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 Protect a MAX232 from PIC programming high voltage
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Fonggong

2 Posts

Posted - 05/18/2017 :  23:45:02  Show Profile  Reply with Quote
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:

Reply #1

Fonggong

2 Posts

Posted - 05/18/2017 :  23:46:56  Show Profile  Reply with Quote
More details about MAX232 here: www.kynix.com/Detail/581629/MAX232.html
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Reply #2

anniel

2403 Posts

Posted - 05/19/2017 :  05:35:00  Show Profile  Reply with Quote
A Zener should do the trick.
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Reply #3

supervizeur

462 Posts

Posted - 05/29/2017 :  07:27:51  Show Profile  Reply with Quote
Yes a Zener should be good.
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Reply #4

anniel

2403 Posts

Posted - 05/29/2017 :  09:31:09  Show Profile  Reply with Quote
Did they try???
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Reply #5

supervizeur

462 Posts

Posted - 06/04/2017 :  02:54:14  Show Profile  Reply with Quote
Successful?
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Reply #6

anniel

2403 Posts

Posted - 06/09/2017 :  06:29:33  Show Profile  Reply with Quote
quote:
Originally posted by supervizeur

Successful?



We may never know.
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Reply #7

supervizeur

462 Posts

Posted - 06/12/2017 :  11:17:50  Show Profile  Reply with Quote
quote:
Originally posted by anniel

quote:
Originally posted by supervizeur

Successful?



We may never know.



Probably.
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