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Repairing a motor control board from a washing machine. A 1206 ceramic cap was burned up, there's a bulk electrolytic in parallel, rated 200v 1000uF. I've attached the example schematic for the ic (IRDAKO726350B) and circled the area in question. Replace with typical 100nF? Is there a downside to putting in a 1uF? I have ceramic caps rated to 500v.

datasheet link: https://datasheet.octopart.com/IRDAKO726350B-Infineon-datasheet-82521255.pdf

enter image description here

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  • \$\begingroup\$ Do you have voltage rating on said ceramic to match up? Then I see no problem. \$\endgroup\$
    – winny
    Sep 21, 2018 at 12:19
  • \$\begingroup\$ @winny I have some 500v ceramics \$\endgroup\$
    – Dan
    Sep 21, 2018 at 12:21
  • \$\begingroup\$ Should be plenty! Go for it. \$\endgroup\$
    – winny
    Sep 21, 2018 at 15:05

1 Answer 1

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Look at the wording in the 2 points from your screenshot.

In point 1, which talks about the BUS capacitors, which is what your question is about, it states that additional high frequency capacitors mounted close to the pins will improve performance.

In point 2, about the decoupling capacitors, it mentions the same. It uses the same phrase:

high frequency capacitors

and then states

typically 0.1uF

So, it would be safe to assume that using a 100nF capacitor on the bus line will be fine. If you are unsure, stick an additional 1uF in parallel with it. But yes, a 100nF should be fine. Make sure that it has the correct voltage tolerance though!

Just remember that there would be a reason this component would be burnt up. Replacing this capacitor may not be a fix, and there could be an underlying issue that requires further investigation.

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  • \$\begingroup\$ Yes, perhaps I should have circled to indicate that I had read the 0.1uF guidance, as why I included it. There are several burnt up components, chief being the IC itself (shorts annotated on graphic in blue), and the current sense resistors coming off P17/19/21. \$\endgroup\$
    – Dan
    Sep 21, 2018 at 12:16
  • \$\begingroup\$ Ahh, then yes, looks like there is still a bit more to do! Good luck with figuring out the source issue! \$\endgroup\$
    – MCG
    Sep 21, 2018 at 12:49

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