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LM5017: FlyBuck-Design with 4 isolated output (with complete channel-to-channel isolation)

Martin Seeger
Expert 5411 points
Part Number: LM5017
Other Parts Discussed in Thread: PMP, SN6501

Dear Team,

I am looking for a way to build an isolated DC/DC with 4 isolated outputs where each output is completely separated.

High Level Specs:

  • 12V in
  • 4x isolated output: 5Vout with ~250...300mW per channel
  • Thinking about it, I think I could also use the non-isolated output, with 5V/~250...300mW

I fancy a FluyBuck design and found a similar design, the PMP9460, but the channels are not isolated from each other:

Is there any limitation if we want to separate the outputs? 

The load should be quite equal (4 input channels with same ADCs...)

Looking forward to your feedback.

Best Regards
Martin

  • 0
    TI__Mastermind 23845 points
    Martin,

    I believe that the limitation will be making sure that the secondary current does not trigger the current limit of the part as well as not saturating the transformer. If the power levels on your design is similar to the PMP design, you might want to work with the transformer manufacturer to see if they can isolate all 4 outputs and how tight their coupling. Leakage inductance is also should be minimized for minimizing regulation error because in Flybuck, all of these outputs are not regulated. Flybuck only regulates the primary output. For the secondary, you need a zener to make sure that you dont overvoltage the output.

    Hope that helps

    Thanks
    -Arief
  • 0 in reply to Arief Hernadi
    TI__Expert 5411 points
    Arief,
    thanks a lot for the answer.
    Okay, let me see. I agree that a 4-output transformer & global current limit might be a challenge. Maybe 2x FlyBuck could be an option vs. 4x SN6501.
    Keeping you posted.
    Best Regards
    Martin