---
title: "Transformer W5500"
url: "https://maker.wiznet.io/forum/13851"
markdown_url: "https://maker.wiznet.io/forum/13851/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "Gerry"
created: "2020-05-22T15:43:25+09:00"
last_activity: "2020-05-25T13:32:51+09:00"
language: "en"
views: 768
replies: 2
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Transformer W5500

## Question

Asked by Gerry on 2020-05-22 in Ethernet Chips.

Hello,

why are the resistors R16 & R17 needed, when using a transformer with the W5500 Chip?

[![Ethernet](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/c/cd7b3fc8d218bf2f79bc93f0be13346069e35459.png) Ethernet1152×648 38.8 KB](https://maker.wiznet.io/forum_uploads/wiznet/original/2X/c/cd7b3fc8d218bf2f79bc93f0be13346069e35459.png)

They are not necessary in other designs.

I would be glad, if someone could help me.

Regards,
Gerry

## Replies

### Reply 1 by bangbh, 2020-05-25

I think surge or extra energy can be reduced through those resistors but It doesn’t seem necessary.
Also, 82R of R6 and R7 can be replaced with 50ohm resistors.
But officially, only the recommended schematic can be guaranteed. Please understand this.
Because we can’t test all user’s schematics.

### Reply 2 by Gerry, 2020-05-25

Ok, thank you.

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Source: https://maker.wiznet.io/forum/13851