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74HC14 Schmitt Trigger

Discussion in 'General Electronics Discussion' started by AmandaM, May 26, 2015.

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  1. AmandaM

    AmandaM

    21
    3
    May 15, 2015
    Hello Again

    Very quick question this time. Should I tie the unused inputs of the 74HC14 Schmitt Trigger to ground or are they ok left floating?

    Many thanks
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Tie them to ground, Vcc, or any other source of a valid logic level. The first two are preferable, but the third can be an option if routing is an issue.
     
  3. HellasTechn

    HellasTechn

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    Apr 14, 2013
    With digital electronic chips it is better if you ground the unused inputs. Left floating may be ok or may produce errors
     
  4. AmandaM

    AmandaM

    21
    3
    May 15, 2015
    Thanks all, as usual, it's appreciated. I will tie them to ground—I assume that they will not need a pull-down resistor?

    Thanks...
     
  5. poor mystic

    poor mystic

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    Apr 8, 2011
    No pull down is needed. Just straight to ground. :)
     
  6. kpatz

    kpatz

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    Feb 24, 2014
    If it's a production circuit that is stable (not undergoing revisions), you could tie the unused inputs directly to ground. But if it's a prototype, using a resistor (or a jumper) makes it possible to remove it if you need to use one of the unused gates in the future, instead of having to cut traces on a PCB.
     
    HellasTechn likes this.
  7. HellasTechn

    HellasTechn

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    Apr 14, 2013
    That is a good idea.
     
  8. Colin Mitchell

    Colin Mitchell

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    Aug 31, 2014
    Generally, with a Schmitt Trigger, it does not matter if the inputs are left floating because the hysteresis is about 30% of supply and gates will not self-oscillate. Tieing them HIGH or LOW does not affect the quiescent consumption.
     
  9. AmandaM

    AmandaM

    21
    3
    May 15, 2015
    Thanks everyone—your help and comments are appreciated.
     
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