what is a MM5422N ? - Page 1
Forum section: electronics / general

author: Martin.M
author_rank: Frequent Contributor
timestamp: December 21, 2020, 08:21:25 am
content: I want to know please what exactly is a MM5422N ? bec. I have a bunch of them, no datashs, nothing.thank you

author: tooki
author_rank: Super Contributor
timestamp: December 21, 2020, 11:00:30 am
content: Could they be the ones mentioned in this PDF?https://media.searchelec.com//specshee/NATIONAL/NationalSemiconductorOptoelectronicsHandbook1979_text.pdf(too big to attach)

author: ebastler
author_rank: Super Contributor
timestamp: December 21, 2020, 11:44:57 am
content: It would have helped to know whether the mystery part is indeed a 22-pin DIL package."Digital alarm clock", and while the databook does include a block diagram, it does unfortunately not show a pinout. Hope the OP does not have too many of these on the shelf...

author: Martin.M
author_rank: Frequent Contributor
timestamp: December 21, 2020, 05:22:08 pm
content: thank you,hard to find a application for thatI have some of them, also some 5457is a 5422N a 5457 in another DIL package?they are both alarm clocks, hours + minutes, no seconds.I am searching for a application to sold a alarm clock from that, just for fun.Importat to me is what kind of LED display is used there , what they mean "duplex display"? At best the complete datasheet + application from NS.f you want one of them I can send it in a envelope :-) here are 18 pcs 5422 and 18pcs 5457, a lot of alarm clocks, radio clocks.. )

author: retiredfeline
author_rank: Frequent Contributor
timestamp: December 21, 2020, 09:26:27 pm
content: Duplex probably refers to a multiplexing technique for reducing pins that I've seen in other clock chips, most recently a current Chinese part, where the half of the LEDs are powered on each half cycle of the rectified but unsmoothed AC supply. So you will need the datasheet anyway for more details.

author: rsjsouza
author_rank: Super Contributor
timestamp: December 21, 2020, 10:51:58 pm
content: For duplex digital LED displays, check the TMS3450 datasheet. it probably follows the same idea (they were competitors at the time).https://www.alldatasheet.com/datasheet-pdf/pdf/86980/TI/TMS3450NL.htmlIf could spare a couple of these and don't mind shipping overseas, I would love to explore them. Let me know.

author: retiredfeline
author_rank: Frequent Contributor
timestamp: December 21, 2020, 11:05:38 pm
content: Quote from: rsjsouza on December 21, 2020, 10:51:58 pmJust be sure to get a 60 Hz one if OP has any otherwise you'll have a clock that runs 20% faster if you intend to put it to use.Decades ago, I was told the story of some workers who "liberated" digital clocks from an assembly factory in SEA. They discovered that they ran at 5/6ths the correct rate as they were intended to be sold in the US.

author: amyk
author_rank: Super Contributor
timestamp: December 22, 2020, 12:01:39 am
content: Quote from: tooki on December 21, 2020, 11:00:30 amThat's not a "databook", it's a "handbook" with only brief descriptions of the parts. Looking in the 1977 MOS LSI databook which has a bunch of clock ICs, there's MM5402 and MM5405, but not 5422, so it was introduced probably '78 or '79.In the 1980 MOS LSI databook, there is the full datasheet for the MM5456 and MM5457 which is here:https://datasheetspdf.com/pdf/506338/NationalSemiconductor/MM5456/1, but nothing for the 5421 or 5422, so it might've been a very short production.Edit: comparing the 5421/22 and 5456/57 general description, it appears the only difference between them is the 2x has "An alarm output is provided that "beeps" a ~15% duty cycle" while the 5x has "An alarm output is provided that "beeps" a50%duty cycle". Everything else is the same, and I bet the pinout is too. I guess the 15% didn't sound as good as the 50%

author: rsjsouza
author_rank: Super Contributor
timestamp: December 22, 2020, 03:00:05 am
content: Quote from: retiredfeline on December 21, 2020, 11:05:38 pmGood call, the MM5422 is only 50Hz. Perhaps that is why the Fairchild 3817A was more popular as it accepted both frequencies - most alarm clocks had a small wire inside that you could cut to convert it to 50Hz if needed.One additional problem is the duplex display - if I understood correctly, the LED segments must be anti-parallel, which would probably require a custom job nowadays (I didn't search, though).

author: Martin.M
author_rank: Frequent Contributor
timestamp: December 22, 2020, 03:00:47 pm
content: found something about 5457 here:https://pdf1.alldatasheet.com/datasheet-pdf/view/113385/NSC/MM5457.htmlit`s useful except the display open question: here is common anodeTMS3450 seems to be common cathode displays.When I find a internal shematic of this displays I can homebrew one for testing, made from little LED :-)

author: retiredfeline
author_rank: Frequent Contributor
timestamp: December 22, 2020, 03:16:55 pm
content: It's really a simple duplexing scheme. Half the segments have a common anode connection and the other half the other common anode connection. So from 12 pins you can get 24 independent segments. 3 digits for M, 10M and H = 21 segments, segment B and C for 10H = 2 segments, and last segment is for PM indicator. Each output pin is labelled with 2 abbreviations. For example: HUB = hour units segment B, MTC = minute tens segment C. You could connect up 24 LEDs and figure out which side of the centre-tap winding will activate which half.The scheme is slightly modified for 24 hour display. In that case there are "segments" HTB, HTC, and HTADEG, so that it can display nothing, a 1 (B+C), or a 2 (B+ADEG). The PM "segment" is then not needed. Clever.Your biggest problem will be getting a suitable display. You could make segments with chained LEDs but that's a lot of soldering.

author: tooki
author_rank: Super Contributor
timestamp: December 22, 2020, 10:50:55 pm
content: Quote from: amyk on December 22, 2020, 12:01:39 amWhy the attitude?!?I described the PDF as "this PDF", without making any claims as to what kind of document it is. The file name clearly says "handbook". And given that it'sliterallythe only document on Google with any information whatsoever about this part, it's better than nothing…Quote from: amyk on December 22, 2020, 12:01:39 amIf it's not in the '77, then it's not "probably" introduced in '78 or '79, butnecessarily, given its presence in the '79 book.