Good Design versus what (usually) works - Tutorial / was ...
Jim Hartmann email (remove spam text)
I think its all a matter of what you expect your circuit to see. Adding
external SOT23 Schottky diodes may be no better than relying on the
internal "diodes", the current still must be limited by some means. The
SOT23 blowing up is no better than the PIC blowing up. The SOT23 has
current limit X, the internal diodes have limit Y. The internal "diodes"
are sufficient if I can guarentee a current limit significantly less than Y
(keeping in mind that the Abs Max Voltage spec. must also be met).
David Bengtson <POBOX.COM>MITVMA.MIT.EDU> on 10/11/1999 08:37:30 dbengtson
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Subject: Re: PICs: Good Design versus what (usually) works - Tutorial /
On Sun, 10 Oct 1999 17:15:10 +1300, in you wrote:
>Agree fully. But this problem may occur if resistors alone are used.
>> The very very minute cost of either diodes, transistors, or buffers
>> ICs is just not worth destroying your project.
>Yes. As someone noted, such costs may be not insignificant in volume
>production but must still be considered.
Just a quick comment here. Even though it may seem silly to have $1.00
in protection components protecting a $0.50 microprocessor, you should
also keep in mind the cost of failure. If that $1.00 in protection
stops a field service call at $500, then perhaps it is worth it. Even
more important, if your products develop a reputation for being
unreliable, your in really deep doo-doo.
See also: www.piclist.com/techref/microchip/devices.htm?key=pic
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