My own w5500 Ethernet module

Projects Networking, Protocols, and Devices
1

Hi there!

I am trying to make my own w5500 Ethernet module, I found the datasheet and a lot of helpful info here:
==> http://wizwiki.net/wiki/doku.php/products:w5500:start

In particular this diagram which does 90% of the work (also attached):
==> http://wizwiki.net/wiki/lib/exe/fetch.php/products:w5500:w5500_sch_v110_use_mag_.png

I also found this one which is very similar, it is the schematics of their own Ethernet shield:
==> http://wizwiki.net/wiki/lib/exe/fetch.php/osh:w5500_ethernet_shield:w5500_ethernet_shield_v1.01.pdf

My questions:

  1. what is the point of the resistance of zero Ohms? (on the left side, connected to the crystal input)
  2. why having 3.3V digital and analog?
  3. why having a GND and a CGND (which I guess is chassis/enclosure ground)? How to connect these if let's say I have a +12V power source which I change to 3.3V?

Thank you in advance for your help! :wink:

Cheers
Simon

PS: I have checked and read as much as I can, but please do not hesitate to move the topic or correct me if I'm not following the rules, I am new here :slight_smile:

w5500_sch_v110_use_mag_.png
w5500_sch_v110_use_mag_.png2164×1530 119 KB

2
  1. what is the point of the resistance of zero Ohms? (on the left side, connected to the crystal input)

That way you have the possibility to insert a resistor without having to change the PCB.

  1. why having 3.3V digital and analog?

To don't influence each other. That way you have a very stable power source for the Ethernet part no matter how much communication you have on the digital side (SPI bus).

  1. why having a GND and a CGND (which I guess is chassis/enclosure ground)? How to connect these if let's say I have a +12V power source which I change to 3.3V?

That's the connection to the Ethernet shielding (if using STP cabling).

3

Thank you so much pylon!

Makes more sense now :slight_smile:

I'll drop the 0 Ohm resistor then and make sure to separate 3.3v digital and analog like they do on their schematics, with an inductor.

Regarding 3), I think I understand, you mean the metal part of the RJ45 jack (on the actual cable) is connected to the shielding of the cable which is connected to the same metal part at the other end of the cable, all of that has to be grounded, is that correctly understood?

Cheers

Simon

4

Also, could someone explain the idea of having the CGND and the GND connected using a 1nF/2KV capacitor?

Thank you!

5

Regarding 3), I think I understand, you mean the metal part of the RJ45 jack (on the actual cable) is connected to the shielding of the cable which is connected to the same metal part at the other end of the cable, all of that has to be grounded, is that correctly understood?

As the shielding should be grounded on only one side of the connection they probably separated it here.