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max232 [message #8969]

Fri, 06 August 2021 21:05

b1ackmai1er
Messages: 396
Registered: November 2017

Senior Member

Hello,

Where a board has 1uf capacitors for the max232, is it ok to replace it with a max232 that is designed for the 0.1uF capacitors?

Thanks.

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Re: max232 [message #8972 is a reply to message #8969]

Fri, 06 August 2021 23:56

trianon
Messages: 20
Registered: May 2020

Junior Member

From Maxim datasheet I found
MAX232 can handle 0.1u to 1.0uF
MAX232A is ony 0.1uF

https://datasheets.maximintegrated.com/en/ds/MAX220-MAX249.pdf

So it can work for a MAX232, not for an MAX232A.

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Re: max232 [message #8976 is a reply to message #8972]

Sat, 07 August 2021 10:16

just4fun
Messages: 273
Registered: May 2017
Location: Dark side of the Moon

Senior Member

If I remember well:

MAX232 -> 1uF
MAX232A -> 100nF but also 1uF.

NOTE: If you buy from ebay/aliexpress the MAX232 are ALL fake (but really cheap) but they can be used anyway in hobby projects if you use the "clamp trick" (using two schottky diodes) to avoid their typical latch-up with consequent over heating/burning (probably due to a "bad silicon copy") when connected to a powered RS232 before powering them... (see the MAX232 in my 68k-MBC schematic)... Laughing

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Re: max232 [message #8991 is a reply to message #8976]

Wed, 11 August 2021 07:14

b1ackmai1er
Messages: 396
Registered: November 2017

Senior Member

Thank you both. I tried reading the data sheet but really couldn't see the information I needed.
A lot of stuff seems to be "implied" in data sheets.

Time to revisit my RC-Z8BASIC board which had that very issue :0)

Regards Phil.

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Re: max232 [message #9007 is a reply to message #8991]

Thu, 12 August 2021 05:11

just4fun
Messages: 273
Registered: May 2017
Location: Dark side of the Moon

Senior Member

I've just checked the RC-Z8BASIC schematic (completely forgot this board...) and it has the "anti-latch-up" circuitry, so any "chinese" MAX232 (MAX232CPE) from ebay/aliexpress should work on it without "burning".

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Re: max232 [message #9011 is a reply to message #9007]

Thu, 12 August 2021 06:53

b1ackmai1er
Messages: 396
Registered: November 2017

Senior Member

The appropraite response here is drat, drat and double drat!

However, having said that, I a have learned a lot since I put that on the shelf, so time to do some debugging and get the logic analyser going Smile

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Re: max232 [message #9107 is a reply to message #9011]

Tue, 07 September 2021 02:10

just4fun
Messages: 273
Registered: May 2017
Location: Dark side of the Moon

Senior Member

@b1ackmai1er

Just to avoid to waste your time, I must warn you about the current "chinese" MAX232 availability.
Recently I've bought a new lot of "chinese" MAX232. Sadly these one are really garbage and completely unusable, causing any kind of oddity.
At this point is no more possible buy them on ebay/aliexpress as it is impossible to know if they are "working fake" (as the previous ones I bought in the past) or completely garbage.
So I've ordered some HIN232CPZ on TME. They are a more cheap equivalent of the MAX232CPE, and allow the use of both 0.1uF and 1uF capacitors as charge pump.

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Re: max232 [message #9108 is a reply to message #9107]

Tue, 07 September 2021 04:22

plasmo
Messages: 916
Registered: March 2017
Location: New Mexico, USA

Senior Member

I use MaxLinear's SP232E. The charge pump cap are 0.1uF to 10uF. It is cheap, too cheap to fake it. Unfortunately it is backordered at Mouser with long lead time. I have tubes of it, however, so I'm set for life.
Bill

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Re: max232 [message #9115 is a reply to message #9108]

Wed, 08 September 2021 15:17

b1ackmai1er
Messages: 396
Registered: November 2017

Senior Member

Sorry I did not see these additional replies.

YEs I think ordering a bulk order of one of these alternatives is a good idea, so this sore point does not have to be revisited again Smile

Best Wishes Phil.

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