W5500 pull-down and pull-up resistors


I am thrilled about the new W5500, the programming seems to be much cleaner than on the W5200 and it will me much easier for DIY production, too.

I have a question about the different reserved pins though of the W5500 (23, 38, 39, 40, 41, 42) which need to be pulled down and the mode selection pins (43, 44, 45) and the invert-logic comm pins (32, 37) which I will select and therefore need to pull-up.

In the reference schematic, each of those pins has its own pull-down or pull-up resistor.

In the manual however, it is written that each pin has an “internal bias after reset”. What is this “internal bias after reset”. Is it an internal pull-down or pull-up resistor. If yes, why has the reference schematic additional pull-down and pull-up resistors on these pins?

Can I safely tie the reserved pins directly to GND without an external pull-down resistor to lower the BOM?


Hi, ventosus.

We added pull-up and pull-down resistors for stability, ESD test and etc.
We recommend to add external pull-up, down resistors.

Also, refer to W5500 datasheet chapter 5.3(DC character).
We guarantee that range so, it’s up to you.

WIZnet :smiley: .