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TPD3S014: Estimating power dissipation for TPD3S014DBVR

Jack Zhang
Intellectual 540 points
Part Number: TPD3S014

Hi, I plan to use TPD3S014DBVR to limit USB 5V VBUS power to 0.5 A out to an external USB connector per USB 2.0 spec using a 5V rail as the input to the device. How do I estimate power typical and max power dissipated for the device? Any guidance is appreciated. Thanks.

  • 0
    TI__Mastermind 18556 points

    Hi Jack,

    Assign it to Eric, and I guess you can refer to our datasheet '11.3 Power Dissipation and Junction Temperature', that has the detailed power dissipation message, thank you.

    Best Regards,

    Kuno

  • 0
    TI__Genius 11115 points

    Hi Jack,

    The majority of the power dissipation will be via the power switch.  Under normal circumstances, typical power dissipation is going to be calculated as I^2*R, where R is RDS(on) of power switch and I is the load current.  Per section 7.6 of the datasheet, RDS(on) is 97 mOhm typical, 154 mOhm max.  At 0.5 A load, this equates to 24 mW typical and 38.5 mW max.

    A transient maximum power will be encountered when the part is current limiting, although I believe this is outside the scope of your question.  The part will drop VOUT to maintain constant 500mA 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 = 0.5, so dissipated power is 2.5 W.  However, this power will be very short lived, since there is a thermal protection mechanism that disables the output when junction temperature hits 135C (datasheet section 7.6 "Thermal Shutdown").

    Finally, if you want to add one more consideration for power, we can look at supply current.  When enabled, the device requires 66 uA (typical) to 94 uA (max) to operate.  Here, P = VIN * Supply Current.  Typical power = 5V * 66 uA = 330 uW, max power = 5.5 V * 94 uA = 517 uW.  This is in addition to the numbers provided above.

    Regards,
    Eric