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 Protect a MAX232 from PIC programming high voltage

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T O P I C    R E V I E W
Fonggong Posted - 05/18/2017 : 23:45:02
I want to be able to reset a PIC remotely using the only communication port of the board, the RS232. But I also want to be able to program it using a ICD3 (no bootloader), and this programmer apparently applies high voltage (0-13V?) to /MCLR which will certainly kill the MAX232(MAX233 in fact).

Would a schottky between R2out of the MAX233 and 5V be the way to go? The datasheet says that the absolute maximum voltage on that pin is 5.3V, I find it a bit tight for a schottky. Any more robust suggestions? I don't want to use a jumper as this could be forgotten...

Schematic:

7   L A T E S T    R E P L I E S    (Newest First)
supervizeur Posted - 06/12/2017 : 11:17:50
quote:
Originally posted by anniel

quote:
Originally posted by supervizeur

Successful?



We may never know.



Probably.
anniel Posted - 06/09/2017 : 06:29:33
quote:
Originally posted by supervizeur

Successful?



We may never know.
supervizeur Posted - 06/04/2017 : 02:54:14
Successful?
anniel Posted - 05/29/2017 : 09:31:09
Did they try???
supervizeur Posted - 05/29/2017 : 07:27:51
Yes a Zener should be good.
anniel Posted - 05/19/2017 : 05:35:00
A Zener should do the trick.
Fonggong Posted - 05/18/2017 : 23:46:56
More details about MAX232 here: www.kynix.com/Detail/581629/MAX232.html

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