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CSD19532KTT: Thermal Resistance

tateo yamashiro
Guru 10890 points
Part Number: CSD19532KTT
Other Parts Discussed in Thread: CSD19532Q5B

Hi,

We got a question from the customer about CSD19532KTT.
Could you help us?

[Question]
They compared the thermal resistance between CSD19532KTT and CSD19532Q5B. They wonder why Rja of CSD19532KTT is bigger than CSD19532Q5B but Rjc of CSD19532KTT is smaller than CSD19532Q5B. D2PAK is bigger PKG than SON, therefore they assume the thermal resistance of CSD19532KTT will become smaller than CSD19532Q5B. Could you provide the reasonable reason why Rja of CSD19532KTT is bigger than CSD19532Q5B?

CSD19532KTT

CSD19532Q5B

Best Regards,
tateo

  • 0
    TI__Mastermind 30875 points
    Hello Yamashiro san,
    Thanks for the excellent question. Rtheta(j-a) for D2PAK is usually measured in free air like a TO220 and the industry standard value in datasheets from TI and competitors is 62degC/W. I checked datasheets from other vendors and some include Rtheta(j-a) = 40 degC/W when the D2PAK is PCB mounted on a 1 sq. in. copper pad. This should be a good number to use for the CSD19532KTT when it is PCB mounted on 1 sq. in. copper pad.