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TPS53355: TPS53355 OC setting

Frank Xiao
Genius 12055 points
Part Number: TPS53355


hi team,

my customer uses the TPS53355 to design 12V input 5v 7A convert based on the datasheet formula. They find some boards are 7A oc. But one board  is 11A OC. They want to check whether it's normal. In my opinion, it should be normal, for we don't know the Rdson value. If i am correct, the customer also may meet 5A OC with the setting(sockets variation), correct? Thanks.

  • 0
    TI__Genius 14455 points

    Hi Frank,

       Yes, you can expect variations between parts.  You can look into the datasheet electrical characteristics to get information on what to expect for the variation.

    Regards,

    Gerold

  • 0
    TI__Guru 56985 points

    Frank,

    There is some expected variation in the OC trip point, especially when attempting to set the current limit of a 30A device to 7A.

    If the customer selected Rtrip based on a nominal 7A current limit and is measuring a nominal 7A current limit, there is a significant risk that some devices will have a current limit below 7A.  The customer should select Rtrip based on the lowest trim pin current specified in the datasheet (9.4uA) rather than the nominal (10uA).

    They should also calculate the value based on the least inductor current ripple (lowest VIN, highest inductor), and the worst case current sense voltage offset (-5mV)

    With the 6% offset from the current source and 2.5A offset from the voltage comparator, their nominal current limit should be about 10A for a minimum 7A and maximum current limit about 13A.

  • 0 in reply to Peter James Miller
    TI__Genius 12055 points

    Hi peter,

    Many thanks. In my opinion, we also don't know the Rdson. It will also influence the current limit. Thanks.