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TPS54228: is it safe to apply 5V constantly on output side when there is no voltage applied on input side?

Hung Ching Hsu
Expert 3086 points
Part Number: TPS54228
Other Parts Discussed in Thread: TPS62097

Hi Team, 

My customer wants to know is it safe to apply 5V constantly on output side when there is no voltage applied on input side, could you kindly help confirm? Thanks.

Regards,

Jo

  • +1
    TI__Mastermind 22445 points

    Hi Jo,

    Mostly yes as this just turns on the HSFET body diode and results in a voltage Vout minus the diode drop at Vin. You need to check for any reverse current levels and ensure voltage ratings are not violated which does not seem to be an issue here with 5V. I recommend checking all 7 points listed in this app note: https://www.ti.com/lit/an/slyt689/slyt689.pdf

    Thanks,
    Amod

  • 0 in reply to Amod Vaze
    TI__Expert 3086 points

    Hi Amod, 

    Thank you.

    Customer wants to know following, could you kindly help?

    1. The value of HSFET body diode voltage drop 

    2. reverse current rating.

    From the material you shared, it says following. And TPS54228 have 2Amax Operating output current, so the reverse current rating will also be 2A? 

    "Since the input supply rail is powered from the output, there is reverse current flow through the IC to the other circuits on the input rail. The average reverse current should be kept less than the forward current rating of the IC. For example, the TPS62097 general-purpose industrial IC has a 2-A rated current. "

    Thanks.

    Regards,

    Jo

  • 0 in reply to Hung Ching Hsu
    TI__Genius 13221 points

    Hi Jo!

    Amod will reply you tomorrow!

    Shuai

  • +1 in reply to Hung Ching Hsu
    TI__Mastermind 22445 points

    Hi Jo,

    Yes the reverse current rating can be limited to 2A. The HSFET body diode drop isn’t characterized but should be in the 0.6-0.7V vicinity. Best option is to check the drop on an EVM or any test board at the reverse current you expect to flow. 

    Thanks,

    Amod