Unused Inputs

Discussion in 'General Electronics Chat' started by ricker24, Apr 13, 2011.

  1. ricker24

    Thread Starter Member

    Mar 5, 2011
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    I need to know if you always need to ground all unused inputs on an IC? I am using a 4011 and am not using all the inputs. Thanks...
     
  2. Jony130

    AAC Fanatic!

    Feb 17, 2009
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    Connect all unused inputs of a 4011 to Vcc.
     
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  3. SgtWookie

    Expert

    Jul 17, 2007
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    All unused inputs for a CMOS IC need to have a current path to ground or Vdd. They can be connected directly, via a resistor, etc - but if they are left disconnected, they can oscillate at unpredictable frequencies, causing strange problems.

    Unused OUTPUTS should be left disconnected.
     
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  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Typically the datasheets will recommend treatment of unused pins.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    This is not generally the case for 4000 series CMOS.
    They usually don't mention the bypass capacitor requirement either.
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    While I use your idea of a bypass capacitor for every IC, the "CMOS Cookbook" says to use one capacitor for every six IC's.
     
  7. ricker24

    Thread Starter Member

    Mar 5, 2011
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    Thanks guys. Thats what I thought but just wanted to make sure so I didn't cook something....
     
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