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LM25069: Can I remove the current sampling resistor from the circuit?

user5749616
Prodigy 20 points
Part Number: LM25069

See my question in the title. 

I use LM25069 on a power supplier board, while my upstream DC/DC converter has build-in over-current protection functionality, in such senario, Can I just delete the current sampling resistor(R30 in the picture below), connect Vin(Pin2) and SENSE(Pin 1) directly?

  • 0
    TI__Guru 57737 points

    Hi,

    The sense resistor is required to provide below protection features,

    • In-rush Current Limit during startup
    • SOA protection of external Mosfet during Startup and Fault conditions
    • Over Current and Short Circuit Protection

    Removing the Sense resistor will not provide you any of the above protection features. This will leave you with only UVLO and OVLO features that can be useful.

    In an way, inrush current can still be controlled by adding a capacitance at Gate but you need to make sure that the FET is operated within its SOA region.

    If you don't require the above stated protection features, may I know what is the purpose of using LM25069 in your system ? 

  • 0
    Prodigy 20 points

    Praveen:

    The figure below depict the design purpose of the LM25069, there're 2 cards in the system, the card might be inserted/deserted when the system is alive.

    Actually, the digital power brick supports "Droop Load Sharing", OVP/UVP/OCP, but it can not handle the in-rush current when hot-attached,  do you have any suggestion to make it better?

    Thank you.

  • 0 in reply to user5749616
    TI__Guru 57737 points

    Hi,

    Can you confirm if my below understanding is correct ?

    Is LM25069 at the output of one of the cards and there is a possibility that another card can be connected at the output of LM25069 when it is ON. During this condition, you require inrush current limiting, right? 

    Inrush current limiting happens only during startup. If my above understanding is wrong, please elaborate the use case with detailed block diagram.

  • 0 in reply to Praveen GD
    TI__Guru 57737 points

    Hi,

    Can you please respond to our above query. If your query is solved, can we close this thread ?