AVR-Chat

On Tue, Nov 18, 2008 at 09:38:50AM -0500, David VanHorn wrote:
> On Tue, Nov 18, 2008 at 7:11 AM, Kathy Quinlan
> <kaqdialup@iinet.net.au> wrote:
> > NO, the internal diodes are not designed for this level of
> > protection, depending on your external resistor values, you could
> > exceed the maximum sink current of the device.
> 
> Definitely correct.  Although the internal protection diodes exist,
> you are never supposed to use them.

People these days tend to forget The Bad Old Days when most every IC was
super sensitive to static discharge during handling. They are still
sensitive but not anything nearly as bad as they once were when one
could almost zap gates with ESP (Extra-Sensory Perception, just by
thinking).

There is/was an Atmel appnote on building an electric power meter where
240 VAC was connected directly to an input pin through a 1 or 10 megohm
resistor, stating the protection diode was safe up to 1 mA. And then the
appnote went to lengths disavowing the safety ...

-- 
David Kelly N4HHE, dkelly@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.