Wiznet w5500 schematic layout verification

Hello ,
We are designing our custom PCB using W5500 's reference design. We wanted to make sure that it is thoroughly verified by Wiznet technical experts before going for mass manufacturing.
Please find the attached schematic and layout and suggest any changes or improvements are needed?

Thanks ,

The circuit looks fine. However, when designing a PCB, the Ethernet line should be designed as a differential pair. It is recommended that the impedance be adjusted to 100 ohms.

Hi Alan,
Thank you for your response. We are facing one more issue while using wiznet w5500. We have observed that whenever inductive load such as contactors are triggered near w5500 circuit,
it resets. We had put the query before on this link : W5500 False Reset due to AC switching noise - #6 by ayushjain1912 . Please let me know if you may add anything more.


Is “Reset Line” the W5500’s “Reset Line”?
Every time the inductive load you mentioned is loaded, the surge power splashes too hard… It doesn’t look normal. I think we need to turn it on properly first. Isn’t the GND line firm?

I replied to you via link.

Hello Alan,
Thank you for your response. Yes, the reset line is W5500 reset line. By “turn it on properly first”, do you mean W5500 or the inductive load in this scenario? We have the GND plane on the entire PCB.

It meant that we need to get all the VCCs right first. It is strange that the VCC bounces like the image above depending on the induced load. It’s sticking out too much.

Hello Alan,
In our system, input supply is clean. There is no VCC bouncing as shown in your image. We have microcontroller which works fine, only w5500 resets in above case.

Is that so? Can you tell me a more accurate situation? I don’t think I know the exact situation.

If you send me the whole circuit diagram, it will be easy for me to figure it out.

Did you find a solution to this? If so, please help.
I am facing a similar issue, despite having a snubber and MOV across the contactor which is being operated through a relay (with an amp and flyback diode) and a shielded ethernet cable and proper earthing - the MCU doesn’t reset but the ethernet connection is lost upon contactor operation especially while turning on.

Thanks in advance.

Unfortunately the problem persists. So we have made a peace with recovery method. Whenever w5500 resets due to contactor switching, we connect it immediately. Let me know if you have tried any other method.


I did get it to work - but not ideally.

  1. Handle resets in the firmware (takes a good couple of seconds but reconnects) (just like you did - please let me know if it can be done faster)
  2. Suppress the surge at its source - RC Snubbers, TVS Diodes & MOVs should help.
  3. Reset Monitor IC with both the MCU and W5500 Reset pins (Larger capacitors and smaller pullups)
  4. Grounding the Ethernet cable shield before the RJ45 Port on the board and then using an unshielded cable to make the connection (used a makeshift surge suppressor to do this).
  5. Proximity of the board itself and the ethernet cable from the AC contactor and current carrying wires created a huge difference.
  6. Use zero-cross SSR for control instead of electromagnetic relay.
  7. Best if a DC Contactor with a flyback diode is used - nothing like it.
  8. Isolation Transformer along with line filter for the SMPS of the Controller board.

I wasted a lot of time making a controller board using this chip only to learn that it may be good for consumer applications and not industrial or rugged applications (although advertised otherwise).

Also, if you are aware of any alternatives for an industrial environment, please let me know - what do you think about the ENC28J60?

Thanks, I hope this helps.

Hello everyone,

I apologize for posting in this topic but I am unable to create a new topic.

Anyways, I need some clarification regarding one of the pins for the W5500.

In the datasheet, it says that Pin 23 needs to be tied to ground while on the reference schematic it is not connected to anything.

So what should I do regarding this pin


I am using the W5500 chip in a client project. I lifted the schematic mostly from the Arduino Ethernet shield and also the recommended schematic for the chip. I had a small amount of boards already produced that uses this and the ESP32 as the main controller.

I am currently experiencing a weird hardware issue where the chip itself intermittently communicates with the ESP32 and intermittently communicates with my MQTT server.

I say intermittently because I have tested this on at least 4 different networks and what happens is that the board loses communication/connection and after sometime it comes back. Sometimes the ESP32 is unable to detect the chip, other times, the W5500 is unable to connect out. And while the board is sitting there, connection is mysteriously restored and after sometime, it is lost again.

Now, I am really confused as to why this is happening, I have checked back with my schematic and everything seems to be in order. Maybe I am missing something really simple.

Could I get a second pair of eyes to look over the schematic for the ethernet controller chip is see if everything is in order?

EthernetController.pdf (52.6 KB)

Here is the response concerning your inquiry about the W5500’s RSVD pin.

Oh dear… the value is too big, if the dateline has such a large cap, it’s a problem.

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Please share the details again by e-mail. Circuit and Gerber as well.
Thank you.


Hello Omkar,
I am also facing same issue, could you please share your updated schematic & layout for reference , I will also update the schematic accordingly It will be a great help. looking support from your side.