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TPS548D21: Query on TPS548d21 Switch node pins connection to Inductor - Current density

seetaram reddy
Prodigy 30 points
Part Number: TPS548D21

Thanks John , This is Follow up related to your earlier response

As per the TPS548D21 datasheet, with the Eval board layout, considering Natural convection, below measured temperature data is reported on Pg 9, Figures 3 and 6:

40A I out, Measured temperature = 86C, Temperature rise at IC = 66C

30A I out, Measured temperature = 75.3C, temperature rise at IC = 48.3C

So we expect that for 25A load current the temperature rise should be lower than 48.3C..

In our case we expect the worst case ambient in the vicinity of the TPS548D21 chip to be around 85C

 

Can an estimate be provided for the temperature rise at IC for two cases?

  1. 20A output load current
  2. 25A output load current.

as unable to open the  link  View online

Seetaram,

Yes the power density is quite high.  At 40 A output current you may see temperature rise of 75 deg. C.  At 25 A it should be lower.  Even not considering the copper trace, The IC itself, as well as the output put inductor, will contribute to the temperature rise.  for 25 A output, I would expect the temperature rise to be about 25 deg. C. less or about 50 deg. C.  This is based on measured thermal performance as shown in the datasheet.  Let me know if you have further questions.

  • 0
    TI__Guru**** 191445 points

    Seetaram,

    I'm sure we can get the temperature rise for those two output currents based on the TI EVM board.  As you are probably aware, thermal performance is highly dependent on PCB design.  The EVM contains six layers of 2 oz copper.  Two are dedicated ground planes and three others have significant heat dissipating ground area.  To get similar results, you will need a similar PCB design.  Another detail worth noting is that the load current is NOT dissipated on the EVM PCB, it is external.  If the devices you are powering are located on the same PCB, that will contribute to the self heating.

  • 0 in reply to JohnTucker
    TI__Guru**** 191445 points

    Seetaram,

    For Vin = 12 V, Vout = 1 V and Fsw = 650 kHz:

    Estimated temperature rise is 20 deg . C at 20 A and 29 deg. C at 25 A.  Based on the PCB info above.