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CSD95372BQ5M: thermal questions

Bonnie Chen
Intellectual 1160 points
Part Number: CSD95372BQ5M

Hi Team,

can you help below for customer?

 

CSD95372BQ5M

1.Tcase maximum tolerance temperature?

2.Psijt Thermal resistance spec?

  • 0 in reply to Bonnie Chen
    TI__Mastermind 18200 points

    Bonnie,
    Thanks for posting. Is this question related to this other E2E post that just came in?

    https://e2e.ti.com/support/power_management/power_stage/f/208/p/684726/2524581#2524581

    If so, I believe the Psijt Thermal spec is what we would consider the thermal impedance through the top of the package right? If so, believe that is provided in the datasheet.

    What do you mean by Tcase maximum tolerance? We generally don't provide a temperature tolerance, but we advise staying under the max temperature in the recommended operating conditions (Tcase = 125 deg). However, we absolutely insist never exceed the abs max temperature 150deg.

    Did this answer your question? If not let me know, or it might be easier to take this up via email where I can loop in some other experts.

  • 0 in reply to Brett Barr1
    HI
    I'm George in charge of thermal design from Accton in TW.
    Thanks for your response.
    But the datasheet only shows the Rjc. No PsiJT is shown in datasheet.
    Rjc is not equal to PsiJT. It is more reasonal and accurate to use PsiJT to calculate Junction temperature.
    Could you pls check if the PsiJT can be provided to me?

    If you don't have the PsiJT number, you can provide me the max allowable case temperature (top surface temperature of chip) to be criteria.
    Then I can know if the measured temperature by thermal couple is over case temperature criteria spec.
    Now you show me the Tcase = 125 deg and does it mean the case temperature (top surface temperature of chip) is 125 deg?

    I need the information urgently
    thanks
  • 0 in reply to George Chang

    HI Brett

    Does any update?

  • 0 in reply to Brett Barr1
    HI Brett
    I'm George in charge of thermal design from Accton in TW.
    Thanks for your response.
    But the datasheet only shows the Rjc. No PsiJT is shown in datasheet.
    Rjc is not equal to PsiJT. It is more reasonal and accurate to use PsiJT to calculate Junction temperature.
    Could you pls check if the PsiJT can be provided to me?

    If you don't have the PsiJT number, you can provide me the max allowable case temperature (top surface temperature of chip) to be criteria.
    Then I can know if the measured temperature by thermal couple is over case temperature criteria spec.
    Now you show me the Tcase = 125 deg and does it mean the case temperature (top surface temperature of chip) is 125 deg?

    I need the information urgently
    thanks
  • 0 in reply to George Chang
    TI__Mastermind 18200 points
    George,
    I spoke with our packaging engineers about this at great length.

    We have had trouble measuring Psi JT with a great degree of precision, but have simulations that show it could be as low as <0.5deg C / W. Attempted measurements have shown it to be a bit higher, so we think somewhere in the 1-2deg C / W is more realistic. If you use 2 deg C / W, you are probably erring on the conservative side. This would imply that if you are dissipating ~3W of power, as long as the case temperature is < ~6 deg under Tjmax, you should be safe.