LDO regulator and capacitors

Discussion in 'General Electronics Chat' started by ArchillesElbow, Jun 11, 2012.

  1. ArchillesElbow

    Thread Starter New Member

    May 2, 2012
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    Hi,

    If I am using a lithium polymer (lipoly) batter (4.2 - 3.7ish volts) as my source...into a module that needs 3.3v do I need to use a capacitor on the output side of my ldo if I am using a Mcp1701 (3.3v) low voltage regulator, or can I do without it? I need a stable 3.3v with around 250mah...

    Thanks!
     
  2. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Read the datasheet, if it says you need it then you need it, otherwise the regulator is likely to oscillate.
     
  3. ArchillesElbow

    Thread Starter New Member

    May 2, 2012
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    I tried it anyway on a test circuit...the current fluctuates between 1.6 and 2.2 volts.. The output should be 3.3.. So I guess I need to put in a capacitor...
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    Datasheets always have those answers spelled out.
     
  5. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    That would be voltage fluctuates..
     
  6. ArchillesElbow

    Thread Starter New Member

    May 2, 2012
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    Sorry meant voltage,, not current... I assume the current would fluctuate too tho,,,
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Yes current would fluctuate too, but current is measured in amps and voltage in volts ;)
     
  8. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    I wrote them for 25 years and most days was convinced I was the only human on earth who ever read them.:eek:

    Using the wrong capacitors causes virtually any LDO regulator to oscillate.
     
  9. ArchillesElbow

    Thread Starter New Member

    May 2, 2012
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    I think u r right:)
     
  10. atferrari

    AAC Fanatic!

    Jan 6, 2004
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    Questions like the one in the OP usually come from not reading the respective datasheet.

    RTFM should be compulsory by law. Lot of posts would not see the light.
     
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