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From: | Graham Davies |
Subject: | Re: [avr-chat] STK500 LEDs |
Date: | Tue, 16 Oct 2007 19:31:35 -0400 |
Gavin Jackson wrote:
This is the standard way for driving LEDs, the micro can sink more current than it can source ...
This isn't really true. From the data sheet of the ATmega16, for instance, you can see that the outputs can source very nearly as hard as they can sink. In my opinion, this low-for-ON choice is a harmless holdover from the days of TTL current sinking logic when outputs could most definitely sink more than they could source (hence "current sinking"). As CMOS took over from TTL, threshold levels were retained for compatibility and the designs of the output stages were quite artificially warped towards current sinking. Today, however, you will often find outputs to be powerful sources of current as well as sinks.
Graham.
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