6

A shield usually makes a pretty good protector against electric field disturbances (half the story) but, unfortunately, makes a pretty poor protection against magnetically coupled noise (the other half of the story). Twisting the conductors in a pair mainly ensures that induced voltages (due to external magnetic disturbances) are equalized on both ...


3

I assume you want the fast rise time to appear at the load on the end of the long cables. Or you have a high di/dt load and you want to minimize the voltage dip at the load. In that case twisting the cables may help. The magnetic fields of close conductors carrying opposite currents will tend to cancel, reducing the inductance associated with the cabling. ...


2

There is no 'structure' between the pairs in the cable. What you can guarantee is that white/x will be twisted with x/white. Isolation between the pairs is enhanced by giving each pair a different number of twists per unit length. This avoids the stray electromagnetic coupling between pairs growing as the length grows.


2

Is it possible to create an ethernet bus line using only one twisted pair? Absolutely Yes. It won't be a bus as 10basex is, but will be point to point as most Ethernet implementations are today. Read up on IEEE Std 802.3bw-2015 100BASE-T1 –Automotive Environment This is a 100Mbps link over a single twisted pair. You can also get out to 1000Mbps using ...


2

1: that part should be OK. 2: They mean differential impedance. There are trace calculators that should let you achieve this -- or you can just figure that the on-PCB traces will be short. 3: I'm not sure if the right word is "possible" or "certainly". You can probably mitigate this a lot by dialing the data rate way down, but basically, all the parallel,...


2

The coupling between differential pairs is different when differential traces are run over a ground (or power) plane on a PCB than when they are run using unshielded twisted pair (UTP) wires. In the first case, assuming edge coupled traces on (or in) a PWB, each trace couples much more strongly to the ground plane than it does to the other trace. This is ...


2

Why do differential signal traces on a PCB require a reference plane to have a controlled impedance? They don't is the short and long answer. However, if you are wanting to fully utilize the space on your PCB for other components and other non-connected circuits you need to use ground planes to avoid upsetting the controlled impedance and avoiding ...


1

The whole network of resistors is the termination, not just the 120 ohm resistor. So the differential pair is terminated with approximately 109 ohms, which is close enough to 100 ohms. When both ends of a differential pair are terminated properly to 109 ohms, indeed the total termination is 54 ohms. If you use some pairs for power, they are not unused any ...


1

You can use RJ14/RJ25 connectors with 4P4C plug and any 2x2 UTP cable. These are smaller than RJ45. Note, that the original board has too much empty space and too many connectors. If all you need is one I2C line adapter, you can make PCB roughly the size of 6p6c jack footprint with all SMD parts (including I2C jack) on the other side of the board. You can ...


1

Do not install power cable next to communications cable. This is against the electrical code in most countries. In Australia, our Wiring Rules (AS 3000) specifically require power and communications cables to be physically separated, either by barriers or by distance. If the power cable is damaged, and shorts to the communications cable, then the ...


1

Since you already have return paths for both signal (green) and power (blue) inside the cable, you want to make sure that the shield does NOT carry any current. This would only unbalance your balanced pairs. Connect the shield to the circuit at only one end (the end that has the more solid earth connection), using it strictly as an electrostatic (E-field) ...


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