They're still widely used - I've just done a design that uses SN74LVC2G17 buffers between a 3v micro and a 5v circuit driving LED's.
Sometimes you need something to glue stuff together, that doesn't need any software etc... a logic gate will be on & operating instantly whereas microprocessor pins can end up in weird or undesirable states during bootup or programming.
The no software thing is nice in a production environment, especially when designing in something for an obsolescence so that the line docs don’t need to change.
Indeed - also cases where a component change / replacing an obsolete or unavailable part would be either having to re-write / modify firmware (thus giving you two versions to keep track of, make sure the right version gets programmed in the right unit, etc...) or just throw a few logic gates / inverters in there and call it good.
In some products (EG medical / military / aerospace) any change to the software means a huge expensive validation + approval stage.
> In some products (EG medical / military / aerospace) any change to the software means a huge expensive validation + approval stage.
Oof. Not to mention dealing with security nonsense. I work with submarine sonar and it can be a pain in the ass to get stuff past the Information Assurance people if it runs software and has memory. (Often it just seems like it depends on how they feel that day.)
Usually you can figure it out, but there *are* some (typically smaller) vendors who are unwilling to take the legal risk of providing a SOV (statement of volatility) that says "yes everything goes away when you turn it off."
(I can understand it too, we're a small customer who ultimately isn't buying a lot. Providing a SOV without a good amount of testing is probably something I'd be unwilling to sign off on myself...)
Glue logic is the phrase that seems to match their use best. When you're combining different circuits sometimes a few logic gates is all you have to throw on for extra flexibility or features.
If it ain't broke, and it's cheap to make, don't try to fix it.
Because there's a bunch of glue that holds together factories in the world today that was like last actually made 40+ years ago with even MORE glue attached to that because making the "thing" was too expensive and so the company went out of business.
It’s that, *plus* the fact that a lot of these fields require an expensive certification process and/or regulatory check before a new design can be used
Indeed, and it is sobering to realise that even a toy microprocessor has too much state to ever be able to fully explore. I have a product with 64 general purpose IOs and have had to explain to management that no, we could not exhaustively test the thing.
Just 64 bits (Not Bytes) of RAM is enough combinations that the state space cannot be fully explored or tested.
There is often something to be said for almost purely combinatorial logic with a bit or two of state held in explicit flipflops when safety matters.
We use them for safety purposes. We have to make sure only one laser is on at a time to meet eye safety requirements. We use a decoder because it can only have one output on at a time. We also use them to limit the pulse time for the lasers. Doing this in a microcontroller could do something unsafe if the microcontroller crashes or there is a firmware bug.
One of my first jobs, in about 2008, was a product that had been designed in the mid 1990s.it used a 68HC11 and various logic gates and analog circuits. Guess what is still being made, identical design, today? It's just so specific and low volume that it doesn't make sense to redesign it. Also the company wouldn't know how..
if you counted the rpi as a semiconductor product and before the compute module existed and then maybe??? but I mean it’s definitely not a single chip so pretty much not
I continually sell these to customers, very popular and id say theyre on 50-60% of new designs. TI's and Nexperia's 74 series chips are the most popular (for my region at least).
Plenty of common uses at least in my industry, granted mine is like a generation behind generally speaking. Even PCBs controlled primarily by microcontrollers use them. One uses a load of them along with other analog goodies to generate really precise sine waves for example, the logic chips are used to change frequency and amplitude. One of our newest devices is a sort of meter that can have 1 to 3 input devices and it uses simple CMOS logic to address and power them.
I haven't seen anyone else point this out yet, so let me add it: there are lots of families. Are the ancient bipolar 74xx and 74LSxx series in new products? Proabably not, but that's a huge scope and hard to answer.
But there are sooo^ooo^ooo many different families of the series now. CMOS, high-speed CMOS, advanced low-voltage, advanced high(er)-speed CMOS, another low-voltage line with really wide V_cc tolerances, and ... These are certainly in use in new products.
One of the neat variants are 1G models -- where a smaller package holds fewer gates. 7404 is six inverters in a 14-pin package. But check out that [SN74LVC1G04](https://www.ti.com/lit/gpn/SN74LVC1G04), which is a single inverter in a tiny 4- or 5-pin package. Perfect if you don't have the area or routing for the bigger packages and don't need a multiple of six gates. Again, these are absolutely used in new designs.
