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  • lm339
Related

LM 339 Comparator Question

jw0752
jw0752 over 10 years ago

Does anyone know if the unused inputs of an LM339 quad comparator need to be stabilized and if so what is the procedure? Since the outputs are open collector I suspect it is ok to leave them floating. I have checked my data sheets but I can't find anything about the unused inputs.

 

Thanks John

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  • dougw
    dougw over 10 years ago +1 suggested
    It should be okay to leave them floating - there should be no excessive current conditions, but it looks like the internal circuit might use a bit more current when the output is low - it is hard to tell…
  • johnbeetem
    johnbeetem over 10 years ago +1 verified
    I would suggest pulling up the unused +in and pulling down the unused -in. That way your open-collector outputs are switched off and there's no internal switching generated by noise. JMO/YMMV
  • D_Hersey
    D_Hersey over 10 years ago +1
    Often, John, upon a little meditation, we can find a use for those unused comparators. They can be used to set up a warning light with an LED, for example.
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  • johnbeetem
    0 johnbeetem over 10 years ago

    I would suggest pulling up the unused +in and pulling down the unused -in.  That way your open-collector outputs are switched off and there's no internal switching generated by noise.

     

    JMO/YMMV

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  • jw0752
    0 jw0752 over 10 years ago in reply to johnbeetem

    Thanks John,

    This makes the most sense to me. The section will be turned off and stable.

    John

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  • jw0752
    0 jw0752 over 10 years ago in reply to johnbeetem

    Thanks John,

    This makes the most sense to me. The section will be turned off and stable.

    John

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