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TPS54620 short circuit condition

paul kerstetter
Intellectual 455 points

If the device is shorted for the load, what current does the translate to on the input power pins?  I understand this device has short circuit protection and limits the current to 10 Amps.  So does that mean 10 Amps will be flowing into the supply input (pin 4,5,6) as well?

  • 0
    Intellectual 455 points
    So when thinking about this device....the first thing that happens in a short circuit condition is the high side fet turns off and the low side sources the current...this continues until the output current is below low side current limit, the the high side fet is allowed to turn on. So if there is a continuous short, eventually the high side fet is going to turn on...From the data sheet I take it that the short circuit will cause the high side fet to turn off if it exceeds the 11 amps. So every cycle it will attempt to turn on but wont be able to do to the high side current limit. but i think that some current will get into the pvin pins. So the questions is what would the average current be under short circuit conditions?
  • 0 in reply to paul kerstetter
    TI__Genius 11010 points
    Paul,

    The particular current will vary a bit depending on the input voltage, the inductor (saturation) and other parameters (like switching frequency). The current from the input supply during a short circuit will be short spikes of ~ 11A - that pulse is very brief and the device enters a low duty cycle mode of operation. I measure ~ 500-700mA average input current on the standard EVM when the output is shorted. After a while, the IC overheats and turns off, cools, restarts continuously (depending on thermal management & ambient temperature).

    Steve
  • 0 in reply to Steve Widener
    Intellectual 455 points
    Thanks, that's the way i thought it would behave, just wasn't sure of the actual numbers. This is good from a protecting the board stand point and it probably should be mentioned in the data sheet since it is way better than 11 Amps continuous.