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DP83848K temp specs

Aaron Spaete
Expert 4527 points
Other Parts Discussed in Thread: DP83848K

Team,

Can you tell me what the maximum recommended operating temperature of this device is? I only see the maximum recommended ambient temperature (85C) and the absolute maximum junction temperature (150C) spec'd in the datasheet. A maximum recommended case temperature would be fine, too.

Thanks,

Aaron

  • 0
    TI__Mastermind 31600 points

    Aaron,

    Since the case and junction temperatures can change based on configuration and application, we provide data for calculating the values instead of providing the values themselves.  We have an application note with details on the power consumption of the DP83848 for various conditions (http://www.ti.com/lit/pdf/snla089). 

    Using the application note and the data in the datasheet, below are example calculations based on:

    • 100 Base-Tx Operating Mode Power (3.3V, 25C, 787 byte packets of incrementing bytes):  294.65mW
    • Maximum Ambient Temperature:  85C
    • Theta Junction to Case (Tjc):  8.8 C/W
    • Theta Junction to Ambient (Tja), no airflow:  31.7 C/W

    Junction Temperature:  85C + (31.7 C/W * 0.29465W) = 94.34C

    Case Temperature:  94.34C - (8.8 C/W * 0.29465W) = 91.75C

    Patrick

  • 0 in reply to Patrick OFarrell
    TI__Expert 7055 points

    Patrick,

    Thanks for the quick answer.   From the application note, should we make the assumption that the highest power configuration for the DP83848K determines the maximum recommended junction temperature?

    From the example above, it seems the recommended junction temperature is 94degC.  Using the worst case I found in the application note, I get 341mW ==> 95.8degC.

    If we have a better heat sink, but higher ambient (for example) Is 100C (at the junction) safe? 110C?

    Thanks for the help!

    Jake

  • 0 in reply to Jake Salmi
    TI__Mastermind 31600 points

    Jake,

    I would position it this way.  We can tolerate the maximum normal operating power at the highest ambient temperature with some margin.  Increasing the junction temperature beyond that will eventually result in spec failures.

    If the ambient temperature for this application is higher than 85C, we have other devices in the portfolio that are rated to 105C or even 125C.  Choosing one of those devices might be easier than adding a heat sink to the DP83848K.

    Patrick