipate 23W at 1A output current. It will need a very large heat-sink or it will shutdown itself.
@OP: as KlausST stated , PGD Pin is open drain. you should a pull-up resistor and connect the pull-up resistor to the microcontroller power supply (5V).
as for 5V -1A supply , you can also use LM2576 , it has better footprint for connecting it to any heat-sink and also has a 5V model, so your external components will be minimum (only 4 components).