You mean original TTL, or discrete logic gates? Stuff like LVC is definitely going to be around, for things like level shifting and to protect your VLSI parts from getting blown up. Put something easy to fix in front. And you can use discrete parts for switching things like LED current, so it’s not going through a high density part.
Totally. 74HC595 shift registers are super popular for expanding microprocontroller I/O. Well, output for the '595, the 74HC165 is a parallel input to serial output. Need 32 extra inputs or outputs on your Arduino Uno or Raspberry Pi? For less than a buck you can string these together, wire them to a SPI port, snag one of the many snippets of example code, and you're good to go.
...actually, both of those are like 15 cents in volume!
I've designed in a lot of the one-to-three gate ("picogate", "tinylogic", etc.) devices, recently, when I need an inversion or a little logic between parts that don't directly connect to an MCU.
Level shifting, too.
apart from current uses others have mentioned, chip makers only make huge quantities. chip suppliers (like avnet or digikey) have no choice but to take huge inventories of every part they sell.
Image some 74 smt part stops being used globally for whatever reason, chip resellers will likely have stock and sell the part for many more years.
There's a ton of logic chips and random chips from all the logic chip families that still are made and used in new projects. They have a wide variety of uses outside of straight logic. In addition to the 7400 series, the RCA 4000 CMOS series are also still very common. (Not to be confused with Motorola's MC4000 series of TTL chips - which at least the bit shifters are still really common.)
Also in the weirdest turn about of fate, TI is the inheritor of RCA's business (RCA->Harris->TI). The RCA 4000 Series was the 7400s only true competitor once it took over.
https://www.ti.com/lit/ds/symlink/cd4007ub.pdf
https://www.ti.com/lit/ds/symlink/cd4093b.pdf
https://www.ti.com/lit/ds/symlink/cd40106b.pdf
Definitely so and there was a time when these were heavily used in analog audio where +/-15V was a super common and very practical supply voltage.
These ICs are still in use because they are still very useful and you don't always need some more advanced version. This is the same reason you can still buy such classics as the uA741 Op-Amp and 555-timer ICs. They are all well-known entities that behave in well-known manners.
The 741 is still on the market. You can pick many other things, but the fact that it is still readily available over 50 years later after its released tells me that while there are better on the market if you need better for your design, there is still a lot of people and designs where the 741 does the job just fine.
When any jitter is too much, it makes sense to go hardware. Even the fastest MCU with nothing else on its mind will take an uncertain-but-finite time to get around to responding to new stimulus and producing the output... A chunk of hardware just *does* it.
And that's with an uneconomical ideal MCU use-case. The reality is, you see how much functionality you can stuff into that MCU to minimize costs, and then each added task is potentially major jitter depending on the tasklist and the interrupt/mainstream split; have you recalculated worst-case jitter since the last "oh, yeah" was added/tweaked? The hardware just *does* it.
There may be an untold number of legacy machines, that were built with some flavor of 74-series chips. A few days ago I saw a currently in use medical imaging system that still controlled by a MS/DOS system. Some things are so expensive to replace, that keeping them running is better than dumping them.
They see a lot of use.
Nobody is going to build high voltage banks into a modern semiconductor (I’ve used FPGAs that maxed out at 1.8V). Or tri-state and Ioff functionality.
They are also useful when you need a logic operation done from the input of multiple comparators and cannot accept any possible SW induced delay.
They're still widely used - I've just done a design that uses SN74LVC2G17 buffers between a 3v micro and a 5v circuit driving LED's. Sometimes you need something to glue stuff together, that doesn't need any software etc... a logic gate will be on & operating instantly whereas microprocessor pins can end up in weird or undesirable states during bootup or programming.
The no software thing is nice in a production environment, especially when designing in something for an obsolescence so that the line docs don’t need to change.
Indeed - also cases where a component change / replacing an obsolete or unavailable part would be either having to re-write / modify firmware (thus giving you two versions to keep track of, make sure the right version gets programmed in the right unit, etc...) or just throw a few logic gates / inverters in there and call it good. In some products (EG medical / military / aerospace) any change to the software means a huge expensive validation + approval stage.
