TPS2378: When use a 802.3AT PSE tps2378 can work,when use a 802.3af PSE,it will not work

The schematic of TPS2378 + TPS54561 is like below:

This design can work with 802.3at DC48V1A injector without any problems.  But once we change to 802.3af (DC48V0.3A) injector, the 48V voltage can not be stable anymore.  The voltage jumps from 5 -> 48V ,then loop from 5v to 48v  over and over.  We have changed the Rcls (r310 in our design)  to 1270ohm or 243 ohm instead of 90.9.  It does help anything.

Hi Darwin,

Thanks a lot for your reply. We have dropped loading.
The VDD_5V_POE is floating when we try at and af PSE.

Best Regards,
Nan

Thanks for confirming. Is the failure also occurring with light load like 1W at the output?

Also, after looking at the schematic, is FB22 and FB23 installed? If so, can you remove them as these should not be installed. Thanks!

Hello Darwin,
Thanks for your reply. We have removed FB22 and FB23, but the problem is still here. We may need to chang to another af injector. Could you please give some advice on these af injectors if you have experience on it?

Best Regards ,
Nan