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TPS2041: Power Estimates Question

Jack Zhang
Intellectual 540 points
Part Number: TPS2041

Hello, I am trying to use the TPS2041D in order to limit the current for a USB 5V output to 500 mA per USB 2.0 specs. I am doing some typical and max power estimates for a PCB design in order to provide data for thermal analysis. Worst case would be to 85C. The datasheet states a continuous total power dissipation for various TA temperatures for the D package, and at T@ = 85C, the power dissipation is 377 mW. Is this considered max power? Could I get some advice on calculating typical and max power based on my application? If needed, I could provide a schematic snippet of the circuit. Thank yo for your time.

  • 0
    TI__Mastermind 18556 points

    Hi Jack,

    Assign it to Eric, who is responsible for US.

    Best Regards,

    Kuno

  • 0
    TI__Genius 10765 points

    Hi Jack,

    The majority of the power dissipation will be via the power switch.  Typical power dissipation is going to be calculated as I^2*R, where R is the power switch.  At 85C, rDS(on) is specified as 90mOhm.  For a 500 mA load, this produces 22.5 mW.

    Max power will be encountered when the part is current limiting at 900 mA.  The part will drop VOUT to maintain constant 900mA output.  The power dissipation is now (VOUT-VIN)*I.  Worst case scenario is if VOUT is shorted to ground.  This theoretically means VIN = 5, VOUT = 0, and IOUT = 0.9, so dissipated power is 4.5 W.  However, this power will be very short lived, since there is a thermal protection mechanism that disables the output when junction temperature hits 140C.

    This is the first time I've seen a "Dissipation Rating Table" for one of our devices.  I believe this is a packaging characteristic and is not specific to this device.

    Regards,
    Eric