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CSD17576Q5B: Understanding Junction temperature calculation

Jonathan Geronga
Expert 7930 points
Part Number: CSD17576Q5B

Hi Team,

I would like to get some assistance with our customer inquiry regarding the Maximum Junction temperature of CSD17576Q5B.
The customer is referring to page 7 of SPRA953C (https://www.ti.com/lit/an/spra953c/spra953c.pdf) with this formulat: (Tj=Tx+(RθJC x Power).

According to the customer, MOSFEt is rated at 30 Volts and 30 Amps, Power 900 W and which makes the Temperature 1170 degrees C
What's the relationship between the specification sheet and formula?

Additional question from the customer:
Is there a way to determine the number of cycles the MOSFET will perform before failure?

Please let me know if you have any questions with the customer.

Thanks!

Jonathan

  • 0
    TI__Mastermind 31645 points

    Hi Jonathan,

    Thanks for promoting TI FETs at your customers. First, I would like to point you to the MOSFET Support & training page at the link below. This is where all of the MOSFET technical information is located including a blog series on understanding MOSFET datasheets. I have included links to two of blog entries on continuous current ratings and thermal impedance. Lastly, you will find a link to a technical article on how much power can be dissipated in our FET packages. These are "rule of thumb" estimates based package thermal impedance and empirical data. Please review this information.

    No MOSFET can dissipate 900W. The MOSFET voltage rating or BVDSS is based on the process technology and is the maximum voltage the FET can sustain without experiencing avalanche breakdown. The current rating of the MOSFET is a calculated value based on thermal impedance, maximum junction temperature and on resistance as explained in the blog. Information on reliability including DPPM/FIT/MTBF estimator is available TI.com by clicking on Quality & reliability. I am including a link below. I am going to close this thread. If you have additional questions, please contact me on my TI.com email.

  • 0 in reply to John Wallace1
    TI__Expert 7930 points

    Hi John,

    Thank you for this information.

    I will share this with our customer and let you know once there are other questions.

    Regards,

    Jonathan

  • 0 in reply to Jonathan Geronga
    TI__Mastermind 31645 points

    Hi Jonathan,

    I am going to close out this thread. Please reach out to me on regular email if there are additional questions.