Series Caps in Rx-Path

Question

Hi there. According to all reference schematics referring W5500 there are series caps in RXP and RXN path. e.g. C9, C10 in [url]http://wizwiki.net/wiki/lib/exe/fetch.php?media=products:w5500:w5500-ref-rj45with20150406.pdf[/url] Are they mandatory for W5500? I have to make a design which has to be compatible to a coupling device plugged into a 100 BASE-TX link. The schematic could be said as this: W5500 === Device with caps === Switch The cable length from and to the device will not exceed 1.5 m and the caps within the coupling device are 4.7nF and cannot be changed. I already figured out that if I shorten the caps I’m able to establish a link with a few devices. For testing I have a Netgear FS108 and a FS108P, the last one contains PoE. A link is established with the 108P Switch but not with the 108 one. My circuit is not using PoE at all. If I double the caps within the coupling device (only allowed for testing purpose) there is a link, and data transfer, with both types of switches. So to sum up the question(s). Are the series caps mandatory? Can someone imagine of a way to increase compatibility to switches? Thanks in advance Skyfox

Matthew · Answer

Hello. I am Matthew, Wiznet researcher. Sorry for late reply first. Are the series caps mandatory? → Series CAP is mandatory. (C9, C10) Can someone imagine of a way to increase compatibility to switches? → There is not enough information to understand how 4.7nF is connected and the content of the post. If you show me the schematic or configuration diagram (more detail), I think I might be able to answer how to improve the compatibility of the switch. Thank you.