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LM5143: Quickstart calculator doc giving wrong result

Andrew Massey
Prodigy 150 points
Part Number: LM5143

Hi,

We are doing a single output dual buck with lm5143

Its 17-32vin, 13v5 out 30A out and 450kHz

https://www.ti.com/tool/LM5143DESIGN-CALC

...The calculator is calling for a 7.1mR sense resistor...this is too high resistance and will not work.

As such, would you agree this calculator is not useful for us?

Also, if you  make a typo and try to correct it, then you just loose that cell completely....it either goes black, or has lots of  #'s in it.

  • 0
    TI__Guru 68917 points

    Hi Andrew,

    Go ahead and send the file. The shunt resistance is calculated from the desired current limit setpoint, which should be 130-150% of the full-load rating. As you are at 15A/phase, the current limit should be 20-23A/phase. Adding half the ripple current to get the peak current, then the shunt should be around 3mΩ.

    Regards,

    Tim