power supply for external board

Hi,

I want to use the 3.3V of the FA to suppy an external board.
What is the maximal current I can use for the external board?

Best regards,
Markus

Look up the datasheet on the downloads page.  Then you'll have to either
measure the current going into the chip or the current coming out it.  They
should both be the same.  Subtract that from the max current spec at
whatever temperature you are going to operate the dev board at.

Then I would confirm it's temperature rise with a probe or your finger.

Personally, I would not tap into these supplies as accidents can happen. 
They help to isolate your expensive processor and other chips from a
potentially harsh 5Volt power supply environment.