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LMR51435: Difference in θj-c between the LMR51435SDRRR and the MAX42403AFLB+

Shinichi Inoue
Guru 21841 points
Part Number: LMR51435


Tool/software:

Dear Specialists,

I am proposing the "LMR51435SDRRR" to a customer as a replacement for the MAX42403AFLB+.

The customer has a question about thermal resistance.

I would be grateful if you could advise.

---

The θj-a is 47.4°C, which is better than the ADI product. That's a good point.

The LMR51435 has θj-c(top)=44.6°C, while the MAX42403AFLB (ADI) has θj-c=21°C, so there is a difference.

I am concerned about the difference.

What is causing this difference? (Is there a difference in measurement conditions?)

Why are the θj-c values ​​different even though the θj-a values ​​are almost the same?

---

I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Guru 74055 points

    Hello

    It is best to compare, and/or decide, thermal performance based on the effective thetaJA of the device on a PCB.

    The LMR51435 has an effective thetaJA of 23°C/W when mounted on the EVM.

    The thetaJC(bott) is 6.3°C/W.

    The thetaJC(top) is used if a heatsink is used on the top of the package.

    Thanks

  • 0 in reply to Frank De Stasi
    Guru 21841 points

    Hi Frank,

    Thank you for your reply.

    I understand.

    I'll share your suggestion with the customer.

    When the customer has an additional question, I consult you again.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi