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TPSM84209: Temperature rise for a 1 Amp 24V to 5V working condition

Marco Bedani1
Prodigy 40 points
Part Number: TPSM84209

Hi all,

we realized a board with a TPSM84209 to generate 5Vdc from 24Vdc: find attached the electrical diagram and two pics of the layout (where you can see, highlighted, the extension of the 5V pad on the top layer and the inner3 layer).

The average current required from the 5V is less than 1 Amp and in these conditions the chip reaches a temperature of about 55° C (room temperature is 25° C).
This temperature rise seems to me a little higher than what I would have expected (also considering that the a TPSM84209 could source up to 2.5 A).

What do you think? Any suggestions about this topic?

Thank you,

  • +1
    TI__Mastermind 49370 points

    Hi Marco,

    The schematic and layout are blurry. I can not see them clearly. But 55C temperature at 24Vin/5Vout/1A looks reasonable. From EVM user's guide Figure 4-2 efficiency curve, the efficiency is around 86% at 24Vin, 5V/1A condition, So the rough power dissipation is 5V*1A/0.86-5V*1A=0.814W. The Junction temp=25C amb+0.814*32.7(RthetaJA in datasheet page5)=51.62C.

    TPSM84209 can support up to 2.5A at 12Vin. For 24Vin, 5V output, the output current will be lower according to EVM user's guide efficiency curve Figure 4-2.

    Thanks,

    Nancy