I recently designed and fabricated some prototype boards based on the W5500, but I mistakenly used regular Bob Smith Termination for the differential traces coming out of my RJ45 jack with magnetics. Communication between my microcontroller and my W5500 via SPI seems to work OK, and the W5500 can blink the LINK and ACT leds, but the W5500 is unable to acquire and IP over DHCP or otherwise interact with the ethernet port on my router. My current suspicion is that my Bob Smith termination is at fault.
I’ve noticed that in the reference schematics, the W5500 has a 6.8nF capacitor on both of the RX lines, and the 49.9R resistors on the RX lines are terminated to ground instead of +3V3. What functions do these 6.8nF capacitors perform (I’m assuming an AC-pass filter of some sort)? Would the chip still work without them? What kind of issues might be caused by terminating the RX lines to +3V3 with the 49.9R resistors instead of GND?
I have uploaded my schematic as a PDF. The W5500 is on the second page.
oops.pdf (244.9 KB)
Thanks for your time!