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TPS5450: Max. power (or current) @12V output?

durmus
Prodigy 40 points
Part Number: TPS5450

Hello community,

I've been using TPS5450 for 2 years in my project. My use case:

- input voltage: 24V

- output voltage: 5V

- output current: 2A (max)

When I review the datasheet, there is one thing that's been always bugging me. There is no reference to a max power output neither in electrical characteristics nor in any graphs. Of course it says max continuous current is 5A. But it does not specify any output voltage for that current value. I have always assumed it as 5A @ 5V. And since it satisfies my use case, I did not worry much about it.

However, now I need to use a 12V output and I need about 25W max output from that. In summary, the new use case will be:

- input voltage: 24V

- output voltage: 12V

- output current: ~2A (max)

So, my question is what is the max current at 12V output voltage? Looking at the datasheet, it seems that max output is 5A no matter the output voltage. But it seems odd to me. Is it really the case? Will TPS5450 be able to deliver 5A of current at 12V output voltage (60W !!!)?

  • 0
    TI__Guru**** 191445 points

    Generally the device is limited by IC power dissipation at any output current less than the current limit.  In low duty cycle applications where VIn >> Vout, the catch diode will be dissipating most of the power.  For high duty cycle operation, the opposite is true. the IC high side FET will dissipate most of the power.  If you look at the general loss conditions in section 10.3 of the datasheet.  You can see the relationship of Vin and Vout to the conduction loss, switching loss and quiescent losses.  You do need to be somewhat careful with TPS5450 and high current operation as that is nearing the package limits for power dissipation.  See the thermal parameters in section 6.4.