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TPS65987D:What limits the operating ambient temperature?

user1866475
Intellectual 350 points
Part Number: TPS65987D
Other Parts Discussed in Thread: TPS65988

Hi all,

Our board with your TPS65987D mounted reaches 90°C. In datasheet, the ambient temperature limit is 75°CMax while the junction temperature limit is 125°CMax.

This is too low for the junction temperature. Are other factors besides the junction temperature limiting it?

The RJA of the TPS65987D is 57.7 K/W, but the current consumption of the device is 8mA and the PPHVx power switch is 33 mohm Max, so even at 3 A it is 0.3W. If the ambient temperature is governed solely by the junction temperature, then I would think it could be set much higher.

https://e2e.ti.com/support/interface-group/interface/f/interface-forum/966960/tps65987d-ta-and-tj?tisearch=e2e-sitesearch&keymatch=TPS65987D%2520temperature#

I would have preferred to expand the operating ambient temperature, but I knew that was not possible. I checked other cases and recognized that there are no industrial grade products that are compatible with PD3.0.

Can I expand the operating ambient temperature in my use case with justification?

Or can you suggest a PD3.0 controller for higher temperatures?
We supply 45W as power source device, power sink is not supported. Data communication is supported at super speed 5GHz as host.

Best Regards,

Yukio Oyama

  • 0
    TI__Mastermind 32280 points

    Hi,

    Can I what environment the product is used in?

    TPS65987D reaching 90°C when only sourcing 45W seems weird.

    On our USB-C-PD-DUO-EVM that also uses TPS65987D it did not reach near 90°C when sourcing 100W.

    It seems like there are layout issue that the heat is not dissipating correctly.

    Regards

  • 0 in reply to Tommy Lin
    Intellectual 350 points

    Hi Tommy-san,

    I am not saying that TPS65987D supplying 45W will get to 90°C. PCBs are hotter due to other heat sources. This means that regardless of the operation of the TPS65987D, the operating environment is already 90°C.

    And I am asking about the upper operating temperature limit of the TPS65987D being too low relative to the upper junction temperature limit.

    And the RJA of TPS65987D is 57.7 K/W while the RJA of TPS65988 is 36.4 K/W(see 6.4 Thermal Information in the datasheet). Different values in the same package and on the same board in the same package is odd. The number of VBUS paths has nothing to do with this parameter.

    Best Regards,

    Yukio Oyama

  • 0 in reply to user1866475
    TI__Mastermind 32280 points

    Hi,

    Let me reach out to systems engineer regarding these question. I will get back to you by Thursday EOB.

    Regards

  • +1 in reply to Tommy Lin
    TI__Mastermind 32280 points

    Hi,

    The RJA difference in TPS65987D and TPS65988 is the result in number of switches/power path available for heat dissipation. TPS65987D always assume there are only one switch in on for heat dissipation while TPS65988 assume there are 2 switches available for heat dissipation.

    There should be no problem regarding the temperature as long as the junction temperature of TPS65987D don't hit 125°C.

    Regards

  • 0 in reply to Tommy Lin
    Intellectual 350 points

    Hi,

    Based on your answer, if I were to imagine the mechanism, I would assume that the power path would take up much of the die area of the chip, is that correct? If not, please explain why the number of power paths affects the RJA.

    Is my understanding correct that if the die junction temperature does not hit 125°C, then there is no problem for device action.
    If the power consumption of this IC is about 0.3W, is it ok if the package temperature is less than 114°C? Because psiJT(top) is 34.1°C/W, Die temperature do not reach 125°C if package temperature is below 114°C.

       Package top temperature : 125°C - (34.1°C/W x 0.3234W) = 113.97°C

          Power Path loss: 33mohm x 3A  x3A  = 0.297W

          IC consumption : 3.3V x 8mA = 0.0264W

    Best Regards,

    Yukio Oyama

  • 0 in reply to user1866475
    TI__Mastermind 32280 points

    Hi,

    I cannot reveal information regarding the die area but yes you are somewhat correct on that.

    For the calculation part that seems right to me.

    Regards

  • 0 in reply to Tommy Lin
    Intellectual 350 points

    Hi,

    Thanks for your support and confirmation, thank you.
    I will close this case.

    Best Regards,

    Yukio Oyama