Thermal analysis parameters for LM2674

Mike Oliva71

Other Parts Discussed in Thread: LM2674

Where can I get the thermal analysis parameters for the LM2674 (Psi-JT et al.)? And just for my curiosity, why is the information so hard to find?

Thanks!

over 9 years ago

0 Anston Lobo over 9 years ago

TI__Genius 16025 points

Hi Mike,

Sorry for the trouble. What package type are you using? Hopefully this document answers your question:
www.ti.com/.../snoa401r.pdf

Let me know if it doesn't and we'll get you what you're looking for.

PS: Webench does a good job simulating Thermal data too.

Thanks,
Anston

0 Mike Oliva71 over 9 years ago in reply to Anston Lobo

Prodigy 50 points

Sorry! I should have stated which package. SOIC-8.

Thanks again!

0 Mike Oliva71 over 9 years ago in reply to Anston Lobo

Prodigy 50 points

Do you have any information yet for the SOIC-8 package?

Thanks!

Mike

0 Anston Lobo over 9 years ago in reply to Mike Oliva71

TI__Genius 16025 points

Hi Mike,

Yes. I received this information today. I needed to put in a request for it.

Theta JA-High K (standard datasheet value) 110.7
Theta JC, top (standard datasheet value) 54.7
Theta JB (standard datasheet value) 51.3

Psi JT (standard datasheet value) 9.2
Psi JB (standard datasheet value) 50.7

The Psi values will be more accurate than the Theta values by virtue of what they represent. These measurements were taken using the same package but a slightly smaller die, hence these values are already a little higher than what you might actually see.

Thanks,
Anston

0 Mike Oliva71 over 9 years ago in reply to Anston Lobo

Prodigy 50 points

Thank you Anston!!

0 Mike Oliva71 over 8 years ago in reply to Mike Oliva71

Prodigy 50 points

During an internal design review, I discovered that another engineer requested this same data and he received an email from TI stating that the Psi JT is 4.6. The data I received via this forum is Psi JT = 9.2 (exactly twice the other value). Can you verify which number we should be using for the SOIC-8 package (I believe the datasheet refers to it as the D Pkg)? I also recall that you mentioned that the 9.2 value came from a part with a smaller die and might be pessimistic. Could that be the reason for the discrepancy?

Thanks!

Mike

0 Anston Lobo over 8 years ago in reply to Mike Oliva71

TI__Genius 16025 points

Yes! The smaller die can affect this value and make it larger than it should be. If you have tolerance to play with, I would suggest using the worse of the two values.

Thanks,
Anston

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Thermal analysis parameters for LM2674