CSD18536KTT: Where is definition of case top of RθJC

Hideki Hayashi1

Expert 8400 points

Part Number: CSD18536KTT

Hi team,

Can you please let me know where is definition of case top of RθJC? Is it the center of thermal pad(drain)?

If yes, customer can't measure "case top" temperature. Can customer measure thermal pad's top as Tc?

Best regards,

Hayashi

over 1 year ago

0 John Wallace1 over 1 year ago

TI__Mastermind 38390 points

Hello Hayashi-san,

Thanks for the inquiry. The junction-to-case thermal resistance, RθJC specified in the datasheet is to the bottom of the tab as shown in the lower figure of the drawing you included. TI does not spec RθJC to the top of the package. Based on earlier simulations, RθJC to the center of the plastic package on top is approximately 30°C/W. Measuring on the metal tab on top should be much lower as the FET die is mounted directly on the metal tab. Please let me know if you have questions or need additional information.

Best Regards,

John Wallace

TI FET Applications

0 Hideki Hayashi1 over 1 year ago in reply to John Wallace1

TI__Expert 8400 points

Hi John

Thank you. Let me confirm. On the below picture, is the red circle is defined as RθJC? Also, if the customer measures temp of the blue circle, its themarl metric will be over RθJC and lower 30C/W, correct? Have you specified this thermal metric?

Regards,

Hayashi

0 John Wallace1 over 1 year ago in reply to Hideki Hayashi1

TI__Mastermind 38390 points

Hi Hayashi,

I believe the RθJC (bottom) measurement is made near the center of the tab on the bottom of the package but I will have to confirm with a colleague as I was not involved with the actual testing. This will have to wait until next week when he is back from the holidays. The temperature in the blue circle should not vary much from the temperature in the red circle on the bottom of the package is the tab is one continuous piece of metal on which the FET die is mounted. Please see the blog at the link below for more information on how TI tests and specs thermal impedance for our FETs. I will update you as soon as I have more information.

Best Regards,

John

http://e2e.ti.com/blogs_/b/powerhouse/archive/2016/06/10/understanding-mosfet-data-sheets-part-6-thermal-impedance

0 John Wallace1 over 1 year ago in reply to John Wallace1

TI__Mastermind 38390 points

Hello Hayashi,

Following to see if your issue has been resolved. Please let me know.

Thanks,

John

0 Hideki Hayashi1 over 1 year ago in reply to John Wallace1

TI__Expert 8400 points

Hi Johm,

John Wallace1 said:
I will have to confirm with a colleague as I was not involved with the actual testing. This will have to wait until next week when he is back from the holidays

I was waiting for the updates from your comment. But it will be good if the red circle and blue circle is similar in temperature point.

Best regards,

Hayashi

0 John Wallace1 over 1 year ago in reply to Hideki Hayashi1

TI__Mastermind 38390 points

Hi Hayashi,

Apologies for my confusion. I checked with a colleague and he was not certain but thought it was near the center of the tab. Unfortunately, The people who did the actual testing are no longer with TI.

Thanks,

John

Power management

Power management forum

CSD18536KTT: Where is definition of case top of RθJC