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LM5158: Bug in WEBENCH?

Axel Huelsmann
Prodigy 10 points
Part Number: LM5158

Tool/software:

WEBENCH selects a transformer VP2-0066R from Eaton, but calculates the wrong series resistances.

I entered the following data to WEBENCH:

VinMin = 16.0V

VinMax = 32.0V

Vout = 4.0V

Iout = 1.5A

Device = LM5158RTER

Topology = Flyback

The VP2 transformers have 6 coils, which aer connected to result in:

Lp= 12.8 µH, Rp= 90.0 mOhm, Leakage_L= 166.0 nH, Ns1toNp= 500.0 m, Rs1= 90.0 mOhms, Ns2toNp= 1.0, Rs2= 180.0 mOhms

As Lp is acheived by connecting two coils in series Rp should be 180mOhm and Rs2 should be 90 mOhm to my understanding.

Did I undertssna dsomething wrong, or is there a bug in WEBENCH?

  • 0
    TI__Genius 15855 points

    Hi Axel,

    Thanks for using E2E.

    Can you please send me your webench design? When i enter your specs in webench, it will not recommend VP2-0066R from Eaton to me.

    Also from the datasheet i see that 1 winding has 3.2uH. So it would need 4 of them in series to achieve 12.8uH.

    Best regards,

    Moritz