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TPS564247: Thermal Issue

deepak naiknavare
Prodigy 140 points
Part Number: TPS564247

I am using TPS564247DRLR for 2.8VDC with a maximum load of 2.5A in worst case peaks.

Nominal current is usually 100mA at the 2.8V output. Still i have done all the tests with 2.5A to have a worst case temperature rise.

 

I have considered rja=70deg to get this rise.

In practical i could confirm the same.

Now my point is whether this IC not rated for this high current at 2.8V output, or can i still reduce the temperature with Layout modificationsince i need to operate it upto 70deg ?

  • 0
    TI__Expert 3900 points

    Hi Deepak,

    I will check in lab, give you feedback later.

    Best Regards,

    Zhou

  • 0
    TI__Expert 3900 points

    Hi Deepak,

    1. On the EVM board, I set the same Vout =2.8V as yours. Load = 2.5A, the chip temperature is 51 degrees Celsius (picture.1). This is to meet the design requirements

    2. Yes, you can increase the copper area of the layout to increase the scattering.

    3.I don't quite understand the meaning of the specific parameters in your calculation. Can you give more details?

                                                                                            picture.1

  • 0 in reply to Harry Zhou
    Prodigy 140 points

    The below calculations are done with practical board to find the correct dissipation

    n=efficiency

    PD_total: Total power dissipation in the buck regulator

    PD_IC: (PD_total- Inductor loss) gives the dissipation only in the IC excluding the inductor loss.

    P_IC_s= just for mathcad calculation i have made it unitless.

    If i assume your efficiency of 92% as per datasheet and 12V input, the power losses will be around 0.6.

    So the temperature rise= 0.6*58C/W+25C=59 deg. (as per datasheet)

    So your EVM might be having a very low RJA of about 43C/W.

    Is it correct?

  • 0 in reply to deepak naiknavare
    Prodigy 140 points

    Correcting myself- above calculated 59 deg would be the junction temperature and case temperature is 51 as observed by you

  • 0 in reply to deepak naiknavare
    TI__Genius 13451 points

    Hi Deepak！

    As most of heat is go through to bottom side. So we think case temp is equal to junction temp.

    Shuai