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LM5069: Decouple Insertion Delay and Fault timer

user5018898
Intellectual 770 points
Part Number: LM5069
Other Parts Discussed in Thread: TPS2491

Hi, 

My understanding is that the insertion delay and the maximum time before a fault condition is flagged are both set by the capacitor on the TIMER pin. Is there any way to decouple these? We have used the EVM, and the default current limit and fault timer is good, but we don't need such a long insertion delay but would like to keep the fault timer as is. Is there any way this can be done?

Thanks,

Jose

  • +1
    TI__Guru** 106201 points

    Hi Jose,

    Thanks for reaching out!

    One option is to use TPS2491 controller. It is equivalent to LM5069.

    The other option with LM5069 is to split the capacitor in two capacitors and use a switch driven from PGD like below. Please evaluate this on EVM 

    Best Regards, Rakesh

  • 0 in reply to Rakesh
    TI__Intellectual 770 points

    Hi Rakesh, 

    This really helped. Is there an app note to help with the calculation for this? I assume you would have the original Ctimer as a small value to set the insertion delay to a small value, and then have the capacitor being switch in be a larger value to have a longer fault timer?

  • 0 in reply to user5018898
    TI__Guru** 106201 points

    Hi Jose,

    No we don't have an app note for this topic. It's just a thought for the issue posted. Please ask customer to evaluate on their board.

    Correct. Start with small cap to set lower insertion delay and then switch to higher cap to have longer fault timer

    Best Regards, Rakesh