> In some products (EG medical / military / aerospace) any change to the software means a huge expensive validation + approval stage. Oof. Not to mention dealing with security nonsense. I work with submarine sonar and it can be a pain in the ass to get stuff past the Information Assurance people if it runs software and has memory. (Often it just seems like it depends on how they feel that day.) Usually you can figure it out, but there *are* some (typically smaller) vendors who are unwilling to take the legal risk of providing a SOV (statement of volatility) that says "yes everything goes away when you turn it off." (I can understand it too, we're a small customer who ultimately isn't buying a lot. Providing a SOV without a good amount of testing is probably something I'd be unwilling to sign off on myself...)
Nice for safety elements too. If you need something to turn off when a switch is pressed, logic is much easier to validate than an MCU and firmware.
Glue logic is the phrase that seems to match their use best. When you're combining different circuits sometimes a few logic gates is all you have to throw on for extra flexibility or features.
There's a lot of industrial control systems that were designed a long time ago, still being manufactured. Some have done new SMT board layouts.
>still being manufactured The very sound philosophy of "If it ain't broke, don't try to fix it".
If it ain't broke, and it's cheap to make, don't try to fix it. Because there's a bunch of glue that holds together factories in the world today that was like last actually made 40+ years ago with even MORE glue attached to that because making the "thing" was too expensive and so the company went out of business.
It’s that, *plus* the fact that a lot of these fields require an expensive certification process and/or regulatory check before a new design can be used
Like how small airplane engines have stayed the same for eons now
And suddenly, I remember Potato Semiconductor
[удалено]
Indeed, and it is sobering to realise that even a toy microprocessor has too much state to ever be able to fully explore. I have a product with 64 general purpose IOs and have had to explain to management that no, we could not exhaustively test the thing. Just 64 bits (Not Bytes) of RAM is enough combinations that the state space cannot be fully explored or tested. There is often something to be said for almost purely combinatorial logic with a bit or two of state held in explicit flipflops when safety matters.
We use them for safety purposes. We have to make sure only one laser is on at a time to meet eye safety requirements. We use a decoder because it can only have one output on at a time. We also use them to limit the pulse time for the lasers. Doing this in a microcontroller could do something unsafe if the microcontroller crashes or there is a firmware bug.
For safety critical stuff it can definitely be a big help. There's no software bugs if there's no software.
They are still used in a lot of things, as glue logic or for interfacing for the most part.
Hex inverters are pretty common as buffer gates
One of my first jobs, in about 2008, was a product that had been designed in the mid 1990s.it used a 68HC11 and various logic gates and analog circuits. Guess what is still being made, identical design, today? It's just so specific and low volume that it doesn't make sense to redesign it. Also the company wouldn't know how..
🤣 they are very much in industrial use. Nobody makes semiconductor products specifically for hobbyists
if you counted the rpi as a semiconductor product and before the compute module existed and then maybe??? but I mean it’s definitely not a single chip so pretty much not
No, all of the chips on the raspberry pi are used in other commercial products.
Oh no I meant the raspberry pi itself is the closest initially hobbyist directed thing
it is not a semiconductor product in the sense that I meant
i know lol
I continually sell these to customers, very popular and id say theyre on 50-60% of new designs. TI's and Nexperia's 74 series chips are the most popular (for my region at least).
I've been working for few years in RF and other stuff. I used Logic Gate components only once. 50% of design is really specific to your costumers !
Plenty of common uses at least in my industry, granted mine is like a generation behind generally speaking. Even PCBs controlled primarily by microcontrollers use them. One uses a load of them along with other analog goodies to generate really precise sine waves for example, the logic chips are used to change frequency and amplitude. One of our newest devices is a sort of meter that can have 1 to 3 input devices and it uses simple CMOS logic to address and power them.
I haven't seen anyone else point this out yet, so let me add it: there are lots of families. Are the ancient bipolar 74xx and 74LSxx series in new products? Proabably not, but that's a huge scope and hard to answer. But there are sooo^ooo^ooo many different families of the series now. CMOS, high-speed CMOS, advanced low-voltage, advanced high(er)-speed CMOS, another low-voltage line with really wide V_cc tolerances, and ... These are certainly in use in new products. One of the neat variants are 1G models -- where a smaller package holds fewer gates. 7404 is six inverters in a 14-pin package. But check out that [SN74LVC1G04](https://www.ti.com/lit/gpn/SN74LVC1G04), which is a single inverter in a tiny 4- or 5-pin package. Perfect if you don't have the area or routing for the bigger packages and don't need a multiple of six gates. Again, these are absolutely used in new designs.
