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LM5170-Q1: Ripple current calculation when working with 6 phases

morh
Prodigy 20 points
Part Number: LM5170-Q1

Hello,

I am using the LM5170Q calculator.

I want to use 6 phases.

i choose the ripple I want to achieve. the result I get is that the more phases I add the larger each phase inductor I need.

when working with interliving multiphase the result shout be the opposite.

as much phases I have, each inductor should be smaller  due to interliving ripple cancelation.

How can I calulate the inductance needed to get 3% ripple current with 6 multiphase interliving? (that is a buck current source) 

Thank you,

Mor. 

  • 0
    TI__Mastermind 21720 points
    Hi Morh,

    Assuming the output current stays the same, the more phases that are added the inductance value should be higher. This is because the average current per phase decreases with each phase added. To keep the same ripple ratio with a smaller average current the inductor must be larger.

    The 3% ripple current spec is just the sum of all the inductor currents that are phase shifted. These can be added together and then the inductance can be backed out of the equation.

    Thanks,

    Garrett