This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS23753A: Conducted emissions fail

Part Number: TPS23753A
Other Parts Discussed in Thread: PMP8803


We have a POE design based off PMP8803. We are currently failing the conducted emissions testing. 

We have found the cause to be down to the slew rate of the main switching FET and increasing R13 on PMP8803 from 10R to a 33R brings us back within an acceptable conducted emissions limit. 

The testing + verification for this design was effectively signed off already until we hit this issue and so I'm trying to determine the implications of this change - do we need to re-run bode, transient, startup and other PSU testing or is this change sufficiently minimal that it's unlikely to affect performance? 

Any advice you have would be greatly appreciated.

Many thanks

  • Hi Pjs,

    Thanks for reaching out to us!

    Increasing R13 can results reduced Q2's Vds rising/falling slew rate to eliminate some high frequency harmonics. Then you may have improved emission test results.

    I would consider to re-run the switching transient test of Q2 and re-measure the efficiency after adjusting the R13. The other test results may not have noticeable changes. 

    Best regards,


  • Hi Pjs,

    Since we have not received your response in a relative long period, I will close this thread for now. Please open a new thread if you have any further questions.

    Best regards,