Push-Pull logic with weak pull-up?

Discussion in 'General Electronics Chat' started by Selmesal, Oct 4, 2016.

  1. Selmesal

    Thread Starter New Member

    Oct 4, 2016
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    Is it possible to have a weak pull-up with a push-pull configuration?
    Are there any benefits to doing so?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,179
    1,800
    Well sure. If you turn off both halves of a complementary output, you have an input with a weak pullup. Seems like the standard port configuration for an Atmel part,
     
    Selmesal likes this.
  3. Selmesal

    Thread Starter New Member

    Oct 4, 2016
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    Thanks!
     
  4. Selmesal

    Thread Starter New Member

    Oct 4, 2016
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    Is an input with a weak pull needed only when you drive it with an open drain configuration?
    (i.e. if the input signal was driven by a push-pull, would you still need a pull-up on the input pin?)
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    if you allways drive an input pin with a push-pull output, and both devices are allways on at the same time, then the pullup is not needed and just wastes power.
    Weak pullups allow for only very slow signals, but consume very little power. For higher speeds you would usually need a stronger pullup outside the chip.
     
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  6. Selmesal

    Thread Starter New Member

    Oct 4, 2016
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    Thanks!
     
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