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Thermal performance of the TLV1117CKTTR (TO-263 package)

Christian Plourde
Prodigy 645 points
Other Parts Discussed in Thread: TLV1117, TPS74301

Hi everybody,

The datasheet of the TLV1117 provides the Theta-JA values for the different packages available. The TO-263 package (TLV1117CKTTR) has a DAP that helps dissipate the heat. This also means that the Theta-JA can be greatly reduced by enlarging the surface of the copper area underneath the component.

The datasheet suggests to use the thermal calculator tool to evaluate the impact of different copper areas. Unfortunately, the tool doesn't support the TO-263 version of the TLV1117 yet.

Here are the 2 questions from my customer:

The Theta-JA provided in the datasheet for the TLV1117CKTTR is 27,5 degrees/Watt.

1- What was the dimension (and thickness) of the copper used to obtain that value?

2- What would be the impact of enlarging the copper area? Do we have a curve or a table showing it?

All all these questions refer to the TO-263 package.

Thanks a lot in advance!

Christian Plourde

 

  • 0
    TI__Mastermind 36110 points

    The TLV1117 theta ja number uses a standard jedec high k board that uses 4 layers with 2oz copper on the top and bottom. Board is 3x3. You can find a lot of thermal information at www.ti.com/thermal.  There are several high current ldos that have a theta ja vs cu area curve. One is the TPS74301.  More copper always equals lower thetas.  Note that the TPS74301 graph shows that you get diminishing returns by using larger than 3x3 in.  If the LDO loads are on the same board, their loads can actually heat up the ldo. Thermal design is very board specific and can result in significantly different thetas than the test case. What are the electrical requirements?

  • 0 in reply to Matthew Day
    Prodigy 20 points

    It would be great to get the TLV1117 TO-263 package data into the pcb thermal calculator!

    Thanks

  • 0 in reply to Rick Pugel
    TI__Guru**** 165036 points

    Rick,

    TLV1117 in KTT package has same junction to pad thermal (0.3C/W) as BUF18830RGF which is in the tool.

  • 0 in reply to Rick Pugel
    Prodigy 20 points

    Thanks Ron for providing the comparable part number. I see from reading the Help page that the calculator is just using (theta-JC,bottom + theta-CA), so this style exposed-pad package's outer surface doesn't contribute significantly to the dissipation and relies primarily on the board traces. With this calculator, I'm getting slightly more conservative numbers than with the traditional equations, so hopefully that results in a more robust design.

    This is awesome. Thanks again!