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LP38512-ADJ: Theta_JA of LP38512-ADJ(SO) and TPS7A90

Genius 15550 points
Part Number: LP38512-ADJ
Other Parts Discussed in Thread: TPS7A90, LP38512

Hello,

 
I wants to use TPS7A90 or LP38512-ADJ(SO package) for a project.
And I want to select the device which has better thermal performance.
Then I compared Theta_JA of both devices.
Theta_JA of LP38512-adj(SO) is 168 C/W while TPS7A90 is 56.9 C/W.

Are both Theta_JA parameters specified under the same condition?

I think Theta_JA is JEDEC standard and it should be under the same condition to be able to compare the package thermal performance.
But I feel LP38512-adj(SO)’s Theta_JA, 168 C/W, is too high although it has power pad. 

Regards,
Oba

 

  • Hi Oba,

    The Theta_JA number listed in PDS for LP38512 seems higher to me as well. But if you look closely in the rest of the datasheet, this is not done with JDEC standard. The datasheet does have a few other plots that show the change of Theta_JA with different thermal via counts(Figure 23) and different copper area (Figure 25). With proper layout and consideration for the thermals, you could get much better Theta_JA number with the SO powerpad package for LP38512. 

    The Theta_JA number for TPS7A90 is using JEDEC standard as most of our other LDOs are.

    Regards,
    Jason Song