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UCC28881: UCC28881

Tsion Bublil
Prodigy 20 points
Part Number: UCC28881

Hi

My application is converting from 270V DC at the input to 6V DC at the output. I got the UCC28881 evaluation board and I test it on my system and it works fine.

I try to built a board with SMT components which have the same values as the components at the evaluation board.

The problem is that I got 2V DC at the output and decreasing slowly to 0V.

Please see my draw, can you help me find my mistake

Thanks in advance

Tsion

  • 0
    TI__Guru 66135 points

    Hello,

    I don't see your attached schematic for your design. 

    If you send one I can review it?

    You mention that your design is same as the evaluation board and does not work.

    This could possible be a layout issue or a connection issue.

    Please double check your schematic of your design and compare it to the reference design to see if any connections or components are different.

    In regards to the layout there is section in the data sheet 11.2 that gives tips for a good layout as well as an example that  might help.

    Regards,

  • 0 in reply to Mike O'
    Prodigy 20 points

    I try again to attach my draw, can you see it? I try upload PDF file

    if not, can you send mail address?

    270 Reg Ver2.pdf

  • 0 in reply to Tsion Bublil
    TI__Guru 66135 points

    Hello,

    The schematic came through fine  I reviewed the schematic and it looks O.K.

    You mentioned that you had the design working with a modified EVM and it worked fine.  The data sheet for the output filter inductor looked O.K. and I would think it should work.

    It could be your layout.  I would suggest studying the layout to ensure it matches your schematic and is similar to the EVM.

    The specs for the output inductor L1 look like it should be able to handle a 225 mA output load current.  Just double check you might want to try this inductor in the EVM to make sure it works.

    Regards,