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TPS54331: TPS54331DR as 5V to 1.2V buck convertor and output 1.2V have big over shoot problem!!!

Cheney_Sun
Intellectual 595 points
Part Number: TPS54331

Hi TI EE：

               I am using TPS54331DR as 5V to 1.2V buck convertor,and when 5V  power off ,1.2V output have big ripple and 1.2V output can run to 1.6V.

              My circuit as bellow:

The waveform as bellow

CH1:5V Vin CH2:TPS54331DR Comp Voltage CH3:TPS54331 Vsense CH4:1.2V Vout

When 5V Vin shutdown with ripples,and 1.2V Vout also have ripple and the 1.2V Vout over shoot can as high as 1.6V.

Zoom the 1.2V Vout Over shoot waveforms as bellow :

CH1:5V Vin CH2:TPS54331DR Comp Voltage CH3:TPS54331 Vsense CH4:1.2V Vout

Please help to solve the 1.2V Vout Over shoot problem ASAP.

Thank you very much.

BR

Cheney_Sun

  • 0
    TI__Genius 10070 points

    Hi,

    The inductance is a little large, it would be better to change it to 2.2uH. But I don't think the issue is caused by the inductor. Could you please share the layout? Let's review it.

    And please test SW waveform, it would be better for us to understand what happened during shutdown. 

    Shawn

  • 0 in reply to Shawn Nie
    Intellectual 595 points

    Hi Shawn:

                    Thank you for you reply.

                   The normal waveform as below when 5V VIN is stable.

    CH1:5V Vin CH2:Vboot to GND Voltage CH3:Vcomp to GND Voltage CH4:1.2V Vout

    When 5V Power off,and the 1.2V Vout over shoot waveform as bellow :

    You can see that 1.2V Vout can get to 1.673V

    CH1:5V Vin CH2:Vboot to GND Voltage CH3:Vcomp to GND Voltage CH4:1.2V Vout

    Please help me to solve the overshoot problem.

    Thank you!

    BR

    Cheney_Sun

  • 0 in reply to Cheney_Sun
    TI__Genius 10070 points

    Hi,

    As I mentioned, could you please share the layout? If the layout is not good, and it is easy to introduce noise.

    And where the 5V voltage comes from? How did you do the shutdown test?

    Shawn

  • 0 in reply to Shawn Nie
    Intellectual 595 points

    HI Shawn:

                   I have solved the problem.Thank you all the same