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:
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:
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?