Does a Voltage Regulator Draw Power at Rest?

Discussion in 'The Projects Forum' started by Dan-O, Jan 8, 2010.

  1. Dan-O

    Thread Starter Active Member

    Jul 26, 2009
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    I'll try to explain what I'm doing:
    I was using a 556 as a flip flop for a single button push button start for my car.
    The original design works but in the interest of having way fewer parts and because I'm a glutton for punishment, I found an EDE2208 which is a momentary-to-toggle IC. It seems like a perfect solution and even has switch debounce built in.
    Only one issue, and it actually might not be an issue: Because this is in a car I need to keep my at rest parasitic current draw to a minimum.
    I was planning on using a 5V + regulator powered all the time, but that's where my issue or concern is. Will a 5V voltage regulator draw an excessive amount of current if the 2208 is inactive or not powering/controlling a transistor?
    While I'm on the subject, could anyone recommend a good all purpose 5V + regulator? I was thinking a 78L05 would work, but the spec sheet is listing it maximum quiescent current as 5mA, it would be great if I could get it down more.

    I'm only going to be using 1 set of contacts, so I won't be over-working the regulator too much, right?
    Thanks for the input,
    Dan
     
    Last edited: Jan 8, 2010
  2. Wendy

    Moderator

    Mar 24, 2008
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    A voltage regulator will always draw some power. It is, after all, a circuit. But if there is no load it should draw very little.

    An LM317, a variable voltage regulator, draws around 10ma if there is no load.
     
  3. Dan-O

    Thread Starter Active Member

    Jul 26, 2009
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    I just need a fixed 5V to power the IC.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Yep, and whatever you use is going to draw something, be it a zener circuit or a 7805. The circuitry inside the 7805 needs some power just to maintain the voltage. I picked the LM317 because I knew its standby current, I'm not so sure about the 7805. I would guess a couple of ma.
     
  5. Dan-O

    Thread Starter Active Member

    Jul 26, 2009
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    The spec sheet lists quiescent current at 5mA.
    I can live with it, but I wish I could find lower.
    I was also thinking about powering my module through the battery saver section of my body module.
    The body module shuts down the OEM power relay after about 14 minutes. I just need to see if the power relay stays active during cranking.
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    I wouldn't be too surprised to find out the new generation low voltage drop chips draw even less. I'm not sure, but I think they use CMOS circuitry.
     
  7. Dan-O

    Thread Starter Active Member

    Jul 26, 2009
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    BTW Bill, thank you for the input and allowing me to bounce ideas off you.
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    My pleasure.
     
  9. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Google "low quiescent current voltage regulator". You can get 5V regulators with quiescent current on the order of a few microamps.
     
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