Solved: Can SN74HC595N replace TC74HC595AP?

Go To Last Post
19 posts / 0 new
Author
Message
#1
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi, 

I find it dificult to find the TC74HC595AP. 

Can I use SN74HC595N instead? 

Similar enough? 

 

I fear they are not similar enough since the circuitboard includes both.

Why should it have two "different" if they had the same function?

I just can't se any major difference. Pinning seems the same, and timing seems the same as well from what I can see. 

 

Datasheet for TC74HC595AP:  https://pdf1.alldatasheet.com/datasheet-pdf/view/31763/TOSHIBA/TC74HC595AP.html

Datasheet for SN74HC595N:  http://www.ti.com/lit/ds/symlink/sn74hc595.pdf 

 

Thanks in advance! 

Last Edited: Sun. Jun 16, 2019 - 12:43 PM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

On the surface they should be interchangeable. Why the different prefix and suffix? Different manufacturers.
What is this ‘circuitboard’ you speak of? Otherwise are you expecting us to findthe difference in some obscure specification?

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Shouldn't this be in General Electronics? * Your wish is ... *

 

Back when I was your age, the IC Master book and similar sources had such cross-reference information.  In addition, manufacturer's would have replacement lists.

 

Oh, wait -- a Google search uncovers similar online sources today.

 

As hinted, what do the given suffixes represent for variant?

 

What application has great importance on the variations in the common '595?  Clocking so fast that specs might be violated?  With an AVR?!?

 

 

You can put lipstick on a pig, but it is still a pig.

I've never met a pig I didn't like, as long as you have some salt and pepper.

Last Edited: Sun. Apr 7, 2019 - 02:03 PM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

I fear they are not similar enough since the circuitboard includes both.

Did you consider the case that they purchased both kinds since either was acceptable? 

 

What circuit board?  Why do you care what they used?

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi, 

Thanks for you replies. 

avrcandies: Yes, thought about it. 

 

Kartman and avrcandies: The circuitboard is a panel with a lot of buttons controlling different relays. 

 

If there is important differences, it should be described in the official "obscure specification", if not, how should anyone know if the part is what they need? 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

The 74Hc595 is a generic part number. This part is made by a number of manufacturers and they are all similar, but not identical. The difference could be one parameter out of 100’s. Without any context given by you, how would we be able to make a determination? For example - the toshiba part might be able to be clocked 5MHz faster than the TI part. Your circuit might exploit this, so using a TI part would probably not work. Or vice versa. So, assuming your circuit doesn’t require anything special, both parts are functionally identical.
I had an instance where a contract manufacturer used counterfeit chips in one of my designs. The counterfeit chip was functionally identical but electrically sonewhat different. My design relied on a number of specs of the chip i chose and failed with the counterfeit parts. I suspected the supplier laser etched some similar, but cheaper parts.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 1

If the circuit board includes both and you need a electronics engineering degree to tell the difference, then most likely they are identical in use on the PCB.  The manufacturer's parts department bought received different batches for what is essentially the same part and are simply mixing them all together during assembly.  Occam's razor.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

You need to be VERY careful not to assume that, because there is some small difference between A & B, that the difference is significant.

 

Lets take a simple example. Suppose that A is rated for operation from -10C to 80C and that B is rated for operation from -25C to 90C. Now, lets further assume that they are located on the same circuit board. So, just because the two are rated at different temperatures, does that imply that you need to purchase two different ones?

 

I would argue - very likely not. What could lead to one being exposed to significantly higher or lower temperatures than the other? They are close to each other on the same board. Temperature difference won't likely occur due to external circumstances. Does one have higher internal power dissipation that could lead to the need for a higher temperature rating? Thats possible, depending on the load that each device drives. But, a logic device, an 8-bit latch and shift register? Pretty unlikely.

