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Original question:

TPS43061: Subharmonic oscillations and inductor overheating

TPS43061: Subharmonic Oscillation Happen

Victory Loh
Prodigy 60 points
Part Number: TPS43061

Hi,

I am using TPS43061 in my project.

Vin : 12V to 16.4V

Vout : 36.5V

Peak Power : 360W

I face subharmonic oscillation at 14.4Vin and below when load at around 4A.

I wish to add external slope compensation circuit to counter back the subharmonic oscillation.

Do you have any application circuit that can realize the design?

Best regards,

  • 0
    TI__Guru* 75630 points

    Hi,

    Thank  you for designing with the TPS43061.  Could you reduce the current sense resistor by 50%, which would make the internal slope compensation to be relatively more stronger. 

    Thanks,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 60 points

    Hi, 

    My current design Rsense resistor value is set at 1.42mΩ. 

    Inductor value is 4.7uH.

    In this case, let me try to further lower down the Rsense value and test out the design.

    Thanks!

  • 0 in reply to Victory Loh
    TI__Guru* 75630 points

    The 1.42mOhm sounds already small.  I am afraid this is not related to slope compensation.  Could you share your schematic and some key waveforms that can show the issue?

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 60 points

    Hi, 

    We found out that the subharmonic oscillation was cause by the RT/CLK loop as we external solder out wire and connect to external PCB for Rt tuning.  

    Finally, we tuning Rt by directly mount the resistor near to IC pin and the problem is solved.

    Attach is the schematic for TPS43061 for our application.

  • 0 in reply to Victory Loh
    TI__Guru* 75630 points

    Hi Victory,

    Thank you for the update and congratulations for your resolving of the issue.  You are right that the RT resistor should be closely placed by the IC.  Please also read the datasheet layout guidelines when you re-design your PCB. 

    Let me close this thread here. Please feel free to contact us if we can be of further assistance. 

    Thanks,

    Youhao