• State
  • Locked Locked
  • Replies 5 replies
  • Subscribers 47 subscribers
  • Views 3018 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

OPA549 Case Temperature

Clay Pearson
Prodigy 30 points
Other Parts Discussed in Thread: OPA549

I want to infer the the junction temperature of an OPA549 from the part's case temperature (Tj=Tc+theta_jc*Pd).  At which location on the package should I place the temperature probe?

  • 0
    TI__Mastermind 22297 points

    The tab is connected directly to the substrate.  This is the best  point for getting an approximate junction temperatuer measurement.

    Best regards,

    Art

  • 0 in reply to Art Kay
    Prodigy 30 points

    Thank you for your quick response.

    Is there an optimal point on the tab at which the case temperature should be measured?  If the optimal point is on the back side (the side against the heat sink) of the part, what's the best point on the front side?

  • 0 in reply to Clay Pearson
    TI__Mastermind 22297 points

    The temperature throughout the tab is fairly constant.  The measurement error will not be from temperature gradients in the tab, but from heat loss on the side of the temperature probe that is not against the tab.  Ideally the probe would be inside the tab; but this is obviously not practical.  I think if you place the probe under the tab, you will get the best results because you will not have the air current loss that you would have if you mounted above the tab.  I think the choice of thermal probe is important.  Choose something small and thin that can be mounted between the heat sink and tab and still allow a good mechanical (thermal) between the two.

  • 0 in reply to Clay Pearson
    TI__Mastermind 22297 points

    The temperature throughout the tab is fairly constant.  The measurement error will not be from temperature gradients in the tab, but from heat loss on the side of the temperature probe that is not against the tab.  Ideally the probe would be inside the tab; but this is obviously not practical.  I think if you place the probe under the tab, you will get the best results because you will not have the air current loss that you would have if you mounted above the tab.  I think the choice of thermal probe is important.  Choose something small and thin that can be mounted between the heat sink and tab and still allow a good mechanical (thermal) between the two.

  • 0 in reply to Art Kay
    Prodigy 30 points

    OK, thanks for your help.

    -Clay