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Original question:

TPS82130: Thermal derating curve

TPS82130: Thermal dependency on efficiency

Taketo Sato
Genius 10325 points
Part Number: TPS82130

Hello team,

I have a question about thermal dependency on efficiency.

This is relating below post.

https://e2e.ti.com/support/power-management/f/196/p/880292/3256899

We can calculate power dissipation is about 1.08W by Ta=75C, 12Vin, 3.3V/2A out, Theta-JA value and Tj_max from the graph.

However, efficiency curve says efficiency is about 87.5% with 12Vin, 3.3V/2A out and we can calculate power dissipation is about 0.94W.

Does this mean there is big efficiency difference between Ta=25C and Ta=75C?

If yes, what contributes to the big difference? Inductor characteristics?

Best regards,

  • 0
    TI__Genius 17905 points

    Hi Sato-san,

    Elevated ambient temperature will typically lead to more power dissipation as FET Rdsons and inductor DCR will increase with temperature. Taking the power dissipation difference of 140mW and dividing by Iout^2, the DC resistance increase to account for the difference is only about 35mohm. I do not think this delta is unreasonable. Furthermore, these are typical curves in the datasheet as well, and the efficiency graph and SOA may not have been tested on the same unit so there could be some part-to-part variation in Rdson/DCR to factor.

    Regards,
    Kris