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LMR64010: cycle by cycle current limit

Charles Zhang1
Expert 3110 points
Part Number: LMR64010

Hi Team,

I would like to confirm the current limit behavior of LMR64010, here is the waveform captured by my customer.

CH3: Vout, CH4: IL, CH2: Vsw

My customer uses LMR640104 to convert 11Vin to 16Vout, and LMR64010 will be still working when the output load changes from 600mA to 1.9A like the plot shown above, does it mean that the cycle by cycle current limit scheme only limits the ON time of the low side FET? If the load continues going up, LMR64010 will keep working, am I correct? If my understanding is correct, what's the potential risk if the load keeps going up?

Regards,

Charles

  • +1
    TI__Genius 13580 points

    Hi Charles,

    From customer's waveform, the LMR64010 has lost the ability to regulate the Vout as 16V Vout when Iout=1.9A, since the peak current limit has been triggered.

    You are right about the current limit function, that is, this device sample the current on the low-side FET during ON time. And it's peak current control.

    Further increasing the Iout will make the device work unproperly, such as pull the Vout further down, or trigger the thermal shutdown.

    One question: what's the inductance used in customer's application? I'd like to conform whether the peak current observed is reasonable.

    Regards

    Lei

  • 0 in reply to Lei Zhong
    TI__Expert 3110 points

    Hi Lei,

    Thanks for your reply, the inductance is 10uH. 

    Regards,

    Charles

  • 0 in reply to Charles Zhang1
    TI__Genius 13580 points

    Hi Charles,

    Thanks for your feedback. With this inductance, the max IL current is bigger than expected. Well, the comments yesterday still work.

    If available, could you provide the same waveform tested in the same conditions with another LMR64010?

    Regards

    Lei