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LM5019: Output volatage is higher than calculated value

Part Number: LM5019
Other Parts Discussed in Thread: TPS23861,

Dear sirs,

I am making a application boad using LM5019 for supplying isolated 3.3v for TPS23861.

I followed same schematics as TPS23861EVM-613;

My schematic is as followw;

The values of L,R,C are same as TPS23861EVM-613 but our output voltage is about 4.0V.

(I expected 3.3V and I checked the output of TPS23861EVM-613 is excatly 3.3V)

Are there anything I have to check for this issue ?

I attached the schematic and layout for your reference.


HirotoPOE_Schematic.pdf3.3V_ISO review.ppt

  • Hello,

    Looks like C186 and C 187 are far from the device. however, the issue maybe related to your ripple injection. Please check R267, it appears to be 10k. please refer to the datasheet Table1 on page 13. Looks at Type I ripple and calculate the correct value for R267.

    hope this helps?

  • Hi David,

    Thank you for your suggestions. I will check them.

    I monitored the output voltage of our application board;

    (Ch2 is output and CH1 is input which is 48V)

    Oscillating ? DO you have any idea about this cause ?

     The below monitor is TPS23861EVM which is very stable at 3.3V.


  • Hi David san
    Sorry, I misunderstood your point.
    R267 is 10k instead of 10 of TPS23861EVM.
    Thank you for indication. I will replace and check it.

    Thank you again.