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Caps to reduce noise

Discussion in 'Electronic Basics' started by [email protected], Jan 11, 2009.

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  1. Guest

    Hi All
    I’ve seen that everybody put a 0.1uF Capacitance and some other a
    0.01uF and a 0.1uF Capacitance near each IC in their board to reduce
    noise.
    But I’ve never seen an article that discusses how to calculate the
    capacitance that is needed.
    Do you know a formula to calculate the capacitance that is needed or
    an article that discuss the caps that is needed?
     
  2. Jasen Betts

    Jasen Betts Guest

    download the maker's data-sheet and use whatever they suggest.
    (using too much is unlikely to cause problems)

    Otherwise you have to figure out how big the current spikes are going
    to be and how much capacitance is needed to cater for them.
     
  3. Rich Webb

    Rich Webb Guest

    Go to http://www.intersil.com/support/techdocs.asp?x=AppNote and get app
    note AN1325 "Choosing and Using Bypass Capacitors."
     
  4. Jamie

    Jamie Guest

    A reservoir cap is placed at the rail lead to help maintain variations
    due to board rail feeds and inrush currents. This cap is normally a
    larger value how ever, these caps don't anything for R.F. issues
    because they tend to become inductive, thus, a smaller non inductive
    type may also be coupled with the reservoir type to bye pass the RF to
    ground.
    .01 is common for this in ceramic types.

    1 uf and up for reservoir use and normally are
    tantalum or electrolytic.

    P.S.
    Tantalums are smaller but tend to destroy them self in
    flames and smoke.

    Maybe if you make previsions to not allow the smoke escape,
    you can use those!

    http://webpages.charter.net/jamie_5"
     
  5. Eeyore

    Eeyore Guest

    Not noise, but power supply 'bounce' as current is drawn.

    It's largely empirical.

    Graham
     
  6. Eeyore

    Eeyore Guest

    ..01 WHAT ?

    Jeez, you need to grow up.

    Graham
     
  7. Jamie

    Jamie Guest

    I think you have a kink in your neck. You're look the
    wrong way.

    http://webpages.charter.net/jamie_5"
     
  8. neon

    neon

    1,325
    0
    Oct 21, 2006
    there is as somebody allready mention some guidelines as AN1325 .That is a guideline simply adding caps across IC is a normal procedure ruther having none and gremlins noise.
     
  9. Guest

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