What does this mean in a schematic?

Discussion in 'General Electronics Chat' started by wubs, Mar 26, 2009.

  1. wubs

    Thread Starter New Member

    Mar 22, 2009
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    I saw in a schematic the following notation which means to me that I would place the capacitors in series, but am not sure.

    The circuit is for a step-up DC-DC circuit.

    The capacitor in question is shown only once and the lable for it is "C4 2x 4.7uF". I am assuming this is done because there is no one standard value available, so this is a way to acheive the desired value?

    Please help, I cannot construct it until I know if I should wire it in parallel or in series.

    Thanks in advance!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    One interpretation is that C4 is actually two 4.7 uF caps. They may go in parallel, but it's impossible to do more than guess without a schematic to see.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    They could also be back to back, which allows polarized caps to be non polarized.
     
  4. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    In addition to beenthere's comment, that notation is quite common in power supply schematics and usually means to put the capacitors in parallel. It is often on the input side of the regulator and is to reduce ESR.

    However, the only way to be sure is if you post or link to the schematic.

    John
     
  5. wubs

    Thread Starter New Member

    Mar 22, 2009
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    Here's the schematic.

    I've circled the component in question so that you can spot it right away.

    As well as explaining why someone would put in such a notation ("2x 4.7uF") feel free to comment on improvement or corrections to the circuit.

    Thanks again!
     
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    That means in parallel, which lowers the ESR.

    John
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    The schematic is implying to use 2 4.7uF in parallel, I am unsure why.

    A 22uF is shown in the output, but there are no polarity markings as in the one circled. Is that supposed to be 2.2uF ceramic?

    A 4.7uF Electrolytic has a much higher (nearly 10x) ESR than a 22uF. I'm not sure why two 4.7uF electrolytics would be used unless they had a batch of them left over from a previous manufacturing run.
     
  8. wubs

    Thread Starter New Member

    Mar 22, 2009
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    The 22uf cap (C5) is not used. Apparently that was never corrected in the schematic.

    As for C4, it is supposed to be 2x 4.7uF SMD Tantalum capacitors (reading from top to bottom, they seem to say "226 35K 852" on them), but I was told it is OK to use electrolytic if they were handy.
     
  9. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    First you need to get your Captain Marvel secret decoder ring.

    226 = 22X10E6 picofarad or 22 microfarad
    35 is the voltage rating, i.e., 35V (the K is probably for Kemet)
    852 is a date code (probably)

    So, your circuit has 22 uF capacitors on it already. It is quite fun reading about the various codings and types of capacitors within a general class, if you like details.

    Here are links to two large manufacturers. I suspect yours may be a Kemet brand. See if you can decipher the date code.

    http://www.kemet.com/
    http://www.avx.com/

    John

    Edit: Here's a clue, it looks like it was made in December, if the coding is consistent with Kemet's coding for SMD tantalums.
     
    Last edited: Mar 26, 2009
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