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UCC28064A: current sense location

Fred Cheng
Expert 5960 points
Part Number: UCC28064A


Hi team,

I wonder why there are so many location for current sense ,

one is right after the full bridge , the other is from the source the MOSFET.

May I know the difference and which one is better?

  • 0
    TI__Genius 11350 points

    Hi Fred,

    The two nodes you have circled are not the same. Different documents use varying ground symbolism which can be confusing. Essentially, the current sense resistor must go between the device ground and the system return path (which is the negative terminal of the bridge).

    Please reference the layout guideline for more info on the physical placement and connections for the current sense signals.

    https://www.ti.com/lit/pdf/slua959

    Let me know if you need more information.

    Regards,

    Ray

  • 0 in reply to Ray DiCecco
    TI__Expert 5960 points

    Hi Ray,

    understood,

    may I know why there's a resistor connection between CS and  MOSFET source ( the arrow pointed)

    what's that for ?  I didn't see that connection in some  reference designs

  • 0 in reply to Fred Cheng
    TI__Genius 11350 points

    Hi Fred,

    For clarity, I labeled the two resistors around this node. I believe your question is regarding Rs.  Rs is recommended to limit the current into CS during inrush (typically 100Ω) as that pin has a -30mA abs max limit.

    Rcs is the current sense resistor.

    Let me know if you have any further questions.

    Regards,

    Ray