LM5022: PMP20058

Andrew Shinn

Part Number: LM5022
Other Parts Discussed in Thread: PMP20588

I have copied the PMP20058 POE reference design to my circuit board with all the same parts including the Coilcraft transformer. My Vin is 12V and I expect 54V output. My design does not work, there is no output. Can you provide some troubleshooting tips based on the PMP20058 schematic where I can start looking to find the issue? Are there changes I can make to the circuit to force it to start up so I can then continue to trouble shoot? Are there test results and waveforms available for the PMP20058 circuit that I can compare with my circuit.

over 4 years ago

0 Youhao Xi over 4 years ago

TI__Guru 68775 points

Hi Andrew,

Thank you for using the LM5022. Please send your native schematic that you used to create your own PCB, and we can check is there is anything wrong during copying the schematic.

Do you mean PMP20588? If yes, the test results are at the following link

https://www.ti.com/lit/pdf/tidudc7

Please be noted that we will be able to offer follow-on support next week. Wish you a happy Thanksgiving!

Thanks,

Youhao Xi, Applications Engineering

0 Andrew Shinn over 4 years ago in reply to Youhao Xi

Prodigy 60 points

ER120901-011S-03-A01.pdf

0 Andrew Shinn over 4 years ago in reply to Andrew Shinn

Prodigy 60 points

Hi Youhao,

I found out the issue and have fixed it. I had to remove U22 an OP-Amp connected to the COMP pin that I was using to try to make a voltage monitor circuit.

I have found however that the output will droop if I try to draw more than 1 amp from this circuit. What should I change or measure to determine where the issue with higher current is coming from?

Thank you for your help,

Andrew Shinn

0 Youhao Xi over 4 years ago in reply to Andrew Shinn

TI__Guru 68775 points

Can you show me the C44 voltage when you loose the output regulation (Iout>1A)?

Thanks,

Youhao

0 Andrew Shinn over 4 years ago in reply to Youhao Xi

Prodigy 60 points

Hi Youhao,

I have found the source of my problem. The 12V supply I am for the input to the Isolated POE converter was limiting the current.

Your POE design works exactly as expected.

Thank you for your help, sorry to waste your time.

Andrew

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LM5022: PMP20058