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LMH6642: temp capability

Aaron Spaete
Expert 4537 points
Part Number: LMH6642


Team,

My customer has the following question.   I believe we are OK since Tj is 150C, but customer wants to verify.  

I need some clarification on the maximum temperature capability of the LMH6642MA/NOPB.

I have an application where the device is dissipating 25mW on a board that is 88.7C. The junction temperature should be Tj = 88.7C 0.025W x 190C/W = 93.5C.

Is this below the temperature that will cause damage to this part?

Regards,

Aaron

  • 0
    TI__Genius 15975 points

    Hi Aaron,

    The customer's operation of LMH6642 at 88.7'C ambient temperature should be ok, and will not cause damage to this part. However, it might be good to check the junction temperature when the device is sourcing/sinking current at the output with 88.7'C Ta, or in terms of dynamic power dissipation. I believe the dynamic power dissipation is more critical for this part because of its +/-75mA load current drive capability.

    Do you know what is the output swing and load resistance being driven by the LMH6642 output?

    Best Regards,

    Rohit

  • 0
    TI__Expert 8650 points
    Hi Aaron,

    Yes that should be fine. To be honest, your ambient temperature is probably quite a bit lower than your board temperature so you would likely have even more headroom since the 190 degree value is for junction to ambient.

    Regards,
  • 0
    Prodigy 100 points

    I am the customer on this one.  The LMH6642 is used as  a buffer to an ADC sampled at 4MHz.  The typical voltage swing is less than 100mV.  

    The board is tightly sandwiched between an aluminum  chassis and cover with no air flow.  The temperature from aluminum to board to air is the same .

    Do these added details make any difference?

  • 0 in reply to Travis Christle
    TI__Genius 15975 points

    Hi Travis,

    I think you should be ok with the LMH6642 design without having the thermal issues.

    Best Regards,

    Rohit