• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 30 subscribers
  • Views 1473 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8353: Replace flying 47uf charge pump capacitor with 100nf

Marshall Scholz
Prodigy 20 points
Part Number: DRV8353

I would like to reduce my bom count on my drv8353 design.

The 47nf cap you recommend for the flying charge pump is unique, while I have many 100nf caps of the same voltage rating/package throughout my design.

Will switching this charge pump cap to 100nf cause unstability or damage (aka, with excessive current or such) to the drv8353 at all?

Also, I believe I have found a mistake in your datasheet.

In your example layout, the bootstrap cap for the buck converter is attached between VIN and BST, where it should be between SW and BST.

This conveniently makes the example layout much nicer, while in actuality the layout is much messier as you can't squeeze 2 traces under the cap.

  • 0
    TI__Guru 65410 points

    Marshall,

    Thanks for posting on the MD forum!

    The design of the charge pump unfortunately relies on the 47nF and this should not be changed. That being said if you really must use 100nF then you could use two of them to make an effectively 50nF cap on that node. Of course it's recommended that you use the 47nF suggested.

    You are correct, that diagram has an error, I will get that corrected.

    That being said, using the same diagram, you could use the existing VIN via for input power and bring the SW node down slightly to meet the existing BST cap placement. 

    Like this:

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 20 points

    Thanks, I was hoping the 100nf would just be an easy swap, but if the design requires it, I'll keep the 47nf.

    For the example layout,

    that is close to what I ended up doing, but the other thing with the example layout is that isn't there supposed to be a capacitor close to Vin since it supplies the buck switch node?

    The closest capacitor is 15-20mm away as part of the vm supply.

  • 0 in reply to Marshall Scholz
    TI__Guru 65410 points

    Marshall,

    You are correct, please check the EVM layout here for a different example and a known tested board:

    http://www.ti.com/lit/zip/slvc742

    Regards,

    -Adam