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CSD18537NQ5A: Thermal resistance & Thermal characterization parameter

Hong Jieun
Prodigy 240 points
Part Number: CSD18537NQ5A

Hi I'm Jieun, 

I have a question about thermal information of CSD18537NQ5A. 

I'd like to know case(top) temperature spec by measuring top temperature and calculating with below equation.

Tc = Tj (150℃) - ψjt(℃/W) * W

That is why I need the junction-to-top characterization parameter.

But, in datasheet, there is only Junction-to-case Thermal resistance. 

1) Please let me know the junction-to-top characterization parameter. 

2) Or, Is it okay to use Junction-to-case Thermal resistance?

     2-1) If yes, could you let me know the reason?

best regards,

  • 0
    TI__Mastermind 29535 points

    Hello Jieun,

    Thanks for your interest in TI FETs. TI does not provide thermal characterization parameters for our FETs. We only spec RθJA and RθJC in Table 5.2 in the datasheet for the pad and board sizes shown below the table. The value for RθJC is to the thermal pad (drain) on the bottom of the package. The estimated value of RθJC to the top of the package for the CSD18537NQ5A is 35°C/W. Please see the blog at the link below for more information on how TI tests and specs thermal resistance for our FETs. Let me know if you have any additional questions.

    http://e2e.ti.com/blogs_/b/powerhouse/archive/2016/06/10/understanding-mosfet-data-sheets-part-6-thermal-impedance

    Best Regards,

    John Wallace

    TI FET Applications

  • 0 in reply to John Wallace1
    Prodigy 240 points

    Hi John, 

    Thanks for replying, 

     

    Is there any special reason why TI doesn't provide thermal characterization parameter(ψ) for FETs?

    why does TI provide only RθJA and RθJC for FETs?

     

    And how could you estimate RθJC to the top of the package for the CSD18537NQ5A as 35°C/W?

    I'm looking forward to getting your reply.

    Best Regards,

  • 0 in reply to Hong Jieun
    TI__Mastermind 29535 points

    Hi Jieun,

    I do not know the reason TI has never provided thermal characterization parameters for our FETs. As far as I know, most MOSFET vendors do not provide thermal characterization parameters  The estimated RθJC top is based on thermal simulations done many years ago when the part was released to production. Can you use RθJC top and bottom for your design?

    Thanks,

    John

  • +1 in reply to John Wallace1
    Prodigy 240 points

    Hi John, 

    Thanks for reply, 

    Let me know how could you estimate the RθJC top value as 35°C/W?

    Is it calculated value ? 

    Best Regards, 

  • +1 in reply to Hong Jieun
    TI__Mastermind 29535 points

    Hi Jieun,

    Please see my previous response. The estimated value of RθJC top is based on thermal simulations done several years ago when the product was first released to manufacturing. Please let me know if you have any additional questions.

    Thanks,

    John