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LM5123EVM-BST: Reference design for EVM modification to support low input voltage

JH Shin
Mastermind 7830 points
Part Number: LM5123EVM-BST
Other Parts Discussed in Thread: LM5123-Q1

Hello,

My customer wants to test the operation of the LM5123EVM at input voltages as low as 3V.

Could you please provide a reference circuit for modifying the LM5123EVM-BST to support lower input voltages?

Thank you.

JH

  • 0
    TI__Mastermind 45321 points

    Hi JH,

    thank you for supporting the LM5123.

    Please note: the min voltage per spec is 3.8V for the LM5123.

    To enable the device at lower voltage please adjust the resistor divider at UVLO/EN

    With changing R15 to 45k the device should start at ~ 3.8V.

    Note: please consider that at this voltage the output power needs to be limited to a lower level.

    Best regards,

     Stefan

  • 0 in reply to Stefan Schauer
    Mastermind 7830 points

    Hi Stefan,

    Thanks for your reply.

    The datasheet below explains that LM5123-Q1 can be used from a minimum voltage of 0.8V when BIAS ≥ 3.8V. Is this a typo?

    For reference, the input voltage the customer wants to use is 3V.

    BR,

    JH

  • 0 in reply to JH Shin
    TI__Mastermind 45321 points

    HI JH,

    the statement in the Datasheet is right. So if you supply BIAS with >= 3.8 V you can go down with VIN to 3V (or even 0.8V)

    In this case set the jumper on the EVM to have BIAS connected to VOUT and and sure that for power up VIN is greater 3.8V (+ the drop of the Body Diode if BIAS is connected to VOUT) or BIAS is supplied from External.

    Best regards,

     Stefan