Jellybean logic chips

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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?

Just daydreaming here.

TIA

Re: Jellybean logic chips

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Recent one? Standard TTL is obsolete for years by now and FAIK it is not
produced anywhere anymore.

petrus bitbyter



Re: Jellybean logic chips
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Go over to Digikey.com and enter 74ls into the search box.

Maybe not as many as a few years ago, but still hundreds of parts still
available.

And Digikey only sells what is currently available.

don



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Re: Jellybean logic chips

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LS is not "standard TTL".  ;-)  It's SDTL.  

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I note that they do carry some 74xx stuff but at a buck a pop tells me they're
obsolete.

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Re: Jellybean logic chips

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Standard TTL are the parts numbered SN74xx or some SN74xxx and equivalents.

The parts numbered SN74LSxx are LOW POWER Schottky TTL. Most of them are
still widely available.

petrus bitbyter



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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.


--

John Devereux

Re: Jellybean logic chips
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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
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Re: Jellybean logic chips
On Jan 16, 4:55A0%pm, Phil Hobbs
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As with the 555 - legacy designs and legacy designers, plus the
occasional good fit in an odd situation.

--
Bill Sloman, Nijmegen

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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
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Re: Jellybean logic chips
On Mon, 16 Jan 2012 12:11:39 -0500, Phil Hobbs

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equivalents.
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Why doesn't somebody make the mosfet equivalent of the ULN2003?

John


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   No need for one?


--
You can't have a sense of humor, if you have no sense.

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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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Re: Jellybean logic chips

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   Still no need, if you can find better students. :)

--
You can't have a sense of humor, if you have no sense.

Re: Jellybean logic chips
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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.

Re: Jellybean logic chips
On Jan 16, 6:11A0%pm, Phil Hobbs
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"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
designsA0%and 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.

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The 7406 was handy, but it's been a very long time since I designed it
into anything.

--
Bill Sloman, Nijmegen

Re: Jellybean logic chips
On Mon, 16 Jan 2012 15:39:08 -0800 (PST), Bill Sloman

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I
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not
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equivalents.
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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.


Re: Jellybean logic chips
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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.

--
Bill Sloman, Nijmegen

Re: Jellybean logic chips
On Mon, 16 Jan 2012 12:21:02 +0100, "petrus bitbyter"


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And if you are pretty desperate for replacements, look for SN54xx with
extended temperature range.


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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...



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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.
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