Logic family outputs

Discussion in 'General Electronics Chat' started by nDever, May 18, 2012.

  1. nDever

    Thread Starter Active Member

    Jan 13, 2011
    154
    4
    Hey guys,

    I remember reading somewhere that a general rule for circuit design involving logic chips is that all inputs, regardless of whether a particular input is used or not, should be connected to something (GND or Vdd). What about outputs? What if I don't plan to use all of the outputs on a particular chip? Can I leave these open?
     
  2. Wendy

    Moderator

    Mar 24, 2008
    20,766
    2,536
    Outputs do not matter. Some families, such as TTL, will assume a logic level on open inputs, Others can't.
     
  3. MrChips

    Moderator

    Oct 2, 2009
    12,442
    3,361
    You DO NOT connect unused outputs to VCC, VDD or GND. You will end up consuming excessive current and in danger of blowing your chip.
     
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