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Other Parts Discussed in Thread: LM5122, PMP, LM5122EVM-2PH, CSD18502KCS

I am designing a power supply using the LM5122 with the following characteristics.
Input: 9V ~ 20V
Output: 45V x 10A.
I would like to inform me which use mosfet in the oscillator and rectification.
The mounting for the inductor (inductance, core, gauge wires and coils)

  • Hi, Fernando,

    Welcome to e2e, and thanks for your interest in our products.

    The LM5122 is supported in the Non-Isolated DC/DC Forum. I will move your post over there.


  • Fernando,

    A good place to start is the Tools tab of the LM5122 product folder.   It has  along list of PMP designs with schematics and test resports.    You will need 2 or 4 phase boost to achieve 45V at 10A output.

  • colleague
    I own the LM5122EVM-2PH and got up the output voltage to 45V, only changing the value of the feedback divider.
    To increase the power, need to change the mosfet mosfet oscillator and grinding, I wonder what and how should I put.
    You need to change the inductor?
    kind regards

  • The easiest method to achive the 450W output you require is a 4-phase design  with 2 LM5122EVM-2PH operating in parallel.    This avoids large increase in FET and inductor current at maximum power condition,  

    The total boost siwtch current required stepping from 9V to 45V at 10A is greater than 50A. Dividing that among 4 phases limits current per inductor and FET to around 13A.    Dividing 50A among 2 phases requires more than 25A per inductor and FET.   That means the inductor size and FET size will be significant larger.   Power losses will also be concentrated in fewer components.  

  • I have two LM5122EVM-2PH boards and want to construct a 4-phase supply.  Do to the way the boards are layed out I want to dasy chain  one board and the other board as well.  I am assuming that I have one master and 3 slaves. The three slaves have FB connected to VCC and I have one compensation network?  I am not sure how to set the OPT pin or what else I need to do.

    I have an external oscillator that can provide the 2 sync signal with one of them phase shifted by either 180 or 90 degrees(my choice).  I want all converters to run at the same frequency.  I am not sure what resistors should be depopulated, populated or external wires are needed.  Can you assist me?




    Paul Crosby  TRW automotive Livonia michigan

  • Thank you for providing your email address.  I will reply directly to you.

    Best regards,

    David Pace

  • Paul,
    Thanks for the information. I'm trying to use just one LM5122, reducing costs. I will use 4 mosfet model CSD18502KCS, being for 2 oscilator and 2 rectifier. What is your opinion?