WEBENCH® Tools/TPS549D22: Thermal Simulation of IC-Die is lower than IC-TOP

user1874945

Part Number: TPS549D22
Other Parts Discussed in Thread: TPS549B22, TPS548B22

Tool/software: WEBENCH® Design Tools

Hi TI Expert,

I'm using TI Webench to do some thermal simulation. Vin=12V, Vout=3.3V, Iout=23.5A, TI converter=TPS549D22

Per the simulation result, the IC Die temperature is lower than IC -TOP. It seems unreasonable. Suppose IC Die is the hottest spot. Could you help to explain the reason?

The Webench link is as below.

webench.ti.com/.../webench5.cgi

Thanks,

Dora

over 7 years ago

0 JohnTucker over 7 years ago

TI__Guru**** 191445 points

Dora,

We have someone looking into this.

0 JohnTucker over 7 years ago in reply to JohnTucker

TI__Guru**** 191445 points

Dora,
The values ideally should be very close but we have seen variations as much as 15-20C in some cases and this difference is due to the way the opval and WebTHERM models calculate the temperature. I have reviewed the comparison results for the TPS549B22 as an example and they look quite good at least for the EVM. We are working on locating the TPS548B22 data as well.

0 user1874945 over 7 years ago in reply to JohnTucker

Intellectual 300 points

Hi John,

Should IC Die temperature be higher than IC -TOP in all circumstance? Does IC Die in Webench mean junction temperature?

Thanks,
Dora

0 JohnTucker over 7 years ago in reply to user1874945

TI__Guru**** 191445 points

Dora,

Ideally, the IC die temperature (same as the Tj or junction temperature) should be higher than the top case temperature in every case. The difference may be due to the calculation method which may be off by 15 to 20 degrees. That variance is large compared to the slight difference between Tj and Tcase top. We are still looking into the fine details. We have only verified one (the EVM) condition. Just keeping you posted on the progress.

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WEBENCH® Tools/TPS549D22: Thermal Simulation of IC-Die is lower than IC-TOP