W5500 IC hardware failure

Question

Hello everyone, I’m using W5500 chip as network module based on WIZ850io design in our custom board. We have 10 custom boards all tested and checked. They all then worked fine for more than 6 days continuously except two boards failed after about 4 days. The environment was normal for all and there was no high temperature there. When these two boards are checked and after troubleshooting we have found that w5500 has short circuit in its power lines, “VDD”, “AVDD”, “GND” and “AGND” all shorted. We then isolate the analog from the digital by removing “L5” ferrite bead. As a result, the digital side was fine and has no short circuit. The schematic below shows our design and the fault location: w55001703×921 169 KB After inspection, we observe also that “TXN” and TXP" are also shorted with “AVDD” and “AGND”. So, as seen above “TXN”, “TXP”, “AVDD” and “AGND” are all on the same node. All other pins seems fine and has no short circuit including digital side of the chip. Also, note that we have checked and removed all external components that can be faulty and making this short including “C57”, “R29”, “R30”, “R39” and the whole RJ45 connector, thus making “TXN” and “TXP” pins floating from one side, however, they are still (internally) shorted with “AVDD” and “AGND”. For the above design, please note the following: We are using RJ45 JACK (with integrated MAG) and POE+ supported as shown below: Inkedw5500_LI1298×450 49.6 KB and our POE source is using “mode A” 802.3af Standard which mix DC & signals as shown above. Due to this, we use Arduino ethernet shield design (which use POE&W5500) as a second reference besides WIZ850io. The Arduino design can be seen here: Arduino Eth. shield So, any explanation, comments, advice on this fault? Thank you,

irina · Answer

I think we can need to review your schematic and I will deliver it to the hardware manager this issue. @Scott I hope you can answer the issue.

scott · Answer

@Mohammed In my opinion, your symptom seems to have received a strong ESD shock through the Ethernet signal & Ethernet connector.Otherwise, the inside of the chip cannot be damaged. First of all, make sure you have followed our PCB design rules. https://wizwiki.net/wiki/doku.php/design_guide:hardware:start Next, your circuit’s component values are wrong. C57, C58, C59, R41, R42, R29, etc. Check out the circuit below. https://wizwiki.net/wiki/doku.php/products:w5500:refschematic You used AGND, did you make the AGND wide enough? Thank you

scott · Answer

Dear @Mohammed I don’t know the state of your PCB, so I don’t know anything about ESD. POE has nothing to do with Ethernet. In order to use the W5500, we must adhere to our design. If you don’t, we can’t support you. The wider the GND, the better the characteristics. Therefore AGND it must be a sufficiently wide design. Thank you.