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SN74LVC1G14: Advice to pick right logic family and devices for next 10-20yrs

Frank Rothoff
Expert 6040 points
Part Number: SN74LVC1G14

My customer question below, I'd appreciate your advice.

currently I’m looking for some Logic IC’s. I want to establish a stable basis for our new device, which should be available for the next 10-20yrs.

Therefor I’d like to use 2nd and 3rd source options, too. Of course TI is my first option.

 

In the first step I took your logic guide and just start with picking LVC series. But for now it is very hard to find other manufacturers.

Maybe you could help me to find a series which is future stable and best for our system.

 

What do we need?

  1. 1-ch NOT, 1-ch 2-in AND, 1-ch 4-in OR, 1-ch 7-in OR (or similar combinations – some 3-in cascades), 1-ch BUFFER
  2. 3,0 to 3,3V operating voltage – 5,5V max, for derating
  3. 30ns pulses every 500ns should be possible
  4. Low power 1-2mW for logic, in total there will be max. 25 logic gates, so avg. each shall <30uA
  5. SC-70 seems to be ok – or are there more common footprints? Space shouldn’t be a big problem here

 

Would be nice to get your thoughts at this topic. Maybe we can set up a little call?

  • 0
    Guru 243820 points

    1. NOT: 74xx04, 74xx14 (Schmitt-trigger input); AND: 74xx08; OR: 74xx332, 74xx4075, buffer: 74xx34, 74xx125

    2. The only little-logic families are LVC and AHC. For larger devices, use HCS. AHC=VHC=NC7S=TC7PH=TC7S=TC7SH; LVC=LCX=NLx7SZ=NLx7WZ=NC7SZ=TC7PA=TC7SA=TC7SZ=TC7WZ.

    3. The propagation delays are smaller than 30 ns.

    4. Leakage currents are greatly affected by temperature. Do you have a known upper limit? The AUP family uses less power, but does not support 5 V.

    5. Both SC-70 and SOT-23 are common. SC-70 is more common due to its smaller size, but this means that there is less stock at the moment.

  • 0
    TI__Guru* 96591 points

    Hey Frank,

    In addition to the helpful suggestions from Clemens, I would also recommend to consider using dual footprints when possible.

    It generally takes little extra effort to have two package options per socket, and this provides a much broader array of options for filling said socket in the event of shortages. In most logic use cases, the added stubs/traces won't affect signal integrity enough to make any significant impact. We recently released a short app note on this topic here: Optimizing Board Space for Discrete LOGIC Designs Using Smallest Package Solutions

    Sticking to non-proprietary packages also helps.

    For 14-20 pin logic, I'd say to use PW (TSSOP) and BQ (WQFN, TI package names are BQA, BQB, and RKS) as they are relatively small options that are still very popular and available from multiple suppliers.

    For the smaller logic, 0.65 pitch (DCK, DCT)  and 0.95 pitch (DBV) packages are the most popular, but fitting both on a single footprint is a tight squeeze. If you go with DBV and DSF or DPW, you can fit both easily (although soldering a DSF or DPW by hand is quite challenging).

    -

    TI will continue to make CMOS logic devices for a very long time -- the HC family is over 40 years old and we're still improving and adding to it today. I can't speak for our competitors, but I suspect that they will continue to make these parts also as long as they remain popular.

    I would recommend to avoid the older, less popular families -- particularly bipolar logic (7400, 74S00, 74LS00). There just aren't many people willing to use up 30+mA of their power budget for a single logic gate anymore, so those aren't seeing as much use and I expect one day may be gone entirely.