Dear Team
I designed TPS23755 based on the evaluation board, but when I tried to operate it, it did not pass through the detection phase.
I will send you the schematic and waveforms so you can check.
PoE injector: TP-Link TL-PoE150S
[VPD - VSS]
Thanks in advance
Dear Sir/Madam,
Thanks for reaching out to us!
From the waveform seems the detection failed and it did not go to classification step.
To pass the detection, you should have correct detection resistor and capacitor. The 24.9-kOhm detection resistor is correct. The detection capacitance between Vdd-Vss should be less than 0.15 uF for robust detection. You could try the methods shown below and let us know if you have any further questions.
1. Could I see the full picture of this rectifier circuit? It might be the reason of the failed detection. You may try to do desolder this circuit and try again.
2. In rare cases, the shielded ethernet cable or other PCB parts have larger parasitic capacitance which could cause detection failure. You may try to replace C1219 from 0.1uF to 0.047uF and try again.
3. Short FIL1201 and FIL1202 and try again.
4. Using TI's TPS23861EVM and BOOST-PSEMTHR-007 with our GUIs could help to diagnose the detection issue. You can request free samples via the link below (search by the part# and request 1 free sample for each of them). Meanwhile one USB2ANY adapter is also needed.
https://tisamples.ti.com/order/tisamples/en/
Best regards,
Diang
Dear Sir/Madam,
Glad to hear that you passed the detection! May I know what was the root cause of that?
For 8.2.2.5, if there is no classification resistor, the detection current should be 0mA. It still can pass the classification and the PSE will consider the PD is Class0. If you are looking for a different load power than Class0, please choose a proper classification resistor.
Best regards,
Diang
