TPS23861: How to verify PoE PSE/PD controller work right?

Hi Kuo-Chang,

Thanks for reaching out! You can drag your schematic PDF in editing text of this thread to upload it.

For PD, you can measure the VRTN-VSS, and VDD-VSS on the TPS2373-4's pins or mounted test points / components. To measure the power interface current (IPI), you normally need cut the CAT5 ethernet cable. Try to use a current probe to select PR12+PR45, or PR12+PR78 until get the 4-pairs current (same with PR36+PR45, or PR36+PR78). 

Below is an example of PD side start up measurement. Since no active probe is used and all measurement refers the RTN ground, it shows VSS-RTN.  

For PSE, you can measure the TPS23861's DRAINn pin to AGND. 

Below is an example of PSE side start up measurement.

Best regards,

Diang

Hi Kuo-Chang,

See the measurement points on your schematic below:

PD: RTN-VSS VDD-VSS

PSE: Drain-AGND

Best regards,

Diang

Hi Hugo,

Some of links also may help:

Overview of PoE BT: https://ethernetalliance.org/wp-content/uploads/2018/04/WP_EA_Overview8023bt_FINAL.pdf

Key parts selection: https://www.ti.com/lit/an/slvaf59/slvaf59.pdf

AUX power design: https://www.ti.com/lit/an/slva306a/slva306a.pdf

More information can be found: e2e.ti.com/.../faq-tps23730-poe-pd-debug-troubleshooting-some-common-issues-and-shared-links

Best regards,

Diang