The teensy receives 5V from the 7805 regulator. The 3.3V on the schematic is from the teensy. Teensy converts 3.3v from 5v input.
The micro requires more current to run the f9ps than is safe to pull from the teensy so it has a 7803 regulator to supply its power
Edit
Good information above on adding the regulators. BUT, make sure you remove the teensy and F9Ps before testing power after you solder the regulators in. This way you wont fry these expensive components if you have the regulators in backwards
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