TTL Hi Input

Discussion in 'General Electronics Chat' started by jugheadkills, May 7, 2008.

  1. jugheadkills

    Thread Starter New Member

    May 7, 2008
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    Most data sheets give information on the minimum hi TTL input.

    What about the Maximum high? The same as VCC?
     
  2. jugheadkills

    Thread Starter New Member

    May 7, 2008
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    What if my input signal is higher than VCC?
     
  3. Audioguru

    New Member

    Dec 20, 2007
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    The datasheet for an old Texas Instruments TTL IC says it blows up when its input voltage is higher than +5.5V.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
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    It is always safest if you avoid taking an input to a voltage greater than the Vcc. However there are devices which are designed to permit the input to be greater than Vcc. Consult the manufacturer's datasheet to determine the maximum input voltage.

    hgmjr
     
  5. mik3

    Senior Member

    Feb 4, 2008
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    Usually is the same as Vcc but if you have a higher input voltage you have use a voltage divider to reduce it to the logic levels.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    You could use a couple of 4.7v Zener diodes to clamp the inputs to ground and +5v if necessary.

    See the attached example.
     
  7. jugheadkills

    Thread Starter New Member

    May 7, 2008
    3
    0
    Thanks for the responses.
     
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