[Mike Copioli]

Originally Posted by marcan

I just tested my OI to 100mA from Port 1 Aux (pins 1 and 4) running two (overloaded) white LEDs. Multimeter measures 100mA, voltmeter measures 4.5V. Okay, so the voltage does drop a bit, but I intend to run 3.3V circuitry using a switching buck regulator anyway, and 4.5V will still work fine for most 5V ICs too. My calculations say worst-case the aux circuits will draw 100mA at 3.3V, which is 66mA at 4.5V and 60mA at 5V (remember, this is a switching regulator, not a linear one, so it ideally does not waste any power). Even with some extra stuff thrown in (LEDs, DC-DC inefficiency, etc), I still have room.

You may get lucky for about a minute of continuous use, but I assure you you will be operating the O/I out of spec. A good design sould be created so that it meets the specs called out by the data sheets and operational specifications. If your TOTAL current consumed by ALL 5v AUX pins is greater than 100mA you run the risk of the voltage being clamped to 300mV.
We have done extensive testing with the O/I and this does happen.