When is a 74HC595 not a 74HC595...? - Page 1
Forum section: electronics / projects

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 16, 2022, 10:53:54 pm
content: .. when it comes from "Shenzen Fine Mad Electronics".https://lcsc.com/product-detail/Registers_Shenzhen-Fuman-Elec-74HC595A_C110383.html1) No /enable pin2) No /SRCLR pin ( not that this was ever any use as it doesn't clear the output latch )3) OPEN DRAIN OUTPUTS!.....SO DON'T CALL IT A BLOODY 74HC595 then!The Chinese version of LCSC does warn of this, in Chinese...https://item.szlcsc.com/111606.htmlThere are 74HC595s from TEN different obscure Chinese manufacturers on LCSC, in addition to six big-name brands.Unfortunately that wierd-ass one is a fraction of a cent cheaper so appears first in the "sort by price" list.Guess which one I just populated 650 of on a batch of boards....Oh well it could have been worse, I also just did a batch of boards with a total of 2400 HC595s in SSOP packages, luckily TI had stock when I ordered those...

author: CaptDon
author_rank: Super Contributor
timestamp: July 16, 2022, 11:05:50 pm
content: Ch-Ch-Ch-China!!!! Wonder if we pour water on all the defective and fake Chinese knockoff stuff it would grow green hair like a chia-pet??? Oh let me just try to count the many ways I hate our communist enema......opps, I mean enemy!!!

author: moffy
author_rank: Super Contributor
timestamp: July 16, 2022, 11:07:08 pm
content: That is a ridiculous gotcha, it isn't the same part. We used to have problems sometimes with purchasing substituting a cheaper part for one that was specified by manufacturer, the problem was that not all of the characteristics we needed were covered by the parts sheet and different manufacturers produced slightly different parts. Could lead to real problems in production.

author: Benta
author_rank: Super Contributor
timestamp: July 16, 2022, 11:07:33 pm
content: Well, you've learned the lesson of being a cheapskate. Go cry somewhere else.Reliable supply channels are the life and blood of preofessionals and industry.But perhaps they'll send you a complimentary pair of chopsticks next time.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 16, 2022, 11:14:56 pm
content: Quote from: Benta on July 16, 2022, 11:07:33 pmThis was not about cost - at the time of ordering there was no stock of name-brands at Digikey or elsewhere. I'd have happily ordered Diodes, Onsemi etc. if they had been available.9 out of the 10 parts from obscure LCSC brands at similar prices would have been fine - I've used 74HC595s and plenty of other other parts from LCSC in the past with no problems.Can you honestly say that you would have checked the manufacturer's datasheet for a 74HC part just to make sure it wasn't different to the same part from every other manufacturer?

author: IanJ
author_rank: Unknown
timestamp: July 16, 2022, 11:19:53 pm
content: Some kind of 74HC164 / 595 hybrid from China......help ma boab!

author: moffy
author_rank: Super Contributor
timestamp: July 17, 2022, 02:35:13 am
content: Quote from: mikeselectricstuff on July 16, 2022, 11:14:56 pmYes the current semi shortage is a real issue.

author: Buriedcode
author_rank: Super Contributor
timestamp: July 17, 2022, 04:11:42 am
content: It's particularly egregious as it really does have the 74HC in the part number, rather than a seperate prefix like other "similar parts but with more specific applications" have. The entire point of certain part number prefixes is that its standardised so one *doesn't* have to check the datasheet for every spec or the pinout.When I first read the post I thought mike had just got some chips that were claimed to be compatible but had a different part number. And as he points out, the current state of part sourcing makes one have to venture further away from tried-and-true/trusted sources. A tru gotcha this one.

author: uer166
author_rank: Super Contributor
timestamp: July 17, 2022, 04:19:15 am
content: Quote from: Benta on July 16, 2022, 11:07:33 pmI'm not sure you know who Mike is or the scale of his projectsYou must be fun at partiesSeriously, I get that you're supposed to go through every datasheet of the part 100%. But if there's no English version and the PN matches a defacto standard partexactly, not having functional compatibility in a nominal case is a valid complaint. I don't expect these to have the exact same propagation delays or temp stability, but deleting pins and changing I/O type to the point where it would never work unless explicitly designed in is a valid complaint.

author: voltsandjolts
author_rank: Unknown
timestamp: July 17, 2022, 08:01:57 am
content: Quote from: mikeselectricstuff on July 16, 2022, 10:53:54 pmI do wonder if they intended their english name to be "Shenzen FineMadeElectronics" but the translation went awry......and they ended up with something much more appropriate

author: wraper
author_rank: Unknown
timestamp: July 17, 2022, 08:17:42 am
content: Quote from: voltsandjolts on July 17, 2022, 08:01:57 amYes it is. In this variant of HC595 datasheet they got their name properlyhttps://datasheet.lcsc.com/lcsc/2201121500_Shenzhen-Fuman-Elec-74HC595D-_C2929943.pdf

author: tooki
author_rank: Super Contributor
timestamp: July 17, 2022, 01:06:26 pm
content: In all fairness, adding the “A” to the part number as they did is a perfectly valid way of distinguishing a similar, but not identical part. I mean, single-letter suffixes frequently hide significant differences, even within a manufacturer.

