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TPS74401-EP: Temperature & Current withstanding capacity of TPS74401-EP

James
Prodigy 190 points

Part Number: TPS74401-EP

Hi there, 

Currently, i am developing an electronic system using the TPS74401-EP LDO. 

The TPS74401-EP is used to drop a 3.3V main power to 1.2V Processor core power.

I expect that an output current of a 1.2V supply power is required approximately 2.2A.

If the development system operates at -40 to 125 ° C, will the chip break down?

(I calculated the allowable operating temperature as follows.

Top = Tj - Rjc(Junction to bottom case thermal resistance) x P

      = 125° C - 2.4° C/W X 4.6W

      = 113.96° C)

through the above calculations, I derived the operating temperature of 113° C. Is the above calculation correct?)

please answer my question.

  • 0
    TI__Mastermind 20045 points
    Hello,

    Please see our application note on thermal metrics for more details and caveats to the below information: www.ti.com/.../spra953c.pdf

    However, it does not appear your calculation is correct. If the ambient is 125C you will need to add the power * R-theta. It depends on how your device is heatsinked as to which R-theta metric you will use. You also need to add the R-theta of the heat sink. For example, if your bottom heat sinke (which may be the PCB) has an R-theta equivalent of 10C/W (that the IC bottom is thermally connected to) your calculation would be:

    Tjunction = Tambient + [(R-theta-Jbottom + R-theta-heatsink)*Power)
    Tjunction = 125 + [(2.4+10)*4.62] = 182C

    As you can see from the above equations, unless you lower Tambient you will not be able to meet the maximum junction temperature of 125C.

    Thanks,
    Kyle