---
title: "layout question regarding the reference schematic"
url: "https://maker.wiznet.io/forum/12295"
markdown_url: "https://maker.wiznet.io/forum/12295/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "jnewcomb"
created: "2017-05-19T13:35:24+09:00"
last_activity: "2017-05-19T15:20:38+09:00"
language: "en"
views: 1251
replies: 3
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# layout question regarding the reference schematic

## Question

Asked by jnewcomb on 2017-05-19 in Ethernet Chips.

Hello - I have a layout question regarding the reference schematic for W5500
<http://wizwiki.net/wiki/lib/exe/fetch.php?media=wiznet_schematic:ethernet_chip:w5500_sch_v110_use_mag_.pdf>
Its a shame no PCB layout is provided…

Should I locate R1 R2 R3 / R6 R7 - near(er) the W5500 chip or the RJ45 socket? Which side do they ‘terminate’?
Where is it best to put C9 C10 - near(er) the W5500 chip or the RJ45 socket?

I’ll locate R21 to R24 near the W5500 - i think that’s obvious.
Thanks…

## Replies

### Reply 1 by Eugeny, 2017-05-19

You can look in here into [layout guide for W5100](http://wiznethome.cafe24.com/wp-content/uploads/wiznethome/Chip/W5100/Hardware/w5100_hardware.zip). Principles for W5500 are the same.

In my experience, most critical are:

- crystal placing;

- GND planes;

- trace routing (shape, closeness of + and -, their length)

Regarding block A and B: I examined several PCBs with other chips (Intel) and they have relatively long traces between chip and magnetics, A and B located somewhere in the center of pathway. Thus your task would be just keep + and - traces as short as possible, as close to each other as possible, as mirrored as possible, and place these resistors/caps in the most convenient place.

### Reply 2 by jnewcomb, 2017-05-19 (in reply to reply 1)

Thanks - i didn’t know about this document.

But very odd…
The schematic for the W5100 has C3 to GND
:whereas:
W5500 schematic connects TX+ TX- via 49.9R to 3V3A.

Mmm. Very different… I hope its not a mistake… I’ll stick with the W5500 schematic.
It does hint termination goes near the RJ45. It just feels a bit counter intuitive as the driver is located in the chip…
Thanks for your help - time spent here is better spent chasing corruption errors later on…
I think I’ve mostly nailed to points you highlight. This is just the polish…
My tracks are short - but its a template for other products that may not be so lucky…

### Reply 3 by Eugeny, 2017-05-19

jnewcomb:

> I’ll stick with the W5500 schematic.

You **MUST** stick to schematic of the chip you use, in this case W5500. That document contains design guidelines in general, which are good to implement to minimize *design issues*.

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Source: https://maker.wiznet.io/forum/12295