If you look a little closer at the spec you will find that the IO's 
are specified at 8.5mA for Vol and 3.5mA for Voh with 25mA being the 
absolute max (and 200mA per port).  What you will find is that the 
series resistance of the IO transistors (about 40-70 Ohms) will cause 
your output to droop.  With 20mA of current and ONLY 40 Ohms of 
resistance the output will be about 800mV lower.  This may not effect 
your design, and in many cases it does not, but you need to be aware.

Phil

mchristisen wrote:

>Ok, did some more looking. Forward Voltage rating is the voltage drop. So if
>I have a 1.6V LED and a 5V source I subtract 1.6 from 5 and divide by the
>current rating to find that I need a 170ohm resistor. Damn, feel like an
>idiot on that one.
>
>
>So, do I run a PIC output close to its max. sink rating (25mA in my case) to
>direct drive an LED at 20mA or should I increase the resistor to get around
>15mA?
>
>--
>View this message in context: http://www.nabble.com/-PIC-Driving-LED%27s-%28newbie-%29-t1176852.html#a3095886
>Sent from the MicroControllers - PIC forum at Nabble.com.
>
>  
>


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