author: wraper
author_rank: Unknown
timestamp: July 17, 2022, 01:37:17 pm
content: Quote from: tooki on July 17, 2022, 01:06:26 pmThe problem is that many other manufacturers have normal HC595 with "A" suffix too. As it's intended for driving LED, adding "LED" or at least a single letter suffix which is not commonly used would be OK-ish so there is at least suspicion you need to look into datasheet. Not to say they sell 74HC595D with exactly the same issue and "D" normally indicates package type.https://datasheet.lcsc.com/lcsc/2201121500_Shenzhen-Fuman-Elec-74HC595D-_C2929943.pdfAnother one got bit by this garbagehttps://forum.arduino.cc/t/74hc595a-shift-register-low-level-output/700036I would call this "part number search terrorism"

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 17, 2022, 02:58:14 pm
content: Quote from: tooki on July 17, 2022, 01:06:26 pmonsemi and TI also use an -A suffix for the standard part

author: Kleinstein
author_rank: Super Contributor
timestamp: July 17, 2022, 03:45:57 pm
content: Using the same name as a standard part and than providing a somewhat different functionality is really not nice, but it did happen before.There are some 74 series gates which depending on the manufacturer have an additional inverted output or not. AFAIR the RCA version of the 7430 had an extra output - at least there the extra function was for the non standard one.For the 74LV4053 I just found that the Ti and Nexperia version are somewhat different:The nexperia version has about 2-3 x the on resistance and an additional level shifter/ negative supply like the 74HC4053.It just "released" (hardly available) TL072H, which is quite different from the normal TL072 - not a bad part, but with a deceiving name.Another nasty one are LM321 - there is an old (long obsolete) original, that is not a single OP.

author: tooki
author_rank: Super Contributor
timestamp: July 17, 2022, 04:36:46 pm
content: Quote from: mikeselectricstuff on July 17, 2022, 02:58:14 pmOh. In that case, then yeah, it’s just a dick move to use the same part number.

author: bd139
author_rank: Super Contributor
timestamp: July 17, 2022, 07:30:59 pm
content: Oh that's one hell of a shit show. Thanks for posting the details. LCSC added to the shitlist now.

author: wraper
author_rank: Unknown
timestamp: July 17, 2022, 07:32:44 pm
content: Quote from: bd139 on July 17, 2022, 07:30:59 pm

author: floobydust
author_rank: Super Contributor
timestamp: July 17, 2022, 07:49:26 pm
content: I like how they saved micropennies omitting bonding wires, for the boss's new Lambo.chinese don't know the difference between a part number, model number, revision number, series number - it's all a blur mixed with scam.But no excuse to bastardize the 74HC595 as a standard part. I do see LCSC offering bottom rung junk sometimes.

author: wraper
author_rank: Unknown
timestamp: July 17, 2022, 08:10:31 pm
content: Quote from: floobydust on July 17, 2022, 07:49:26 pmIt's obviously a different die, not just missing bond wires.

author: bd139
author_rank: Super Contributor
timestamp: July 17, 2022, 08:12:52 pm
content: Yep and I’m sure they saved 2 attobucks polluting the market with this shit.

author: wraper
author_rank: Unknown
timestamp: July 17, 2022, 08:24:32 pm
content: Quote from: bd139 on July 17, 2022, 08:12:52 pmWell, it's a legit part which has its uses. In the datasheet it says it's for driving LED displays and in many of such cases it indeed can be used as drop-in replacement for 74HC595. Obviously they kept the usual part number for exposure, but WTF to make exactly the same part number as normal 74HC595 is beyond me.

author: SL4P
author_rank: Super Contributor
timestamp: July 17, 2022, 11:11:55 pm
content: Whenever we stumble across these things, All the engineers share the news, gather round the coffee machine, raise our mugs and cheer… “CHINA BEST” !

author: jonpaul
author_rank: Super Contributor
timestamp: July 18, 2022, 01:07:36 am
content: You get what you pay for.Chinese IC =junk, waste of time and moneyj

author: bd139
author_rank: Super Contributor
timestamp: July 18, 2022, 07:19:17 am
content: To be fair there’s nothing wrong with China as long as you don’t buy anything designed there and don’t buy anything manufactured there that hasn’t been validated somewhere that isn’t there

author: Hiemal
author_rank: Regular Contributor
timestamp: July 20, 2022, 08:02:36 am
content: Lesson learned today too actually. The CJ431 shunt regulator that JLCPCB has on their "basics" part list, does NOT follow the standard TL431 pinout. It's a TL432 flavor style with the ref and cathode pins swapped. Took too much time trying to diagnose and troubleshoot a power supply when the entire issue is the shunt regulator not working properly. Go figure.

author: gamalot
author_rank: Super Contributor
timestamp: July 20, 2022, 08:51:52 am
content: Quote from: Hiemal on July 20, 2022, 08:02:36 amCJ431 is not particularly bad, at least not worse than P2N2222.