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Original question:

TPSM5601R5H: EMI Filter requirements for TPSM5601R5HRDAR

TPSM5601R5HE: Calculating Heat Dissipation/Efficiency at Different Ambient Temperatures

Michael Falzone
Prodigy 20 points
Part Number: TPSM5601R5HE

Hello All,

I am new to reading these datasheets so I am having a bit of trouble.

I would like to to estimate the efficiency/heat dissipation for this device under a load of 300mA at 15V, and an input of 28VDC, but at an ambient of 50 DegC and 75 DegC. I don't see any information on this or a clear way to translate the given values under figure 7-7 and 7-8 to different ambient temperatures. I don't see any other data at all relating to higher temp operation. I have a rough idea of the size of the PCB it will be on but not much else around the component if that helps. Is there some kind of linear approximation or rule of thumb? Maybe a simple multiple for scaling up with temp? I'm certain this will help me down the road with the rest of the components too.

Thank you for the help in advance.

  • +1
    TI__Guru* 75270 points

    Hi Michael,

    Thank you for reaching out.  There are a few ways to help you out.

    1. Order an EVM and set the board to 15Vout at J6 Header, and run the test to measure the efficiency and temperature.  You may run for >10 min or more to get stable temperature rise.

    2.  Use our Webench tool, and give the operating conditions of your Vin, Vout and Iout, and also put the ambient temperature 50C or 75V, and create the design. Then click EXPORT tab, the estimated efficiency and IC Tj should be given in the list or Operating Values (you need to scroll down to find that section).

    3. Refer to datasheet Figure 7-7, and it is the efficiencies measured under 24Vin for different Vout, including 15Vout. Then from the efficiency get the efficiency and hence the power losses. Then use Rtheta_JA from the thermal metric table on page 6 of the datasheet to get a quick estimate of temperature rise from 25C ambient.  From there add the ambient temperature difference to estimate the final temperature results. 

    Hope this clarifies.

    Youhao 

  • 0 in reply to Youhao Xi
    Prodigy 20 points

    Hi Youhao,

    Thank you for replying to my question so quickly. Option 2 has solved my issue, and has for the rest of my components as well! One last clarification Id like is would I be able to solve for the efficiency at 75DegC using method 3? I think this may only give me final ambient temp information rather than power dissipated right?

    Mike.

  • 0 in reply to Michael Falzone
    TI__Guru* 75270 points

    Hi Mike, 

    Method 3 can be used as a quick estimate and you may guess up to 1 to 2% efficiency drop at elevated temperature to 75C.

    Hope this helps.

    Thanks,

    Youhao