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LM5122-Q1: LM5122

John Man
Prodigy 20 points
Part Number: LM5122-Q1
Other Parts Discussed in Thread: LM5122

Dear Sirs,

I am currently designing a boost circuitry by using LM5122QMH/NOPB. Firstly, I use Web bench to look at the result. The Web bench result shows that M1 pd is 2.908W(at Vin=8V;Iout=7A)  and Rthia of M1 mosfet is 57degC/W per its datasheet, the ambient temperature is 30 degC. The junction temperature calculated is 2.908*57+30=195.756 degC. However, the M1 Tj curve in the web bench report shows 110 degC.

Can you help to explain how this 110 degC come from? Is this 110degC measured on a real PCBA board?lm5122-q1.pdfWBDesign63.pdf

Thanks

John

  • 0
    TI__Genius 11335 points

    Hi John,

    Rthja is a parameter that is strongly ralated to the cooling method, PCB layout. Please take a look at note1,2 of Rthja which identifies the cooling condition. You may reduce Rthja by using larger copper pad or fan cooling.

    Best Regards,

    Feng Ji