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TPS54541 and/or TPS54341 - About behavior when the output is shorted.

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Guru 21045 points
Other Parts Discussed in Thread: TPS54541, TPS54341

Hi Team,

 

Our customer would like to know about current limit of TPS54541 and/or TPS54341.

If the output of this device is shorted at the following conditions, can this device prevent the destruction caused by the severe current?

I guess that the ramp of this current is fast.

Therefore, I worry the current limit function can’t prevent that.

 

[Customer conditions]

-Vin=19.5V

-Vout=8.4V

-Iout=4.0A

 

Regards,

Kanemaru

  • 0
    TI__Guru**** 191445 points
    TPS54541 and TPS54341 have pulse by pulse peak current limit with frequency fold back. Whe over current conditions occur, the peak current is limited to the respective current limit values plus some overshoot due to the 60 nsec internal delay. Generally speaking, this will cause the on time to decrease below the time necessary for proper voltage regulation, so the output voltage decreases. As the output voltage decreases, below 75%, 50% and 255 of the nominal value, the switching frequency is reduced by half at each boundary. So the net effect is that you will have a low output voltage with 7.5 A (typical TPS54541) or 5.5 A (typical TPS54341) current into the low impedance fault. If you expect those conditions, you should size your catch diode and inductor appropriately.
  • 0 in reply to JohnTucker
    Guru 21045 points

    Hi John-san,

     

    Thank you for the information.

    I understand that the peak inductor current of TPS54541 is around 9.05A (Ilim(max)=8.8A +⊿CLpeak=0.25A) if Vin=19.5V, L=4.7uH.

    Does the internal MOSFET of this device break down by that current?

    I believe that this device don’t break down.

     

    Regards,

    Kanemaru

  • 0 in reply to Hide
    TI__Guru**** 191445 points
    The internal transistors should be capable of handling that current.
  • 0 in reply to JohnTucker
    Guru 21045 points

    Hi John-san,

     

    Thank you for your prompt reply.

    I understand. Thank you very much.

     

    Regards,

    Kanemaru