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LM5148: Current imbalance in parallel operation

user5054474
Intellectual 450 points
Part Number: LM5148
Other Parts Discussed in Thread: LM5137

Tool/software:

Hi,

I am designing a power supply circuit with 48V input and 24V x 10A output by driving LM5148s in parallel.

The datasheet states that "dual-phase mode with accurate current sharing can be set," but how accurate can the current balance be?

For example, if the distribution of 10A is 4A and 6A, is that within the appropriate range?

For example, if it is 3A and 7A, is it unbalanced and requires some countermeasure?

Best regards,

  • 0
    TI__Mastermind 40040 points

    Hello,

    Expected to be around +/- 20% as a worse case, I would be looking to obtain around +/-10%.  if you are getting much worse than this, suggest checking your design against the calculator, then check your component section, if this all checks out, ensure you have followed the guideline in the datasheet for laying out the power stage and device and repat for the 2nd phase.

    We have dedicated dual phase controllers, like the LM5137, making the layout of the device easier.  Hope this helps.

    David.

  • 0 in reply to David Baba
    Intellectual 450 points

    Hi,

    What does "2nd phase" mean?

    The expected current is 5.1A+5.1A=10.2A, but the actual measurement was 4.853+5.394A≒10.2A.This is ±5%, so it seems to be at a reasonable level.

    The datasheet doesn't provide details,so I would like to know which component has the greatest impact on maintaining the current balance between the Master and Slave. Is it due to variation in the inductor current sensing circuit?

    Best Regard,

  • +1 in reply to user5054474
    TI__Mastermind 40040 points

    Hello,

    The offset in current sensing loop, including internal slope compensation.  Another obvious one is differences in current sense resistance and inductance.  Also, if there is a mismatch in current sensing layout it can affect accuracy.  

    The sharing looks acceptable to me.

    David.