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Altera_Forum's avatar
Altera_Forum
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16 years ago

led driving capability of a CPLD I/O pin when increasing track length in pcb.

Hi Guys, I want to drive a very large LED matrix(used in a big LED display board) with the help of MAX3000 family CPLD. I have a question in my mind: Basically,I know that I can drive an LED t...
Altera_Forum's avatar
Altera_Forum
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16 years ago

Well how long of a PCB trace are we talking here? Basically the only factor is the effective resistance of the PCB trace. I don't have my equation handy but you'd have to have a pretty long trace for this to make any difference at all.

Here is a calculator:

http://www.referencedesigner.com/cal/cal_05.php

You can use this to estimate the resistance of the trace and then figure how this affects the current through the diode.

Jake