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LM5166: COT vs PFM

Paul Dye
Prodigy 180 points
Part Number: LM5166

Hi,

Does anybody know if there is a document which clearly describes the difference & merits between Constant On Time and Pulse Frequency Modulation modes?

I've read the datasheet several times but couldn't really put up a strong argument when to use either mode and at what point the transition is from using one to the other.

Thanks

Paul

  • 0
    TI__Mastermind 23845 points
    Hi,

    I believe the datasheet page 16 - 18 waveform describe the difference between the two operation.
    In general the PFM mode you will have more ripple at the output voltage because of the 10mV on the FB node. This way you switch less and you have higher efficiency at light load compared to Constant on time. You can see a longer sleep time on PFM mode

    The constant on time on the other hand will have less output voltage ripple for the same condition but with tradeoff of lower efficiency at light load.

    www.ti.com/.../lm5166.pdf


    Thanks
    -Arief