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Original question:

θja of LM317M

LM317M: θja of LM317M

Aleksandr Morozov
Prodigy 120 points
Part Number: LM317M
Other Parts Discussed in Thread: TLV1117,

Hello, team!

Recently my customer has needed thermal information of LM317MKVURG3 KVU-package. The answer for this question was found here

After that the customer found some interesting details:

SOT-223 has ThetaJA=60,2 C/W

TO-252 has ThetaJA =56,9C/W,

As can be seen, the value is almost equal to each other.

By the way, the customer noticed that the value of same options of TLV1117 are different

On Semi's LM317M. The difference of value is even greater. (My customer knows that TI and OnSemi calculate this characteristic in different ways, so he compares the parameter within one manufacturer)

 


Tell me please, are the following data correct?

ThetaJA = 56.9 C/W
ThetaJC (top) = 36.1 C/W
ThetaJC (bottom) = 1.8 C/W
ThetaJB = 29.3 C/W
PsiJT = 3.8 C/W
PsiJB = 28.8 C/W

and, whether there is an error in the reply on the link above?

Thanks in advance!


  • 0
    TI__Guru 55940 points
    Hi Aleksandr,

    The data populated in each datasheet is correct for the datasheet given.

    For TLV1117 ThetaJA is 104.3 C/W for the DCY package and 50.9 C/W for the KVU package.

    For LM317M ThetaJA is 60.2 C/W for the DCY package and 56.9 C/W for the KVU package.

    There are a variety of factors that impact the thermal performance of a device including leadframe, die size, die placement/orientation in the package, mold compound, and more. While the type of package has a large impact on thermals, due to the other factors, there can still be a large variation between two devices in the same package.

    The Thermal Information table is populated with data modeled following JEDEC's EIA/JESD51-x series of documents. The TI interpretation of these measurements can be found in the following Application Report. As you stated, not all companies calculate these metrics the same way.

    www.ti.com/.../spra953c.pdf

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Expert 3560 points

    Hello Team,

    Can you also confirm thermal data for LM317MKTPR? One of my customer has requested for the same.

    Regards,

    Mahendra Patel

  • 0 in reply to Mahendra Patel1
    TI__Guru 55940 points
    Hi Mahendra,

    Unfortunately the KTP package is obsolete for the LM317M family. The thermal information does not appear to have been provided at anytime for the KTP package.

    Very Respectfully,
    Ryan