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LM25143-Q1: Remote sense for four phase application

Roy Chou1
Genius 14635 points
Part Number: LM25143-Q1
Other Parts Discussed in Thread: LM25143

Tool/software:

Hi Team,

Below is our architecture. We would like to use two LM25143(four phase) to generate 12V/90A output. But as you see, we divide the power board into two pieces. And we would like to let 12V is identical on both of PCB. 

But considering the trace loss, I'm not sure how to place the feedback resistor here. Do you have any idea? 

In addition, do you think long sync pin trace is risk here? (50cm)

Regards,

Roy

  • 0
    TI__Guru 63497 points

    Hi Roy,

    Are these two separate outputs now, one for each LM25143?

    The upper feedback resistor can tie to the positive point of load. However, the GND reference is at the controller, so it's important to use multiple GND planes to reduce that IR drop.

    50cm seems quite long for the SYNC signal - consider placing it on an inner layer surrounded by GND, so it doesn't cause a radiated EMI issue.

    Regards,

    Tim

  • 0 in reply to Timothy Hegarty
    TI__Genius 14635 points

    Hi Tim,

    1. Only one Vout with Two LM25143. (4phase with one output)

    2. But the two LM25143 is in different PCB board. I'm wondering if FB circuit is near the first board and there would be IR drop in another board.

    3. Ok, we will try to shorter it.

    For item2, do you have any idea to minimize the IR drop?

    Roy

  • 0 in reply to Roy Chou1
    TI__Guru 63497 points

    Hi Roy,

    It's likely not a good idea to have the two contorllers on separate boards with some distance between them. The master provides the COMP for the slave, so any voltage difference on GND will affect current sharing.

    Maybe a diff amp that levels shifts the COMP voltage to the slave GND might work to improve the current sharing.

    Regards,

    Tim