---
title: "[ICC] How should Ethernet Trans Center tab design circuits!"
url: "https://maker.wiznet.io/Alan/projects/%5Bicc%5D-how-should-ethernet-trans-center-tab-design-circuits%21/"
markdown_url: "https://maker.wiznet.io/Alan/projects/%5Bicc%5D-how-should-ethernet-trans-center-tab-design-circuits%21/md"
type: "WCC: WIZnet Created Content"
author: "Alan"
author_url: "https://maker.wiznet.io/Alan/"
original_author: "Alan"
published: "2023-03-08"
language: "en"
likes: 6
views: 149
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# [ICC] How should Ethernet Trans Center tab design circuits!

> A Brief Study on the Design of Ethernet Trans Center Tab

Original author: Alan

## Article

Hello! I'm Alan.
I made a topic because there was a circuit I wanted to study briefly while designing and debugging an Ethernet chip.

![](https://maker.wiznet.io/upload/ckeditor5/901043747%5F1678283179%2Epng)

This is the circuit.
W5300-ToE-Shield was designed, debugged, and discovered.

It can be seen that the CT of the Trans is fitted with a damping resistor (R31). This is a simple circuit used for many other companies' chips, not just for Wiznet's Ethernet chip.

It is usually short to 0 ohms or equipped with a 10-ohm resistor.

![](https://maker.wiznet.io/upload/ckeditor5/901043747%5F1678287777%2Ejpg)

In this design, it is equipped with 10 ohms for damping resistance.

![](https://maker.wiznet.io/upload/ckeditor5/901043747%5F1678287893%2Ejpg)

At first, I was very embarrassed because the link LED blinked every 1.5 seconds in this state.

It took a long time to find the cause. Of course I didn't think the reason was 10 ohms of damping resistance.

Here's what the waveform looks like.

![](https://maker.wiznet.io/upload/ckeditor5/901043747%5F1678288064%2Ejpg)

A waveform close to the trans was taken with the damping resistance mounted.

First, I set 3.3V as Offset, and V High is measured as 3V. As the voltage level moves so fast, even if the damping resistance is small, it seems to have a huge influence.

Of course, the device continues to try Link because Offset is not properly caught. From the waveform, it seems that Link Detection is performed every 1.5 seconds.

![](https://maker.wiznet.io/upload/ckeditor5/901043747%5F1678288404%2Ejpg)

Above is the waveform of Tx. The waveform is captured only when the link is attempted. And when it fails, take a 1.5 second break and try Link Detection again.

![](https://maker.wiznet.io/upload/ckeditor5/901043747%5F1678288637%2Ejpg)

This is the waveform in the short state.

![](https://maker.wiznet.io/upload/ckeditor5/901043747%5F1678288698%2Ejpg)

Of course, CT is output at 3.3V, and the data waveform is also 3.3V, so it seems that Offset is well established.

It works very well, too.

The W5300's Recommend circuit does not contain damping resistance. However, W5500, 5100S, and other chips may contain damping resistance.

I think it will be a good data to experiment and organize all of them. Next time, we will proceed with in-depth learning of the MDI circuit with such data.

---

Source: https://maker.wiznet.io/Alan/projects/%5Bicc%5D-how-should-ethernet-trans-center-tab-design-circuits%21/