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PMLKBOOSTEVM: LM5122 Inductor current was detected under 0 in DEM

Zhuoxun Liu
Prodigy 60 points
Part Number: PMLKBOOSTEVM
Other Parts Discussed in Thread: LM5122

Tool/software:

Hi expert,

In experiment 1, I set J16 open which means DEM setup,

and Vin=15V Vout=24V Iout=0.2A , which means the circuit was running under DCM.

 

but I found that inductor current was below zero which is not consistent with theoretical analysis in DEM. Could you please help me solve this problem? Thank you!

  • 0
    TI__Mastermind 30160 points

    Hi Zhuoxun,

    Thanks for using the e2e forum.

    I agree that during DEM mode, the LM5122 should not allow negative current through the inductor.
    Setting J16 to open should also be correct in setting the device to DEM mode.

    Could you check if this is a measurement error and there is a little offset on the current sensing?
    If you reduce Iout, it should become more clear if the device is actually operating in FPWM or DEM mode.
    You can also set the J16 jumper to GND (DEM with skip cycle) to check if the behavior is identical.

    Best regards,
    Niklas