TPSM84338: Thermal metric

Charles Zhang1

Part Number: TPSM84338

Hi Team,

May I know the reason why junction to case thermal resistance of TPSM84338 is higher than its junction to ambient thermal resistance?

In general, Rtheta_JC should be lower than Rtheta_JA.

TPSM84338_thermal metric.png

23 days ago

0 Haseen Reddy Siripi Reddy 23 days ago

TI__Genius 9670 points

Hi Charles,

We will check and get back on this.

Regards,

Haseen.

0 Haseen Reddy Siripi Reddy 22 days ago in reply to Haseen Reddy Siripi Reddy

TI__Genius 9670 points

Hi Charles,

Theta-JA and Theta-JC are completely separate tests so it is possible for Theta-JC to be higher.

Theta-JC is designed for characterization of the top side cooling thermal performance of the package so it places a heat sink on top of the package and allows minimal cooling through the board. In the Theta-JA test the device is primarily cooled through the board.

Regards,

Haseen.

0 Charles Zhang1 3 days ago in reply to Haseen Reddy Siripi Reddy

TI__Expert 3450 points

Hi Haseen,

Thanks for your comment.

I have one follow-up question here, to estimate the junction temperature, do you have any recommended approach?

In general, my customer will probe the temperature of top side case to get Tc, and use the equation Tc + P_diss * RthetaJC = Tj to get the junction temperature.

I am not sure if this approach is accurate, the Rtheta JC of TPSM84338 is 58.1C/W, which is pretty high.

Regards,

Charles

0 Haseen Reddy Siripi Reddy 2 days ago in reply to Charles Zhang1

TI__Genius 9670 points

Hi Charles,

Yes this approach is fine "In general, my customer will probe the temperature of top side case to get Tc, and use the equation Tc + P_diss * RthetaJC = Tj to get the junction temperature."

Regards,

Haseen.

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TPSM84338: Thermal metric