MAX 3232 gets hot - Page 1
Forum section: electronics / beginners

author: TinkeringSteve
author_rank: Frequent Contributor
timestamp: July 26, 2018, 06:23:45 pm
content: Hey there!I got some of those little max3232 modules:Symptoms now:PCB gets hot, draws over 100mA, communication does not work.Supposed setup:A devboard which uses 3.3V I/O voltage is connected to the "TTL" side of the board. Both boards are on a bigger perfboard with some wiring underneath, connected through pin headers.The "RS232" side of the board is connected to a plug that connects an industrial device with a RS232 port.What I did:At first, I soldered everything as I supposed it should go, but that didn't work. (no docs were offered, and at first, I found nothing online, so I guessed).Turns out "arrow points to pin" does not mean it's RX because data flows into the pin...On the 3V3 devboard side, TX and RX were mixed up, on the 232 side I did it right by mistakePerhaps that's a first possible point of damage (TX fighting TX) - but the second board did not need this to show the same symptoms, with the difference that it never worked, unlike the first board which, theoretically, got more abuse.Since the header pads are not particularly clearly labeled, and my first guess was wrong, I prodded on them IC pins vs. header pins with a DMM, which on most settings outputs < 1V, on some settings 1.8V.Could I have damaged the IC in a way that makes it not necesarily fail immediately, but after a while?Could they be fake ICs which are more susceptible to "conditions" making them break easily?It's interesting that a stock photo of the max3232 has 3 parallel fine lines marking the "1" end of the IC, whereas mine has one thick blurry line (cheaper printing?)Anyway, after swapping TX,RX on the "TTL" side, it worked for 10 minutes or so, communication in both directions @ 115200 no problem.Then later it did not work anymore, and I noticed the higher current consumption, and the PCB module was cup-of-coffee-ish hot in one small spot (could only touch the underside, not the IC).I thought, ok, maybe it was the initial TX vs TX and swapped the module with another one - which immediately displayed this behavior: No communication, high current drawing, and rising temperature.Let me mention that it's very warm right now, maybe 35°C. No match for Chinese summer I reckon.I measured the pins: nothing over the 3.4V that comes as supply from the devboard on the "TTL" side, and the RS232 side had one pin at -5V and another at +2V or so.The RS232 side "+" pin also measures 3.4V, not sure of purpose, but in some Chinese sites with diagrams I now found, that pin is unused, so it's open here.EDIT:Also interesting: my prodding with DMM wasn't so successful, e.g. the VCC pin, according to datasheet, did not connect to the "+" pin on the module... but the chinese site I found did say that's the +3V3 pin. Other pins also showed no direct connection.Any ideas what the heck could be going on?

author: Cliff Matthews
author_rank: Unknown
timestamp: July 26, 2018, 09:06:17 pm
content: There's fakes aplenty from China (some chip versions suffer from latch-up). Member AllTheGearNoIdea did a fun video on it..*edit - Found the episode, it's 31mins so here's the indexhttps://youtu.be/mNsLj6gleQs?t=1011

author: Kentarrio
author_rank: Newbie
timestamp: July 26, 2018, 09:30:19 pm
content: Sounds like classic China hardware unfortunately. At least they're cheap

author: wraper
author_rank: Unknown
timestamp: July 26, 2018, 09:32:40 pm
content: There are already several threads about counterfeit RS-232 drivers/receivers heating up.https://www.eevblog.com/forum/reviews/fake-max3232-any-additional-details/https://forums.overclockers.com.au/threads/max3232-cooking-a-bad-chip.1154470/

author: Cliff Matthews
author_rank: Unknown
timestamp: July 26, 2018, 09:41:54 pm
content: Thanks wraper, I knew we had chats over that, it's been a while.. Buyers beware, China strikes again!

author: NivagSwerdna
author_rank: Super Contributor
timestamp: July 26, 2018, 10:12:25 pm
content: Welcome to the clubhttps://www.eevblog.com/forum/chat/fake-chips/msg1552951/#msg1552951

author: TinkeringSteve
author_rank: Frequent Contributor
timestamp: August 22, 2018, 11:39:19 am
content: Update: Ok, bought the IC new from a known German seller, and it just works as supposed