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Whats the deal with chips that have the same data sheet and different postfixes? — Parallax Forums

Whats the deal with chips that have the same data sheet and different postfixes?

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2012-10-20 20:15 in General Discussion
Ok so I was looking around and stumbled across the TLC5940 which is a chip TI markets twords LED applications it can generate 16 PWM lines, I thought wow this is cool maybe I can run this into an h-bridge and use it for motor control, and had looked up some people doing this with an arduino. Im thinking a few different H-bridges with these chips, current sensors, and an arduino chip would be an awesome way to make a motor controller board that could handel DC motors with feed back, servos and steppers, that way you can offload all the motor control from your propeller or even bs2!! Sure theres alraeady awesome systems like the HB-25 but those cost money.

Anyways to the point im looking at the TI sample page and this happens alot there are two different versions of this chip the TLC5940NT and tlc5940NTG4.

http://www.ti.com/product/tlc5940

Anyways as far as I can tell most of the time these chips are the excact same, they usually have the same data sheet etc, so whats the difference when you see chips like this with different part numbers in the same package with the same data sheet?

Comments

  • Mark_TMark_T Posts: 1,981
    edited 2012-10-20 18:01
    It depends - its up to the manufacturer really. Clearly different packaging is indicated by suffixes, but sometimes more radical differences (just been looking at CAT4101 variants, some have 4 LED outputs, some 1 LED output)

    I think the main point is that when there is a close family relation there is no sense to having separate datasheets - for instance single v. dual v. quad opamp (though for opamps the difference is usually in the part number as it happens) When the relationship is close enough there is no point having separate part numbers because the part number really serves as a name for the basic function (for instance Z80-A, Z80-B microprocessors, various 555's) - so its partly marketing (the part number as brand?)
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2012-10-20 18:11
    I think the G4 suffix had to do with the transition to RoHS and green status. For a while, old stock was available that did not meet the requirements or was in a transitional state. TI came up with a confusing array of suffixes to account for that. You can read in the data sheet that both of those part numbers meet the standards. It may be that at some point they will phase out the special suffix. There may be a little more to it than that, but electrically I'm sure you are on safe ground with either part number.
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-10-20 18:28
    Just like Tracy said:

    My guess is the part was always RoHS compatible. Just wasn't certified that way.
    The new part is the same as the old part just labeled properly now with the proper paperwork.

    I've seen this before.

    Duane J
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-20 19:22
    A lot of times, different suffices are used to differentiate between different temperature ranges (e.g. industrial vs. commercial), different supply voltages, or different clock speeds. You really need to consult the datasheet, because there is no single rule for assigning a part number suffix. Case in point: the L393 series bridge drivers.

    -Phil
  • Duane C. JohnsonDuane C. Johnson Posts: 955
    edited 2012-10-20 19:26
    However, I can't see the difference between the two suffixes on that data sheet.

    Duane J
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-10-20 19:49
    Im pretty sure Duane is right, thats why I asked this question. The last time it came up was the l293d vs the l293de4 from TI, there is no difference in tempature, ROHS compliability voltage anything, its like the same exact chip all over. Many times the answer is obvious just by browsing the specs like Phil said its either voltage or commercial vs industrial tempature. For instance when looking at Maxim or Microchip products the suffix is immediately obvious as package/temp/voltage or just a genral upgrade, but at TI and a few other suppliers Ive sat for an hour before ordering trying to find the difference with no apparent conclusion. I guess the question I should have asked is Why does TI/National have different part numbers for the same part
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-10-20 19:51
    In the case of the TLC5940NT vs. 'NTG4, Tracy is spot on. According to the TI website, the G4 suffix was added to designate, at the time, newly-available RoHS parts, so that customers would not have to refer to the datecode to determine RoHS compliance. However, newly-minted 'NT parts are also RoHS compatible, but earlier datecodes will not be. When purchasing new parts the two will be identical. But, if you buy surplus or old stock, the 'NT suffix will not be a reliable indicator of RoHS compliance without also referring to the datecode.

    BTW, DigiKey lists both parts as being RoHS-compliant. So, it's clear that they have nothing but fresh stock in their inventory.

    -Phil
  • YanomaniYanomani Posts: 1,524
    edited 2012-10-20 20:09
    Hi Duane.

    Looking at http://www.ti.com/product/tlc5940#topsidemarking tells me that there is no diference at the top side marking of the devices.

    Digikey's http://www.digikey.com/scripts/dksearch/dksus.dll?AlternatePackaging&name=TLC5940NTG4-ND adds a bit to the team riot too (no connection with USSR punk women band, please ;).
    Looking at that page made me think that it's only a matter of minimum order quantity to get them sent directly from TI's factory. A lovely discount by agreeing to buy 195 moq but, even there, no diference at all.

    The doubt persists.

    Yanomani
  • YanomaniYanomani Posts: 1,524
    edited 2012-10-20 20:15
    Hi Phil. In the mean time I was typing my former post (english is not my mother tong, so it takes me some time to do it) and when the page refreshes there is yours and you hit the point.

    Thanks for the clarification.

    Yanomani
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