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TLV62568: SW output resonate

Tyrone Liu
Prodigy 200 points
Part Number: TLV62568

Hi,

I found my buck circuits based on TLV62568 have something wrong, that the SW output resonate, like below waveform capture. 

Please comment the possible causes and solutions, thansk.

My concern: I design the circuits based on peak Iout 0.6A, while the actual mean load current is about 0.15A.

  • 0
    TI__Expert 8756 points

    Hello User,

    Can you share where did you take the GND connection for the measurement?  Can you also share the PCB layout?

    Thanks!

    Best regards

    Sneha 

  • 0 in reply to Sneha
    Prodigy 200 points

    Hi Sneha,

    Here is the PCB layout, the feedback resistors and enable delay RCs are on the opposite side and not showing.

    I connceted the ground through pin 2 of C185 with ring ground probe,when measurement.

    TLV62568 Layout

    BR 

    Tyrone Liu

  • 0 in reply to Tyrone Liu
    TI__Expert 8756 points

    Hi Tyrone,

    Can you please check again with the GND connection somewhere near to the SW node pin. You can solder a connector to some point near to SW pin and measure. (see below)

    I am expecting the behaviour could be because of the longer GND loop which can introduce noise in the measurement. Apart from this, I do not see any issue with the schematic and layout.

    Thanks!

    Best regards

    Sneha

  • 0 in reply to Sneha
    TI__Expert 8756 points

    Hi Tyrone,

    Do you have any update on this? let me know. If not, please close this thread by clicking on "Resolved" button.

    Thanks!

    Best regards

    Sneha 

  • 0 in reply to Sneha
    TI__Expert 8756 points

    Hi Tyrone, 

    If there are no further questions here, I will close this thread now. In case of further questions, you can re-open it by posting your comments below.

    Thanks!

    Best regards

    Sneha

  • 0 in reply to Sneha
    Prodigy 200 points

    Hi Sneha,

    Sorry for the late reply. The issue of SW output resonate is just because this buck chip turns into power save mode at light load condition, like the Application Performance Curves in datasheet and as below.