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MM74HC164 - Freq limits at 3.3V?

Discussion in 'Electronic Design' started by [email protected], Feb 12, 2007.

  1. Guest

    Hi,
    Im using MM74HC164 in my project as a serial to parallel converter and
    my question is if i give 3.3V as Vcc (supply voltage) what may be its
    operating frequency, can please some one help me out in finding this...
     
  2. On 11 Feb 2007 22:22:00 -0800, in sci.electronics.design
    It is in the datasheet, page 4 in the fairchild version, or maybe you
    didn't ask the right question


    martin
     
  3. There are logic families meant for faster operation at low supply
    voltages, than the old 74HC parts, . For example the 74vhc family
    is specified down to 2.0 volts. The 74vhc164 can shift to 125MHz
    typical (or to 80MHz minimum), at 3.3V and 25C, according to the
    datasheet, http://www.fairchildsemi.com/pf/74/74VHC164.html
     
  4. Fred Bloggs

    Fred Bloggs Guest

    Every datasheet known to mankind will list the maximum frequency versus
    Vcc in the "timing" section. First and foremost before undertaking a
    digital design is to learn how to read datasheets. How come you don't
    know how to do this?
     
  5. Well, Fairchild's 74hc164 datasheet doesn't say anything about
    operation at 3.3 volts. It says the worst-case minimum is 5 MHz
    at 2V, and 27 MHz at 4.5 volts, 25C. Such a huge spec variation
    from 5 to 27MHz makes it hard to estimate the operation at 3.3V
    and is one good reason to simply avoid using the hc logic family
    at low voltages. This is especially so when there are plenty of
    much better choices, like the 80MHz at 3.3V 74vhc164 I suggested.
     
  6. OK, maybe it's not quite that simple. I see most distributors don't
    carry the 74vhc164. DigiKey and Newark don't, although Mouser does.
    The 74ac164 could be an alternate choice, DigiKey and Mouser have
    it, although Newark doesn't. The 74ac164 is spec'd at 62MHz min at
    3.3V for the -40C TO +85C temp range. Hell, it'll even do 7Mhz at
    1.5 volts. Now that's getting doowwn!

    BTW, when it comes to finding the logic families you want in stock,
    it gets rather difficult if you insist on a particular IC package.
    For example, I like the thin ssop SMD package, TSSOP, which is both
    space-saving and reasonable to hand solder. But many MSI parts are
    not offered in that package, or if they are, they're not stocked.
     
  7. Joerg

    Joerg Guest

    Winfield Hill wrote:


    [...]

    Man, you must have good eyes. In my designs I need to use TSSOP a lot
    but really hate it when I have to swap one of these out.
     
  8. It's not so bad if you're using a Metcal soldering station
    and have a Talon handle (which has two tips), with the right
    tip, TATC-502. The whole IC comes off at once in a hurry.
     
  9. Riscy

    Riscy Guest

    This family should work both 5V and 3V3 system
     
  10. Yes it works, but not well.
     
  11. Joerg

    Joerg Guest

    I've used HC logic under 3V, a lot. Ok, it becomes a bit sluggish but
    sometimes there isn't much of a choice when you want widely available
    parts. For example, right now I need an 8-bit equality comparator and
    other stuff for bus slot and address detection. There ain't much else in
    stock than HC688 and the like. The other guys want to run the bus at
    3.3V. It's spec'd at 2V and 4.5V but not at 3.3V so I must probably use
    the 2V spec unless I find one that has 3.3V in the data sheet.

    Guess I'll have to post a speed limit on the bus, hoping the other guys
    won't pelt me for that ;-)
     
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