W5500 PoE schematic/layout review

Question

Hi all, I just finished the design of a board which has a W5500 and Power Over Ethernet. Some feedback on the schematic and lay-out would be highly appreciated. Here is the schematic: image2070×989 243 KB 3D preview: image1283×905 131 KB Top layer: image1496×887 109 KB Inner1/Inner2 (identical): image1702×975 82.6 KB Bottom layer: image1592×1053 95.2 KB Feedback/questions are very welcome.

jessevdz · Answer

Anybody?

PaulDavis · Answer

Nice work. I’ll follow-up on your layout as PoE is in the pipeline for another project. Looking good, only sugg I’d have would be to drop 10K to 4K7 on ‘all’ the pullups. I.e. noise immunity, robust. OT: How did you managed to post a thread? I appear to be completely locked up from this platform for some strange reason. Spent 3 email addresses already (wife’s, son, mine), all the same silencing thing…

PaulDavis · Answer

Well good for you to be able to post threads, I just can’t. New Post option is nowhere to be found. However I’m receiving weird bits to the account letting me know that I’ve gained batches, getting to know you and what not. Steep arrival to a modern intranet!! Yes. I’d like to follow-u/p on your schematic eventually. However I’ve yet to get a simple and functional layout approved; two iterations failed so far. One with an analog ground plane, another without, tighter impedance matching, etc etc, nothing works. In fact it does work, I’m getting an IP and can ping but at ultra-low SPI speeds only (100kHz max sort of poor performance). As soon as I bump this up in the 0.5~1Mhz everything fails. Worrying… Once I can get to the bottom of that performance issue (hence why I need to seek the resident experts advice, and be able to post), I’ll crack on my ultimate goal - a PoE integrated solution like yours. I’ll update how things goes.

jessevdz · Answer

I would gladly have a look at your schematic/layout if you can get it posted somewhere, or just send me a DM. Maybe I can spot an issue.

PaulDavis · Answer

Both failed iterations were based off the manufacturer’s reference design. The one with the RJ45 with incl magnetic. I won’t post it here as it’s identical and I certainly don’t want to swing this thread into irrelevance. Grateful for the offer though (I could send you the 4-layer gerber/layout, which is where the problem is, I suspect). If I can’t sort it before end-of-week I’ll send this out. In a meantime I equally look forward a Wiz Team review on your PoE solution.

jessevdz · Answer

Sure, send it via DM, in the meanwhile I hope a Wiznet representative visits this thread soon.

Alan · Answer

I’m very, very sorry for being late. Do you want feedback on the circuit and PCB design? Or do you have any other problems? I’m sorry for the late confirmation. If you send all questions about POE to the email below, we can respond more quickly. Alan@wiznet.io

jessevdz · Answer

Review was handled via email with Alan, main take-aways for others: Bob-smith copper plane was not needed, as RJ45 and enclosure are both plastic. Area near the RJ45 input is now free of planes Transformer is rotated 90 degrees now, so that the input pairs are a bit longer (less critical) and output pairs to the W5500 are shorter (more critical) Other than that everything seems fine and I will move into production. Lets hope for the best