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LM5170: ISETA current margining

Jamie Shaffer1
Prodigy 220 points
Part Number: LM5170


I have the LM5170 set up with the external voltage control loop as described in the application notes. The loop increases ISETA when the output voltage is too low, or decreases when it is too high. The reference voltage used for the voltage control loop comes from a buffered DAC. I need to provide capability for both voltage and current control, such that two converters connected to one load, each controlled by its own LM5170, can match each other's output voltages while sharing the load current unevenly. What are some options for achieving this?

  • 0
    TI__Guru* 78675 points

    Hi Jamie,

    Thank you for reaching out.  If you ties ISETA pins of the two LM5170 together, they will share the load current evenly.  You just need on voltage loop to regulate the voltage, and the voltage loop produces ISETA for both LM5170 IC to use.

    Hope this clarifies.

    Best Regards,

    Youhao Xi, Applications Engineering

  • 0 in reply to Youhao Xi
    Prodigy 220 points

    Hi Youhao,

    Thanks for your response. You actually got the opposite of what I'm asking for. I would like to share the load current unevenly. Do you have any suggestions for this?

    I imagine I would increase or decrease the ISETA by some margin on one LM5170 and perform an equal but opposite change on the other.

  • +1 in reply to Jamie Shaffer1
    TI__Guru* 78675 points

    Hi Jamie,

    Sorry if I misunderstood your question.  As you may see, the LM5170's inductor current is regulated against ISETA voltage. You can alter the current sharing of the two LM5170s by offsetting the ISETA of each LM5170.  My recommendation is, let the voltage loop to control one LM5170's ISETA, and you can offset the 2nd LM5170's ISETA. This will retain the output voltage regulation. 

    Thanks,

    Youhao

  • 0 in reply to Youhao Xi
    Prodigy 220 points

    Hi Youhao,

    That is in-line with what I was thinking. Thanks for confirming!

  • 0 in reply to Jamie Shaffer1
    TI__Guru* 78675 points

    Thank you Jamie!  Wish you the good luck in your project.  Please feel free to contact us if we can be of further assistance.

    Best Regards,

    Youhao