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LM5119-Q1 current share accuracy

K.Hamamoto
Guru 12155 points
Other Parts Discussed in Thread: LM5119

Hi

How can we estimate the accuracy(or ratio) of current at each phase if LM5119 is used by current sharing?

It may flows same current at each phase ideally. However it does not actually.

Regards,

Koji Hamamoto

  • 0
    TI__Mastermind 21720 points

    Koji,

    The mismatch caused by the LM5119 would come from small delay time difference from IC to IC. These timing delays will only contribute a small amount of current mismatch and this can be considered negligible. It is also important to note that the LM5119 in multiphase mode only used 1 master error amp and all channels will see the same signal at the PWM comparator minimizing any current imbalance caused by the controller.

    The major source of current imbalance come from channel to channel component tolerances. The major source of this is the inductor which typically has tolerances around 10%.

    -Garrett 

  • 0 in reply to Garrett Roecker
    Guru 12155 points

    Hi Garrett,

    Thank you for your reply.

    I understand that the timing delay is a reason of the mismatch.

    Also I think that the internal error amp gain is one of reason for the mismatch.

    How much is the variation of AOL?

    Regards,

    Koji Hamamoto

  • 0 in reply to K.Hamamoto
    TI__Mastermind 21720 points

    Koji,

    The error amp open loop gain will not play a role in multi-phase mismatch. This is due to only one error amp being used, and then tying the COMP signals of the Master phase to the slave phases. Disabling the slave phase error amps is done by pulling the FBx pin high. Please refer to this design as a good example.

    -Garrett