On Sun, Jun 29, 2008 at 9:47 AM, Tom=E1s =D3 h=C9ilidhe <toe@lavabit.com> w=
rote:
>
> Let's say I have an LED with a Vf of 1.8 V and I want to put about 40 mA
> through it. The cathode goes straight to ground and the anode goes to a
> PIC pin.
>
> I can go from 5 V on the PIC pin, through a 80 ohm resistor into the
> LED, but of course the problem is that I'll be drawing more than the
> maximum current for a PIC pin.
>
> But I'm wondering if I could use two PIC pins together. Let's say I
> connect RD0 and RD1 together and then do the following in C code:
>
> PORTD |=3D 3u;
> TRISD &=3D ~3u;
>
> The idea would be that 20 mA would come from each pin.
>
> This a go-er?
>

I suppose, if you have extra pins.  You should use a separate resistor
from each pin, to help the current sharing.

PIC outputs don't behave like ideal switches when you're drawing
significant current from them.  I was schooled by a Microchip engineer
in this thread:

http://groups.google.com/group/pickit-devel/browse_thread/thread/2dd07bed31=
64d97c/7c076ab1e6e79583

Regards,
Mark
markrages@gmail
-- =

Mark Rages, Engineer
Midwest Telecine LLC
markrages@midwesttelecine.com

-- =

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