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TPS51219: Phase waveform shift issue

Edward Lee
Intellectual 1655 points
Part Number: TPS51219

Hi Sir,

  

    My customer recently encountered a switching waveform problem with TPS51219.

    The configurations are listed below.

     1. Operate TPS51219 in D-CAP2 mode

     2. Switching freq is 500KHz and current sense from Rdson

     3. Test condition is Vin=5V while vout =1V at 23A

   

    The customer captured the phase waveform and found there seems to be periodically phase shift at the switching node.

     May find the waveform below. They captured it in infinite acquisition and can find the phase shifted.

     Would you kindly advise what may cause the problem and help us to improve it?

Thanks

Sincerely,

Edward

  • 0
    TI__Mastermind 18510 points

    Hi Edward,

    Only 5V to 1V/23A see this phenomenon? if smaller loading or higher Vin, whether it can be see as well?

    Also please confirm this is not OSC trigger issue, lower the trigger point to 50% of the rising to check it. And Zoom in to check only 2 cycles.

    If it exactly happen the this.Upload your schematic/layout for review.

    Yuchang

  • 0
    TI__Guru 56865 points

     

    The "periodic shift" that you are seeing appears to be a result of you having the edge trigger for the Oscilloscope set to close to the peak voltage on the sampled signal, so the trigger is occationally triggering on the rising edge of the SW voltage instead of the falling edge.

    If you reduce the trigger level to 1/2 of the input voltage, you should see this issue resolve itself.