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LM5158: Questions of DRV2603

Jimmy Lai
Expert 6845 points
Part Number: LM5158

Dear Team,

Please help confirm about LMf5158 UVLO RUVLOT and RUVLOB value by today.

Our customer would like to have 47DC ON and 36VDC OFF. Thanks a lot.

Many Thanks,

Jimmy

  • 0
    TI__Mastermind 21990 points

    Hi Jimmy,

    Thanks for using the e2e forum.
    For setting the UVLO trigger levels, customer can use our quickstart calculation tool to choose suitable values for the voltage divider.
    https://www.ti.com/tool/download/SNVR511

    Please let me know if they have any questions on the tool.
    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    TI__Expert 6845 points

    Hi Niklas,

    I download calculator and fill in my requirement.

    Please help confirm enclosure UVLO data is workable. Thanks a lot.

    Many Thanks,

    Jimmy

  • 0 in reply to Jimmy Lai
    TI__Mastermind 21990 points

    Hi Jimmy,

    The two different setpoints for turn-on and turn-off are generated by an internal hysteresis. If the difference between the setpoints is larger, the resistor values need to be higher as well to achieve this.

    Even though these settings are feasible based on calculator, the design might become at risk for interference problems.
    E.g. with a 1.8MOhm resistor at the UVLO pin, the signal becomes more vulnerable for external noise coupling into the signal.
    They would reduce this risk if the difference between the two threshold would be smaller.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    TI__Expert 6845 points

    Hi Niklas,

    Thanks for your great support always.

    Actually, I can’t get the point.

    Please help confirm enclosure UVLO data is workable. Please find the attachment.

    Thanks a lot.

    LM5157-58_Excel_Quickstart_Calculator_for_Boost_Converter_Design_V1_0_0 UVLO 1130129.xlsx

    Many Thanks,

    Jimmy

  • 0 in reply to Jimmy Lai
    TI__Mastermind 21990 points

    Hi Jimmy,

    Thanks for sending the filled calculator.

    Let me put the UVLO explanation in another way.
    For an ideal system, the UVLO feedback divider will work just fine and the device will turn on at 47V and turn off at 36V.
    In the physical application, there will be noise and interference and the larger the resistance at a sensing signal, the more susceptible to noise it becomes.

    A good example to see this is by building a feedback divider system with two resistors >10M Ohm and hovering with your smartphone over the circuit.
    The noise emitted from the phone will interfere with the sensing signal and may cause oscillation.
    The the two resistors of the feedback divider are only 10kOhm each, the signal will be robust again external noise.

    The UVLO signal is not required for the regulation of the device, so noise should not harm the circuit. Only if the noise is so large, that it causes oscillation below the UVLO threshold will become a risk, as it will disable the device temporarily.

    Best regards,
    Niklas