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WEBENCH® Tools/LM5145: High side and Low Side MOSFET Junction Temperature calculation Error?

Ashwin S1
Prodigy 90 points
Part Number: LM5145

Tool/software: WEBENCH® Design Tools

Hi,

I have attached the TI webench result for the LM5145 Switcher. In that when I am changing the input voltage range to 40-60V, M1 and M2 junction temperature are within range. But when i changed to 10-60V M1 Tj 121.649 degC and M2 Tj 194.038 degC, M2 range is above the maximum junction temperature. Please advise whether we can proceed further. 

Thanks and Regards,

Ashwin S

WBDesign7_Steady State-5.pdf

  • 0
    TI__Mastermind 30435 points

    Hi Ashwin,

    let me check and update you later.

    B R

    Andy

  • 0
    TI__Mastermind 30435 points

    Hi Ashwin,

    Sorry for the late!

    The M2 has 11mohm RDS(on), it may increase to 20 m ohm at high temp 150C, 

    the conduction loss Pd is  20m*12*12=2.88W at 60Vin, the switching loss M2pdsw is only 0.21W per Webench simulation 

    So you need use MOSFET with even lower RDS(on) <6mohm for M2.

    You can check the MOSFET P/N used by Webench for  input 40V--60V to output 3.3V/12A, and use same one for 10V--60V input conversion.

    B R

    Andy