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Webench IC ThetaJA Effective

K. Sasaki14
Guru 10200 points
Other Parts Discussed in Thread: TPS56C215

I would like to ask about "IC thetaJA Effective".
What does this mean? And how do you calculate this value?

This value is a little lower than ThetaJA value in datasheet. I think there was the ThetaJA value of datasheet on WEBENCH in the past.
Is this added function these days?
I found this value in TPS56C215 simulation.

Best Regards,
Kohei Sasazki

  • 0
    TI__Genius 17905 points
    Hi,

    Thermal performance is highly dependent on PCB layout. The ThetaJA value listed in datasheets is based on JEDEC standard test boards and ThetaJA values derived from these JEDEC boards are usually higher and more conservative than the ThetaJA on real application board layouts.

    For low current devices with relatively low internal power dissipation (less than 1-2W), using the datasheet ThetaJA value gives reasonable junction temperature estimations (IC Tj = Ta + Pdiss * ThetaJA), and that worked well in the past. However, in the past few years, as we have integrated higher current integrated FET power devices into WEBENCH(R) Designer, we needed a way to represent a more realistic application board ThetaJA to the user. That is what we intend with the "IC ThetaJA Effective" value. For devices we include in WEBENCH Power Designer, we get efficiency (power dissipation) and thermal measurements on each device's evaluation board (EVM) and calibrate an 'effective' ThetaJA on this application board to try to give more realistic thermal performance results to the user in the WEBENCH interface.

    I hope this clarifies what this value means. Please let us know if you have any other questions, and thanks for looking at TI products.

    Regards,
    Kris