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Is a voltage regulator always required?

Discussion in 'General Electronics Discussion' started by Crogdor, Jun 19, 2013.

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  1. Crogdor


    Jun 7, 2013
    I'm wiring up an ATMEGA328P-PU to a breadboard.

    I've got a 5V 20A regulated switching power supply to provide power. Is there any argument for wanting a voltage regulator, as the supply is already regulated at 5V?

    I ask because looking at the circuit diagrams for this chip shows that people are using regulators like the 7805 or 2940. As I was researching those components, I learned about dropout voltage, and it would seem that neither the 7805 or 2940 would work as they would require 7V or 5.5V input voltage respectively, and my PSU is outputting 5V.

    (Well, actually I suppose the 2940 would work, as I can dial up the PSU voltage by up to 15%, but let's pretend that isn't an option for the sake of my question.)
  2. BobK


    Jan 5, 2010
    Let's see. You have a regulated supply. And you add a regulator. Now you have a regulated supply. Do you have to add a regulator to it? When do you stop?

    (No, you do not need another regulator if you already have a 5V regulated supply.)

  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    There should be no need unless the 5V is dirty.

    That may be the case if you have other loads on the 5V rail (especially heavy ones).

    If that is the case then you may be able to get away with something as simple as a schottky diode and a capacitor, or possibly an inductor and a capacitor (LC filter).
  4. Crogdor


    Jun 7, 2013
    Thanks for the replies!
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