0

I am working with fast Ethernet. My question is that we are using only two pairs in 100 Mbps.

How will I terminate pin 4 and 5 and pin 7 and 8?

Can I separately terminate magnetic center tap with a 75 Ω resistor and capacitor and RJ45 pins with a 75 Ω resistor and capacitor?

Or do I need to terminate magnetic center tap and RJ45 pins (4, 5 & 7, 8) together with a 75 Ω resistor for each pin and one capacitor? What are the pro and cons of both termination styles?

ocrdu
  • 9,195
  • 22
  • 32
  • 42
Manish Synergy
  • 1
  • See: https://electronics.stackexchange.com/questions/244559/different-recommendations-for-ethernet-front-end-terminaton?rq=1 – Tim Williams Jul 02 '22 at 05:19
  • Manish Synergy - Hi, You posted 2 "answers" using the entry box at the bottom of the page labeled "Your Answer". However they were not answers and have been deleted. You were asking some kind of clarification question, but they were unclear what you were referring to, so I could not convert them into a useful comment :( Please write clear comments requesting clarification. (a) Stack Exchange is different from typical forums, so please read the [tour] and the [help] for the main site rules. (b) There is also an FAQ. – SamGibson Jul 02 '22 at 11:27
  • (cont'd) (c) This article explains about comments and how to use them. (d) You must not add new information or ask clarification questions as an answer here on SE. It breaks the whole Q&A approach and may cause future problems for you, when the "non-answers" get deleted. Perhaps you wanted to include an image in a comment? If so, the technique explained here should be used. Note that the draft answer (or question) must not be submitted. It is used only to upload the image and is then discarded. – SamGibson Jul 02 '22 at 11:28

2 Answers2

0

According to this 10/100Base-T magnetics datasheet, each unused pair should be connected together and connected to ground with 75R through a 1000pF cap. There is no reason to connect these pairs to magnetics as these magnetics typically only support two pairs.

Diagram from datasheet: enter image description here

DoxyLover
  • 8,090
  • 1
  • 19
  • 24
0

Just don't

You don't need to terminate them. In fact there plenty of fast ethernet devices out there with only 4 gold fingers in the RJ45 socket.

If you need to use them for POE that's a different matter.

Jasen Слава Україні
  • 33,738
  • 1
  • 33
  • 70