 

Thus, you need to look at more than the gross numeric differences between the two. You also need to consider whether the detected differences are significant IN THE CONTEXT OF THE APPLICATION. Thus, if YOU do not understand what those spec sheets mean, or how the device operates, find someone who can help you. You could be safe assuming that the two devices are replacements for each other, or maybe not. 

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0


 

Few years ago I was designing a CNC panel that required several 7 Segments LED displays, LEDs and switches.

I tried several schematics using HC595, even built a complex prototype, worked okay, but too much discrete transistors and resistors for the multiplex driver.

At that time I fould the (TI)  TPIC6C595 , it is DMOS transistors open collector at the output, can only drain current (requires Common Anode displays, or low drive anything else), but can deal with 33V feeding the loads, and can drain more than 100mA per output pin.

It was very interesting, but then I also found the MAX7219 in PDIP e SOIC package, and also ready assembled with 7Seg LED displays, at AliExpress... much easier to control, reducing a lot the software.  The only issue with the MAX7219 is that it uses COMMON CATODE 7seg displays, what is a little odd for me - I had hundreds of Common Anode units around, but no problem, Common Catode still very cheap, even the half inch size, and now they have all sort of colors, even white and blue... wow.

 

The MAX7219 is cascaded possible, so you can connect several boards in series, and send a long train of bits for all of them in high speed via the same AVR SPI port pin (DIN CS and CLK), the ready made 8 digits little board made in China has only 5 pins, VCC, GND, DIN, CS, CLK and cost US$2.27 free shipping.  Once you sent the data, the MAX7219 takes care of the multiplexing, programmed intensity, etc, your AVR will be free to do other things, and for that price, impossible to beat with HC595 and displays.  I know, you will be driving relays, but I could not refrain myself to post this.

 

 

Today the Chinese market is pushing strongly the TM1637 chip with displays, price is even lower. You can buy a ready made 4 7seg digit display with the chip for less than US$0.70 and free shipping (that is magic price, right?), but TM1637 uses I2C communication protocol, if you will write assembly it complicate a little bit further than the MAX7219.  Of course, market is pushing this chip for the Arduino, TM1637 I2C libraries are ready made and user don't even know what is happening, it works.   Apart of this, I wonder why the Chinese still referring to 7seg LED display as Digital-Tube... and "high intensity" as "high pressure".  Translation really sucks laugh

 

 

 

Wagner Lipnharski
Orlando Florida USA

Last Edited: Mon. Apr 8, 2019 - 12:59 AM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

There's no substitute for understanding your circuit (or the circuit you are repairing) & what is obscure or critical.  Sometimes parts are spec'd by price.

For example, one board I have created, needs a cap with maybe a 20% tolerance.  But I can actually get a particular 10% part cheaper at digikey, so its on the BOM.  Someone comes along 1 year later & says those parts are on backorder, so we must get a replacement 10% or 5% cap, which costs $$$, when they could have gotten a 20% part.   The BOM simply doesn't provide enough info.

 

Some circuit portions may require very exacting specifications be met, other portions may be happy as long as the part can be spelled N-P-N.   

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

So did you state the minimum tolerance in your build documentation? Just asking... cheeky

Ross McKenzie ValuSoft Melbourne Australia

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

 

So did you state the minimum tolerance in your build documentation? Just asking.

It might be in some technical documentation, but that generally does not cover every component, by component.   Purchasing usually only has a BOM in a computer, let alone a schematic. 

Once a part number is recorded, it takes on its own life, defining the future. 

Occasionally someone will question something...why do we need wire rated to 150C? ...hmm nobody knows...been using it last 10 years, per the BOM.....turns out that's what they had a ton of it gathering dust in inventory when the product was designed.   But 105C wire would be fine.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0


 

Big thanks to all of you for great replies, stories and examples! 

It is a pretty simple board with buttons and lights as said. Some activates a relay while holding the buttons, other buttons activates the relay by a single push, and turns of with a single push. 

So the details in the spec probably isn't too important, but as k7ehk wrote, it's important to be careful. 