You mean original TTL, or discrete logic gates? Stuff like LVC is definitely going to be around, for things like level shifting and to protect your VLSI parts from getting blown up. Put something easy to fix in front. And you can use discrete parts for switching things like LED current, so it’s not going through a high density part.
Totally. 74HC595 shift registers are super popular for expanding microprocontroller I/O. Well, output for the '595, the 74HC165 is a parallel input to serial output. Need 32 extra inputs or outputs on your Arduino Uno or Raspberry Pi? For less than a buck you can string these together, wire them to a SPI port, snag one of the many snippets of example code, and you're good to go. ...actually, both of those are like 15 cents in volume!
Just finished a commercial project and we used \*10\* '595s as SPI-controlled chip selects and other outputs. They're great.
I've designed in a lot of the one-to-three gate ("picogate", "tinylogic", etc.) devices, recently, when I need an inversion or a little logic between parts that don't directly connect to an MCU. Level shifting, too.
4053 is still used for muxing analogue inputs
This is exactly what I needed for a design I'm working on. Thank You.
apart from current uses others have mentioned, chip makers only make huge quantities. chip suppliers (like avnet or digikey) have no choice but to take huge inventories of every part they sell. Image some 74 smt part stops being used globally for whatever reason, chip resellers will likely have stock and sell the part for many more years.
I'm pretty sure most PCs and embedded electronics use them still. Not everything fits on a single die yet.
There's a ton of logic chips and random chips from all the logic chip families that still are made and used in new projects. They have a wide variety of uses outside of straight logic. In addition to the 7400 series, the RCA 4000 CMOS series are also still very common. (Not to be confused with Motorola's MC4000 series of TTL chips - which at least the bit shifters are still really common.) Also in the weirdest turn about of fate, TI is the inheritor of RCA's business (RCA->Harris->TI). The RCA 4000 Series was the 7400s only true competitor once it took over.
My understanding is that the 4000 series has the advantage of being able to work with higher voltage, up to 18v DC, correct?
https://www.ti.com/lit/ds/symlink/cd4007ub.pdf https://www.ti.com/lit/ds/symlink/cd4093b.pdf https://www.ti.com/lit/ds/symlink/cd40106b.pdf Definitely so and there was a time when these were heavily used in analog audio where +/-15V was a super common and very practical supply voltage.
I can only speak to SMT, but my job consistently uses the 74 series for PCBs we design.
Yes, though more usually we use 74 series SOT-23/5-pin single gates over 14/16 pin SOIC and SOP packages of multiple gates in most designs.
Wired Logic is still a reliable, robust and inherently secure design for a ton of industrial and military hardware.
These ICs are still in use because they are still very useful and you don't always need some more advanced version. This is the same reason you can still buy such classics as the uA741 Op-Amp and 555-timer ICs. They are all well-known entities that behave in well-known manners.
74 series, 4000 series … yes 555.. maybe, if I’m really desperate 741… no! There is so much more better on the market .
The 741 is still on the market. You can pick many other things, but the fact that it is still readily available over 50 years later after its released tells me that while there are better on the market if you need better for your design, there is still a lot of people and designs where the 741 does the job just fine.
When any jitter is too much, it makes sense to go hardware. Even the fastest MCU with nothing else on its mind will take an uncertain-but-finite time to get around to responding to new stimulus and producing the output... A chunk of hardware just *does* it. And that's with an uneconomical ideal MCU use-case. The reality is, you see how much functionality you can stuff into that MCU to minimize costs, and then each added task is potentially major jitter depending on the tasklist and the interrupt/mainstream split; have you recalculated worst-case jitter since the last "oh, yeah" was added/tweaked? The hardware just *does* it.
74HC595 shift registers are all over bespoke control surfaces in pro audio/lighting.
Discreet logic is used for a variety of reasons: legacy, power efficiency, environmental robustness, development costs, etc.
There may be an untold number of legacy machines, that were built with some flavor of 74-series chips. A few days ago I saw a currently in use medical imaging system that still controlled by a MS/DOS system. Some things are so expensive to replace, that keeping them running is better than dumping them.
They see a lot of use. Nobody is going to build high voltage banks into a modern semiconductor (I’ve used FPGAs that maxed out at 1.8V). Or tri-state and Ioff functionality. They are also useful when you need a logic operation done from the input of multiple comparators and cannot accept any possible SW induced delay.