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LM5163: how to reduce Vout ripple at low load?

Dimitri Butvinik
Prodigy 50 points
Part Number: LM5163

Hi,

I made a 54V to 5V regulator using LM5163 and it works, but I have 15% output voltage ripple at very low 5mA load.

My load is always going to be low and I need to reduce the ripple to below 5%, ideally to 2-3%. Any advise how to do it?

Schematic, BOM, layout and scope images attached. Thanks

  • 0
    TI__Mastermind 34165 points

    Hi Dimitri,

    Device works on PFM mode as the 5mA is very light load, the output ripple maybe higher than normal load condition.

    You can try the TYPE2 ripple generation method, the Cff cap helps to reduce the required output ripple.

    B R

    Andy 

  • 0 in reply to Andy Chen
    Prodigy 50 points

    Thanks Andy for your quick and helpful response!

    I added Cff = 470pf and also doubled Ron to 47k to reduce Fsw to 250kHz, which helps with poor efficiency at such low load.

    Result is better than expected, device runs in CCM mode and Vout ripple is negligible 20mV.