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Low Output on LM5119 DC-DC

Nayan patel
Prodigy 40 points
Other Parts Discussed in Thread: LM5119

when power up the board with 46Volts, we are only get 10Volts output and if we place about 250mamps load then drops to about 4volts.

Note we are using LM5119 in interleaved Buck Operation for single 25V @ 10A output

Also FB1 Voltage on LM51119 pin voltage is about .250volts. The output resistors are set for .8Volts at 24votls.

Nayan

  • 0
    TI__Mastermind 49671 points
    Hi
    Please check your board, start from switching node and measure inductor current.
    Do you have steady VCC voltage ?
    Regards,
    EL
  • 0 in reply to EricLee
    Prodigy 40 points
    Eric,
    Thanks for getting back. Regarding current to inductor, when I power there is no external load connected but the output stays at about 10Volts.
    Regarding VCC voltage, yes it is steady about 7.5volts and regarding switching node you mean Pin 32 (SW1) Let me verify and get back to you.
    Regards,
    Nayan
  • 0 in reply to Nayan patel
    Prodigy 40 points

    Eric,

    I measure the SW1 pin 25 (CH1) and SW2 Pin 32 (CH2) see below for detail. With 100ohms load on output.

     the Output voltage drops for 10Volts to 4.0Volts with 50Votls Input.  The values of components are from web design see below for schematic.

    Let me know if you think we have wrong values install.

    Regards,

    Nayan