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LM5122: LM5122 Transfer voltage issue

every hsiao
Prodigy 20 points
Part Number: LM5122

DC power supply setting is15V.
DC power supply would become 13V after power on, and the voltage and current would always jump.
The DC-DC Converter board turns out the voltage without boosting but the voltage drops to 10V.
LM5122 expected function: input 8V~20V, output 55V

Please help us to help clarify the problem.

Thank you....

 

Best Regards,

Every_Hsiao

 

  • 0
    TI__Guru 68675 points
    Your high side FET is in wrong polarity. The source should be on the SW node side, and drain on the output side.
  • 0 in reply to Youhao Xi
    Prodigy 20 points
    I follow the your suggestion and adjust the direction of U1.

    The phenomenon is as follows:
    1. DC power supply setting :15V/0A
    Input voltage/ Current:3.3V/0A
    Output voltage:3.3V

    2. DC power supply setting :15V/1A
    Input voltage/ Current:13.6V/0.36A
    Output voltage:14.1V

    3. DC power supply setting :15V/2A
    Input voltage/ Current:13.3V/0.45A
    Output voltage:13.96V

    Maybe there are other problems....