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TPS709 - thermal metrics for DBV and DRV packages

Jesse Dennis54
Prodigy 10 points
Other Parts Discussed in Thread: TPS709

The TPS709 datasheet provides Junction-to-board characterization parameters of 38.7 C/W for the DBV in SOT23-5 package, and 42.9 C/W for the DRV in WSON package. Normally I would expect the DRV WSON with exposed  thermal pad to have reduction of Junction-to-board thermal parameter. Is there an reason the DRV package is larger?

  • 0
    TI__Prodigy 115 points

    Hi Jesse - That's a very astute observation. My first inclination was the same as yours, but I think this is actually due to the amount of area being soldered down on the SOT23-5 is (surprisingly) still larger than the DRV package even though there is an exposed thermal pad. In the case of the SOT, the thermal resistance to the board is reduced by having good thermal conduction to the lead frames and significant area connected to the board at each pin. By the mechanical drawings in the back of the TPS709 datasheet; I read the following areas:

    SOT23-5: 1mm x 0.55mm x 5 pins = 2.75mm^2
    WSON DRV: 0.25mm x 0.3mm x 6 pins + 1mm x 1.6mm (thermal pad) = 2.05mm^2

    As you can see, the DRV has a smaller soldered down area in comparison to the SOT23-5.

    In the end, I would suggest taking a look at this document (www.ti.com/.../spra953b.pdf), which talks about more detail regarding the Junction-to-board measurements. In it you'll see that in practice, the actual resistance you'll see could vary quite a bit from what you see in this specification, so given the margin of error I would characterize the junction-to-board parameters between these two packages as being comparable.

    Regards,