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TPS65988: thermal information

K.Yaita
Guru 29720 points
Part Number: TPS65988
Other Parts Discussed in Thread: TPS65987D

Hi Team,

There is large difference between thermal parameter of TPS65987D and TPS65988 as the following.
Is it true?
For example, ψjt of TPS65987D is 3 times larger than TPS65988.
I believe these devices are same package..

- TPS65987D


-TPS65988


Best Regards,
Yaita

  • 0
    TI__Mastermind 36756 points

    Hi Yaita-san,

    I will check with the lead systems engineer for this part. I should have an answer for you by tomorrow at the latest.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    TI__Mastermind 36756 points

    Hi Yaita-san,

    The thermal simulations were done using the layout from the TPS65988EVM for both the 987D and 988. For the 987D, only one of the internal power paths (and one VCONN path) was used and 5A of current were simulated on that power path. For the 988, both of the power paths were simulated with 3A across each (and both VCONN paths).

    The test case was different for both devices so it is difficult to compare the two. I hope this helps.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Guru 29720 points

    Hi Eric-san,

    Thank you for your support.
    Do you refer it is difficult to estimate TJ from TC by the following equation?

    TJ = TC + ( ψjt x Power)
    *The following application note shows the equation above in page 8.
     http://www.ti.com/lit/an/spra953c/spra953c.pdf

    My customer concerned if it is reasonable to estimate TJ from ψjt because ψjt is so large value in TPS65987D.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 36756 points

    Hi Yaita-san,

    The values for the Thermal Information are all simulated using the TPS65988EVM layout. There is no estimation for these values. They are all directly from the thermal simulations. Please note that the test case for the TPS65987D is different than the test case for the TPS65988. The TPS65987D has 5A of current going through one of the power paths. That means that the source of heat is much more centralized to one of the power paths. In the TPS65988 simulation, there is 3A of current going through both power paths simultaneously. This means that the source of the heat is dispersed, hence the difference in thermal results between the two devices.

    Thank you,
    Eric

  • 0 in reply to Eric Beljaars
    Guru 29720 points

    Hi Eric-san,

    Thank you for your support. I understand test case is different between TPS65987D and TPS65988.

    In general, I understand TJ (junction temperature) can be estimated from ψjt as the following equation.
    --------------------------------------------------
    TJ = TC + ( ψjt x Power)
    *The following application note shows the equation above in page 8.
     www.ti.com/.../spra953c.pdf
    --------------------------------------------------
    My customer concerned if it is reasonable to estimate TJ from ψjt of TPS65987D because ψjt is so large value.
    What do you think of it?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 36756 points

    Hi Yaita-san,

    I think it is still reasonable to estimate TJ from ψjt for TPS65987D. Keep in mind that these test cases will result in the worst-case scenario for thermal information. If they will just pass 3A through the TPS65987D, then they can use the ψjt value from the TPS65988 for their calculations.

    Thank you,
    Eric