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Original question:

LM22676: Short circuit protection

LM22676: inductance current

WolfgangCS
Prodigy 20 points
Part Number: LM22676

Hello,
I have a question regarding the value of the inductance Isat current for LM22676.
If the max peak current limit of the LM22676 can be as high as 5.5A, shouldn't whatever inductance value you use still have the Isat of your inductor equal or greater than 5.5A?
If so, why is this specification not taken into consideration in the Webench Power Designer for the LM22676?

Thanks

  • 0
    TI__Genius 11991 points

    Hi，

    Yes, Isat of inductor should be greater than max peak current limit. Because inductance will decrease when inductor current meet Isat, it will cause inrush current in this situation.

    For Webench Power Designer for the LM22676, the specification of Isat has been taken into consideration. You should double click inductor, then different types of inductors can be selected as  shown below.

    B R

    Colin

  • 0
    TI__Genius 10390 points

    Hi，

    Yes, the Isat of your inductor should be greater than 5.5A.

    For the same inductance value, there are different inductor types to correspond to different Isat. So Webench Power Designer will give the appropriate inductance value according to the working condition. You need to consider both the Isat and Webench inductance value when finally selecting a specific inductor type.

    Best Regards,

    Aurora

  • 0 in reply to Colin Chen
    Prodigy 20 points

    Hi, 
    Thanks for the answer.
    I attach the webench design report that I am interested in. In this example I am shown an inductance with a value of 47uH, but its saturation current value is not greater than or equal to 5.5A. Shouldn't it already take this into account and show me an inductance with that value?

  • +1 in reply to WolfgangCS
    TI__Genius 11991 points

    Hi，

    Webench design will automatically match the output current with the Isat of the inductor. In your simulation model, you set the Iout to 1A, so there is no need for Isat to exceed 5.5A . If you change the output current to maximum Iout of 3A as below, then Isat of selected inductor  will increase to 4.8A. If you continue to want Iout to exceed 3A, theoretically the Isat will be greater than or equal to 5.5A as you wish, but this is not permitted in Webench design.

    B R 

    Colin