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LM3489 with current sense resistor

Go
Genius 4220 points
Other Parts Discussed in Thread: LM3489

Hi,

If we design the LM3489 circuit with using current sense resistor,

what point should we be careful with pattern layout? (need Kelvin sensing?)

Does anyone have a reference PCB layout for this?

Thanks

Go

  • 0
    TI__Intellectual 2320 points

    Hello Go,

    When adding a current sense resistor, in most cases the sense resistor is equivalent to the RDS,ON of the PFET in the circuit. It is arguably inherent Kelvin sensing.

    While there is no reference layout at present which I can share with you, one important point to keep in mind is the addition of the RSENSE resistor between the ISENSE pin and the drain of the P-FET . This resistor helps to prevent the increase in the set current  limit due to the undershoot in the SW node. This resistor must be used in all cases.

    Regards,

    Sourav

  • 0 in reply to Sourav.Sen
    Genius 4220 points

    Hi, Sourav

    I'd like ask you a little more about the LM3489 Layout with external current sense resistor.

    Regarding the attached file, I made an example that based on the LM3489EVM layout.

    Is there any problem, especially around the current sensing?

    any advice will be very appreciated.

    Thanks,

    Go

  • 0 in reply to Go
    TI__Intellectual 2320 points

    Hello Go,

    Ideally, the RSENSE resistor (RCS) should be as tight as possible to the ISENSE pin and the ADJ pin since this would be differential sensing. Based on the present EVM layout, the trace looks all right. I would be just careful with the vias as the tend to add extra parasitic inductance.

    Regards,

    Sourav