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The Exposed-Pad of TPS61251

Other Parts Discussed in Thread: TPS61251

Hi,

    If  all pins of TPS61251 are slodered but Exposed Pad,What is the impact on the chip?

Hengwei Xiang

  • Hello,

    The "Terminal Functions" table on Pg. 4 of the datasheet gives the the reasoning for soldering the exposed thermal pad as

    -mechanical stability

    -provide sufficient thermal dissipation to allow the chip to operate properly.

    Also since this pad is expecting to be at GND potentials allowing it to float could place unknown voltage potentials on this pin relative to GND.

  • Ryan May,

             Thanks for your reply.I am using the chip for converting 4v to 5v.I find output is short circuit ,however,when I take away the chip,output  is not short.I infer the chip is broken and the cause is that the EP is not soldered.Am I right  or wrong?

    Hengwei Xiang

  • Hi,

    for the thermal pad , there are three possibles:

    1) maybe the die is downbonded, that means the GND of the die is bonded to thermal pad, so thermal pad must be connected to ground.

    2)non-downbond die, maybe the package use some conductive mount compound, then actually the substrate of the die is connected to thermal pad,  in this way substrate also must be connected to GND.

    3) non-downbond die, if we use non-conductive mount compound, the die and the thermal pad is not electrical connected, the thermal pad is only used for thermal dissipation and stablization.

    for tps61251 QFN package, i tested a sample and the result is the thermal pad not short to GND, so it's the third option. 

    thanks.

    Charles from Boost converter solutions

  • Hi

    sorry for my last answer, I check with our product engineer, actually it's conductive material. so it's option 2, thermal pad must be grounded. thanks