I think someone has already changed the ones that are Texas Inst. because I've got a working card, and that one has Toshiba-chips only. 

Maybe the ones from TI isn't similar enough, because the problem with the card is that it enters alarm-mode when powered, and I can't controll the buttons. 

Just don't know if the problem was the same before they were changed. I'll try to find out. 

 

Btw. anyone that has seen this kind of buttons, and know where to find them? No markings on them. The surface above them can only be pushed maybe 1mm, so I don't have too many replacement-options that will work. 

 

 

Reduced image size- JS

 

Attachment(s): 

Last Edited: Wed. Apr 10, 2019 - 12:54 AM
  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Well, you can't be too careful, but generally digital ICs with the same generic part number have the same specs. The extra letters/numbers  spec things like package type and temperature range. So, if the manufacturer's part number is for the same options, you should be OK - as long as you stick with major vendors. 

 

Years ago, companies like CDC and another defunct computer firm(that I was at briefly) created their own data sheets for situations like this. They had all of the specs and incoming inspection could test parts from various vendors to see if they met the generic spec. I think that the big boys still do this. Designers choose standard parts from the company part numbers and purchasing can look for the best deals from qualified vendors. Critical parts are critical parts and they need to be spec'd as such. Unless a particular vendor specs different tolerances from the other companies , there's no guarantee that they will always produce better results. Note, if a vendor can make better parts than others, they will probably brag about it.

 

I did not check all of the spec sheet data, but I did do a quick look at Mouser. The Toshiba part is listed as obsolete, so they probably aren't making them any more. Unless there is some spec difference, the TI parts should be fine. If they are not, then  not all Toshiba parts will work either. I would suggest a careful comparison of the spec sheets. Mouser has links to the official spec sheets for all of  their parts ( as does Digikey et al). Make sure that all of the options are the same and see what you find. I doubt that the vendpr is critical.

 

Good Luck,

 

hj

 

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

The 595’s control the leds, the 165’s read the pushbuttons.

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

For general reference, and a slight correction to Ford2go's post: logic parts with the same generic part number generally have the same *digital* function.

 

However - and this has bitten me recently - different manufacturers and in particular different families *will* have differences, some significant, some not so.

 

For example, a 74hctxx will almost always work where a 74hcxx works - but the trigger voltages for the hc part are different from those of the hct, as are the output levels. hc works usually from 2 to 6v, but *some* hct, depending on manufacturer, will work at 6v, with a maximum Vcc of 7v even though hct spec is 4.75 to 5.25v vcc. At 3v3, most hct will still work quite happily except for strange logic levels, and the unexpected fact that the propagation delay increases. Which is usually fine, until you're trying to make a 32MHz oscillator with an inverter stage with a 50ns propagation... you will scratch your head on that one!

 

The only answer here is to read the datasheets, particularly those handy tables, very carefully... and when you find a difference, check very carefully to discover if it makes a difference to your circuit.

 

Neil

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

"T" stands for TTL compatibility....HCT was introduces around 1984, since standard high speed cmos (HC) was not very compatible with the widely used TTL chips , at the time.  I remember the cheer in the lab when we heard of the parts.

 

 

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Not that in the OP's application will this make a difference, but a cursory read of the datasheet shows the following difference:

 

 

 

Not going to dig deeper.

 

Right Side JIm

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

  • 1
  • 2
  • 3
  • 4
  • 5
Total votes: 0

Hi, 

Just wanted to say thank you for your help! 

I found a place that had some old Toshiba-cips left, and was able to order a few. 

After replacing the TI-chips with the Toshiba-chips, the alarm was gone, and after repairing a broken path as well, the board worked perfectly! 

For the other board with non-working LEDs, I replaced two of the chips there as well, and now that board works too, so now I have two perfectly working boards! 

 

About the buttons, two of them wasn't in use, so I used them to replace two of the bad ones, and the two remaining that was working only with a hard push, I placed them at rarely used locations. 

 

Thanks again!