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I am taking 12V from Power card to my backplane card to use for Hard disks. I have been advised to put decaps of 330 uF on 12V supply. Can I use 220 uF or even lesser value. What is the criteria for selcting the value 7 what other parameters should I check??

Oshi
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1 Answers1

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Unfortunately, there only correct answer to this is "read the datasheet". Lacking a datasheet, you need to have knowledge of the current draw characteristics of the specific hard disks you're using. Lacking that, you're left with trial-and-error.

Assuming you're in the trial-and-error boat, put the 220uF capacitor on there and see if it works. If you get strange behavior, increase the capacitance. You can't really go too high on a decoupling capacitor, so it's safer to err on the high side.

Dan Laks
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  • The Datasheet doesn't state about the capacitor to be placed. The problem is that in 330 uF & 12 V , the electrolytic are too big for my board size. I want to reduce the size of the caps. I tied for tantulum but not much difference. – Oshi Nov 03 '14 at 09:21
  • I don't know what your size limitations are, but you can use several smaller capacitors in parallel. That's actually beneficial in a way because the total ESR is reduced by the parallel resistance equation. – Dan Laks Nov 03 '14 at 15:41