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TPS54388C-Q1: TPS54388 output voltage vibration

Imelda Zhang
Expert 3375 points
Part Number: TPS54388C-Q1

We are using TPS54388C generate UG1V form UG5V. Relevant schematic as attachment.

I have measured TPS54388C output voltage vibration during SCH UG1V.pdfrise time.

Do you have some ideas about this issue?

SCH is attached

 

  • 0
    TI__Genius 12400 points

    Hello Imelda,

    Let me look at the issue, I will get back to you tomorrow.

    Thanks,

    Farheen

  • +1 in reply to Farheen
    TI__Genius 12400 points

    Hello Imelda,

    It seems like this is due to the pulse skipping behavior and it is normal to see this. Once the Vout is above the minimum voltage limit because of the minimum on time, it should be okay. For this device, minimum voltage limit is 800mV. After the 800mV, you see that there is no ripple.

    There are different ways that can help to reduce this ripple in output voltage during startup:

    1) Increasing the COMP cap value (C53502 in your case)

    2) Also playing with passive components can help (e.g increasing the output cap can help to reduce the ripple or increasing the inductor value)

    This application note (https://www.ti.com/lit/an/slva866a/slva866a.pdf) explains this in detail.

    So I will suggest to play with these options to find the right configuration.

    Thanks,

    Farheen