• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 63 subscribers
  • Views 539 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

LM21305 step-down converter no entering in DCM with no load

Sylvain Poulin
Prodigy 110 points
Other Parts Discussed in Thread: LM21305

Hi,

I have a design with the LM21305... On two different boards, both with no load, one is in Discontinuous Mode and the second is in continuous mode (negative current in the inductor).

Is anybody have seen that problem before ? The one in Continuous Mode has a higher temperature but still regulate the output voltage to 4V. The input voltage is 15V.

Thanks,

Sylvain

 

  • 0
    TI__Guru 67712 points

    Hi Sylvian,

    The inductor peak-peak ripple current in your design is approximately 1A, so it's possible that you could observe -0.5A inductor valley current at no load based on threshold variation of the zero-cross detection circuit (related to MOSFET Rdson), the repsonse time of the zero-cross comparator, and the di/dt associated with the inductor current downslope, Vout/L. However, the temperature increase at no load should be minimal.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    Prodigy 110 points

    Thanks Tim for the answer, the temperature increase is around 5ºC in comparison to a board that goes in DCM... I can leave with that.

     

    Regards,

     

    Sylvain