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LM5122: PMP9256 design on PA2398NL

Vladimir Aparin
Expert 2610 points
Part Number: LM5122
Other Parts Discussed in Thread: PMP9256,

Hello,

I found that in PMP9256 can be used 2 types of transformers. Base case (in www.ti.com/.../snvr384a.pdf) - PA6605-AL.
As I understand some components from DNP should be installed.
Can you clarify which components should be used in case of PA2398NL? What corrections of schematics should be done?

Best regards

  • 0
    TI__Mastermind 21720 points
    Hi Vladimir,

    Thanks for reaching out to us. Since there are quite a few differences between the two transformers the current sense resistor (Rs1 & Rs2) and compensation components (R25, C25, R12, Rc, Chf) might need to be changed accordingly. Are your design parameters the same as the reference design? Is there some reason that the other transformer is desirable? Since this is a tested solution I would recommend keeping the original transformer for simplicity.

    Below are the components that should be populated if the PA2398NL transformer is used. By adding these components the VCC rail of the LM5122 will be supplied by the auxiliary winding of the PA2398NL transformer
    D4, R18, C18, D5


    Thanks,

    Garrett
  • 0 in reply to Garrett Roecker
    Expert 2610 points
    We want to use PA2398NL because it's much easy to buy it in our country. PA2398NL is cheaper that PA6605-AL. We already using PA2398NL in other projects. It's the 3 main reasons to use this transformer.
    At the same time we want use LM5122 as controller in new project.

    Can you provide detailed description about sense resistors and compensation components in this case. It's required to start a project.
  • 0 in reply to Vladimir Aparin
    TI__Mastermind 21720 points
    Vladimir,

    Just to confirm you want to have the same design parameters {VIN,VOUT, switching frequency, IOUT...} as PM9256? Please let me know of any changes.

    Thanks,

    Garrett
  • 0 in reply to Garrett Roecker
    Expert 2610 points
    We want simple conditions:
    In: 9-36 Vin,
    Out 12 V @ 3-4A.
    Schematics will be great.
  • 0 in reply to Vladimir Aparin
    Expert 2610 points

    Hello,

    We need to understand next sockets (R8, R4, R32, C24, C22, R28, R29) should be placed with Pulse transformer or not?
    Can we got recommended about it?

    Best regards, Vladimir.

  • 0 in reply to Vladimir Aparin
    TI__Mastermind 21720 points
    Vladimir,

    R8 = Don't populate
    R4 = Don't populate
    R32 = Don't populate (Lease a place holder for this component)
    C24 = Don't populate (Lease a place holder for this component)
    C22 = Don't populate (Lease a place holder for this component)
    R28 = Don't populate
    R29 = Don't populate

    Here is a good reference for designing isolated feedback networks.
    www.ti.com/.../snva005b.pdf

    Thanks,

    Garrett