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TPS24751: how to calculate current limit

Tony Wang3
Prodigy 90 points
Part Number: TPS24751

using TPS24751 EVB, I calculated current limit is 11A, but the efuse break on 10A, can you tell me why it is 10A not 11A.

Thanks,

Tony

  • 0
    TI__Guru** 105361 points
    Hi Tony,

    thanks for reaching out!
    It is designed current limit value is 11A. Please share your test wavefroms (Vin, Iin, Vout, timer pin voltage) to look into.

    Best Regards,
    Rakesh
  • 0 in reply to Rakesh
    Prodigy 90 points

    Hi Rakesh,

      The input is a constant +12V input from power supply, the output is connected to a electrical load.

    if I manually adjusted eload's sink current to above 10A, the efuse will trip.

    On the Page #26 of data sheet, it says peak current limit is 11A, nominal current is 10A.

    Can you tell me how the 10A was calculated?

    Thanks,

    Tony

  • 0 in reply to Tony Wang3
    TI__Guru** 105361 points

    Hi Tony,

    The current limit threshold was calculated as ILIM = (minimum value of Current limit threshold-refer page7)/Rsense=22.5mV/2mOhm = 11A(approx.). So, the circuit allows nominal load currents of 10A safely without trip.

    Figure 33 in the datasheet was taken on EVM, where the circuit breaker timer starts operation just above 11A and then trips.

    Seems I got your test data through email. I will followup.

    Best Regards,

    Rakesh