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LM25141-Q1: Current limit point not correct

Eddie Chen1
Prodigy 150 points
Part Number: LM25141-Q1
Other Parts Discussed in Thread: LM25141, LM5141

Hello,

Attached file for you reference, I meet a issue about current limit set point.

The inductor current is triangular but sense voltage not so.

When I test OCP, the result actual value is lower than theoretical value.

I not sure why the sense voltage is not triangular.

Could you help...

0803_LM25141.xlsx

  • 0
    TI__Guru 72845 points

    Hello

    This looks like it may be some kind of capacitive coupling.

    Maybe from the MUX or the inductor.

    First i would test by connecting the sense lines directly to the

    sense resistor, without the MUX in the circuit.

    Next, i would try a different inductor with less capacitance (higher self-resonant-frequency) and see if that helps.

    Also, be sure that your sense lines are not running near the

    inductor or switch trace on the PCB.

    Thanks

  • 0 in reply to Frank De Stasi
    Prodigy 150 points

    The first and next way I try, then not improved.

    There are two LM25141 design in my schematic : 12 to 5V and 12 to 3.3V, both of them meet same issue.

    I also measure the waveform of LM5141 EVB, the waveform is attached file. Under condition Fsw=2.2MHz, the sense voltage seems not like  triangular.https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/196/waveform.7z

  • 0 in reply to Eddie Chen1
    TI__Guru 72845 points

    Hello

    I would increase the current limit threshold in order to compensate for the spikes on the waveform.

    You could also try to increase the filter time constant on the current limit filter.

    Thanks