I don't know how to wire RJ45 connector with magnetics - Page 1
Forum section: electronics / projects

author: sw_guy
author_rank: Regular Contributor
timestamp: February 09, 2024, 03:59:22 pm
content: First, yes, this is a duplicate. It seems that "nobody" reads the beginner section.There are a few variations of RJ45 connectors (with magnets). I am not sure how to connect P1 and P10. I can see that on some connectors P10 is connected to GND and P1 to GND thru 10nF capacitor, but internal wiring (=center tap) is not exactly the same way.Thanks in advance!sw guyEdit: magnets to magnetics

author: ataradov
author_rank: Super Contributor
timestamp: February 09, 2024, 04:41:53 pm
content: There are multiple ways to connect those center taps. It depends on the PHY you are using. You need to look in the datasheet and/or reference schematic for your PHY.

author: tooki
author_rank: Super Contributor
timestamp: February 09, 2024, 05:22:14 pm
content: Cross-posting because you didn’t get enough answers fast enough is generally not going to get you any more answers, but will annoy people — for the most part, it’s the same core of people reading and answering all the subforums. If you’re not getting answers, there may be something wrong with your question, like providing too little context or not showing what you’ve done already.Also, you need to be patient: getting miffed that you haven’t gotten enough responsesonly 26 hours after postingis ridiculous. Sometimes answers come quickly, sometimes it takes time.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 09, 2024, 05:34:13 pm
content: complaint as been made to a mod

author: sw_guy
author_rank: Regular Contributor
timestamp: February 09, 2024, 07:15:49 pm
content: Quote from: coromonadalix on February 09, 2024, 05:34:13 pm

author: pcprogrammer
author_rank: Super Contributor
timestamp: February 09, 2024, 07:38:31 pm
content: Quote from: ataradov on February 09, 2024, 04:41:53 pmThere is also something to do with POE in combination with the center tabs. Have you searched the net for any schematics where ehternet connectors with integrated magnetics are used?You might findthisinteresting to read.Also as a hint and understandable when English is not your native language, the word "magnets" in the thread title is incorrect and possibly misleading. You might want to change it to "How to connect RJ45 Jack with Integrated Magnetics".

author: selcuk
author_rank: Frequent Contributor
timestamp: February 09, 2024, 07:45:54 pm
content: As suggested, check out the ethernet transceiver's application notes. Some needs termination resistors as well. Connector datasheets don't include that information.

author: sw_guy
author_rank: Regular Contributor
timestamp: February 09, 2024, 08:23:22 pm
content: >Have you searched the net for any schematics where ehternet connectors with integrated magnetics are used?I have and I thought it was a quick search to find the answer but it turned out it wasn't. I have a couple of reference circuits but they do not have exactly the same internal wiring.>You might find this interesting to read.This was one of pages I found. But I did not get more information out of it.> word "magnets"My apologies. Typo corrected.>As suggested, check out the ethernet transceiver's application notes. Some needs termination resistors as well. Connector datasheets don't include that information.Ok, so if the answer is to follow PHY then the answer might be rather clear (or not). PHY datasheet was the first document I had and according to the datasheet, center taps (pins 4 and 5) are connected to GND thru 100nF capacitor. Since the magjack I have has an internal 100nF capacitor the same circuit can be made by connecting P10 to GND. And this is pretty much what I have found from other designs too.The attached image is the magjack used in the PHY's reference design.sw guy

author: ataradov
author_rank: Super Contributor
timestamp: February 09, 2024, 09:00:12 pm
content: The equivalent connections would be P1 to pins 4+5, and P10 to the ground.

author: sw_guy
author_rank: Regular Contributor
timestamp: February 09, 2024, 09:27:42 pm
content: >The equivalent connections would be P1 to pins 4+5, and P10 to the ground.Yes, and that is the initial conclusion I made as well. As per PHY doc, pins 4+5 goes to ground thru 10nF capacitor. Just the the setup is not the same: central taps are grounded first by internal 100nF capacitors and by 10nF external capacitor.sw guy

author: ataradov
author_rank: Super Contributor
timestamp: February 09, 2024, 09:34:25 pm
content: What is your PHY? What 10 nF capacitor you are talking about?

author: sw_guy
author_rank: Regular Contributor
timestamp: February 09, 2024, 11:39:08 pm
content: The PHY: BCM54210PEThe attached image is taken from the reference circuit. This one has 100nF capacitor (pins 4&5 to ground).I could make my life easier and order these:https://www.mouser.fi/ProductDetail/TE-Connectivity/5-2337992-8?qs=l4Gc20tDgJIqFEPxQvwM3w%3D%3Dwhich is a direct replacement to the MagJack-A70-112.sw guy

author: eb4fbz
author_rank: Regular Contributor
timestamp: February 10, 2024, 05:08:19 pm
content: For BCM54210PE (Voltage mode transceiver), P10 must be grounded and P1 left open.

author: sw_guy
author_rank: Regular Contributor
timestamp: February 10, 2024, 05:43:20 pm
content: Quote from: eb4fbz on February 10, 2024, 05:08:19 pmYes. I was right about writing that I got this now. Or... I get both of the topics now: first, I was not able to find an answer how to connect different RJ45 connectors because there is not such a question. The question is how the PHY needs a connector to be wired. And the second question: what is the equivalent wiring for the RJ45 connector I chose to use with the PHY in question. And that is: connecting P10 to ground so that center taps are grounded thru 100nF.This was definitely about learning something new. Again.Thanks all!sw guy