Hi all, (happy new year BTW) How are 74xx chips made these days? Just the same old masks as 30 years ago, or are they die-shrunk along with everything else? I doubt manufacturers keep vintage equipment going just to make old ICs, and I also don't think the die is the same size.
If I crack open a 30 year old 7400 and a recent one, will the die be the same size?
What are the chances that modern 74xx devices are actually a single CPLD that's programmed at the factory to act like a 7400 or 7406?
Of course these days the "jellybean" equivalent parts tend to be low voltage types like 74LV14 or 74LVC14 (with about 20 different families to choose from...).
And 74HC and HCT are still very popular and useful.
And no, none of them are based on CPLDs!
Having said that there are some "configurable" single gate parts that change gate function depending on some pin selections. Never had a use for one of those.
There are still some more specialized original TTL parts, especially the ones with higher drive, e.g. the SN7406 OC inverter/driver. There was a time back in the 80s when it still made sense to use old TTL for that sort of job, because the LS ones were too wimpy. I suspect that it's mostly repair and maybe residual production of those sorts of gizmos that keeps old TTL going.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
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I usually associate the word "legacy" with good things, such as a long-lost uncle leaving me lots of money.
If one happens to need a moderately quick (20 ns) part that will drive six 30V, 40 mA loads, one could do a lot worse than a thirty-cent 7406. Other driver parts such as a ULN2003 Darlington are about the same price, and much much slower, though of course relays and solenoids don't care. (Of course if the pick-and-place costs are low enough, six
2N7002s could be better and cheaper than either.)
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
There's tons-o 74YYxx parts, with YY in {HC, AHC, ALS, VLS, ...}. But straight 74xx parts are rare.
Most of the LSI parts are unavailable -- if you need adders and ALU's and stuff then you're going to want an FPGA or a PAL, so you won't buy 74xx logic anyway. But most of the real jelly-bean functions (gates, some counters, multivibrators, PLL chips) seem to be going strong.
I suspect that they're all new, or perhaps 10 year old technology that's been moved to China and made without care or concern for the factory workers or the factory environs.
--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?
Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com
If you're in the military market, you can get obsolete dies and get your own chips made.... Typical costs per chip..$100x1000pcs But you get to repair that $xMillion piece of 70's state of the art kit...that would cost $100 Mill to replace...
"Legacy" designs are circuits that were designed a long time ago, and still work well enough that nobody is going to pay to update the design for more modern parts. "Legacy designers" recycle old designs=A0and old parts, because they know they work, and the product isn't going to sell in the kind of volume where the money you could save by designing in new parts would to cover the extra cost of working out a new design and getting the bugs out of it, or because they are lazy.
The 7406 was handy, but it's been a very long time since I designed it into anything.
In the industrial automation sector, you are typically required (by contract) to supply spare parts for at least a decade. In practice, in order to keep the customer (for new orders), you have to support systems two or three decades old.
When old components are no longer available, you have to design new boards with current components so that a board or box level replacement can be done.
Been there, done that, but for more recherche part than 74-series logic (where you can usually swap in something more modern without changing board or box). Components like the 555 and 74-series TTL were designed into so many products from 1970 to 1980 that there's still a steady market for them - Farnell still stocks a 7410, a 7432 and a
7447 (and a huge range of 555s), and while specialised suppliers carry more.
Allegro did make a replacement with a single bipolar output stage for improved efficiency.
We just sold out of these.
They were a great student proof I/O.
--
Many thanks,
Don Lancaster voice phone: (928)428-4073
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Blowing things up _occasionally_ is part of learning. Doing it very often is indicative of someone who does not, can not or will not learn and should be placed elsewhere.
The old LabVolt equipment-the OLD, green, LV equipment-had the advantage that it was moderately rugged but would fail if you did something really dumb. BUT it was easily repairable in most cases, by the instructors. You had to have the right tool to open it up. That showed who did what.
Then LabVolt went modern, plus, the big equipment vendors started giving away to schools some of the lab grade stuff-trade-ins, prototypes, loaners, samples- they had been dumpstering to keep off the market. It's hard to justify buying $400 service grade RF generators, for example, when they will GIVE you an HP 8640B or three.
Of course the kids blew up the HP in short order. The school had to have it fixed...
Service grade electronic test equipment may not have any cash value but it can be fixed easily and cheaply. And it works fine for a lot of educational purposes.
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