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LM25085 CV+CC and UVLO

NPeter
Prodigy 40 points

Hello everyone!

We would like to use this IC in CV+CC operation according to the AN-2157 application note. (Parameters: Vout = Vin = 9...18 V, Iout = 4...6 A (adjustable))

However, we need an UVLO protection feature as well activated when the input voltage drops below 8 V.

Is this possible by using the RT pin of the IC? A simple voltage divider could pulls that pin below 0.73V, but in that case On-time setting could be wrong during startup.

Another question: By using the same circuit as in the application note AN-2157 is it possible to place the current sensing resistor to the input line instead of the output line?

Thank you very much for any help in advance.

  • 0
    TI__Genius 11490 points

    It is possible to use current sense resistor on the input line. It needs to be filtered better because input current has lot more ripple.

     

    It is not recommended to use the RT pin as a precision UVLO pin. The shutdown threshold of the RT pin is not very accurate. You can however use this pin (pull down to ground) to shutdown the part. But when not in shutdown the pull down path (a FET e.g.) should be open circuited so as not to affect the on-time setting.