Because of the holidays, TI E2E™ design support forum responses will be delayed from Dec. 25 through Jan. 2. Thank you for your patience.

  • State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 65 subscribers
  • Views 1313 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPS54560: Pulse skip mode during heavy load

Kuramochi Tadahiko
Guru 28715 points
Part Number: TPS54560

Hi,

TPS54560 work as pulse skip mode during heavy load on the EVM changed output voltage setting to 24V.

When output voltage setting change 5V, pulse skip does not occur.

This defect also occurs on my customer's board and occurring probability is 0.78%(4/507).

Has anyone ever seen such defect ?

What is this defect caused by?

Best regards,

Kuramochi

  • 0
    TI__Guru**** 191445 points
    Can we see the schematic? Did ou change the compensation when you changed the output voltage?
  • 0 in reply to JohnTucker
    Guru 28715 points
    John-san,

    Thank you for quick response.

    Could you send me email? kuramochi@fujiele.co.jp
    Or please tell me your e-mail address.

    Best regards,
    Kuramochi
  • 0 in reply to Kuramochi Tadahiko
    TI__Guru**** 191445 points
    I can take a quick look at it, but I don't support TPS54560 directly. Then I will forward it to the correct person.
  • 0 in reply to Kuramochi Tadahiko
    Guru 28715 points

    John-san,

    I send schematic.

    > I don't support TPS54560 directly. 

    I got it.

    >Did you change the compensation when you changed the output voltage?

     I don't know setting value of compensation in a detail on the EVM.

    However compensation component looks like that there is traces such as changed.

    I post an additional information.

    Though I observed load transient response on EVM @Vout=24V, ringing is not captured.

    So I'm guessing that phase margin is enough.

    Best Regards,

    Kuramochi

  • 0 in reply to Kuramochi Tadahiko
    Guru 28715 points
    Hi,

    I'm hearing that John-san can not support this problem directly.
    Could any one help me?
    (I contacted with John-san via email. )

    Best Regards,
    Kuramochi
  • 0 in reply to Kuramochi Tadahiko
    TI__Genius 11085 points
    If you haven't make any changes on the EVM other than the feedback resistor to change from 5V output to 24V output, quite some things changed in the operation. The peak to peak current ripple will be larger, and that could be why the part enters pulse skipping mode at heavy load. When the ripple is too big, the peak current could trip peak current protection level at heavy load, then the part will pulse skipping.

    The output capacitor may be selected for 5V output, and they may have derated significantly with 24V output voltage.

    I'd suggest run a Webench design with your input/output condition with this device, modify the EVM components to the new design and test the operation of the device. Webench design input window locates at the right hand side of the product folder page
    www.ti.com/.../TPS54560