A box of rocks inside a connector?
Last time you heard from me I was exiting the Power world for Integrated Connector Magnetics, or ICM. These are the board side magnetic jacks loaded into switches and routers and other Ethernet communication devices that connect networks via RJ-45 cables. As I dive into the murky world of signal integrity, I have been further confounded by the addition of magnetics! Magnetic jacks provide for signal conditioning and isolation along with electromagnetic interference suppression.
Inside of these ICM products are many, many different components. They have names like toroid, ferrite, choke, transformer, capacitor, inductor and more. To make matters even more complicated, many components are connected via small copper strands, called magnet wire, in sizes as small as 36 AWG or 0.005 inches in diameter. That is roughly 5 times the diameter of the average human hair. Magnet wire and ferrites are combined using “winding” techniques into small subassemblies called either transformers or chokes. Now most of you are probably thinking of the Transformer movies or your local major league baseball teams (remember, I am from Chicago!), but I digress. These subassemblies are then inserted into the circuit path of the ICM connector and, voila! You have your box of rocks!
But wait, it gets even more complicated!
Think about sewing a button onto your shirt (I know all about this as my wife does not sew!). Preparing transformers and chokes is akin to sewing thread through a button. With one minor difference – the number of turns and twists on these wires in the windings has a HUGE impact on the signal integrity of the connector. The numbers of turns and twists affect things like common mode rejection, return loss and insertion loss, all of which are governed by an IEEE document. All this really means is that the industry is trying to make sure that when someone walks by your IT closet while talking on their cell phone, the cell phone signal does not “leak” through the RJ-45 connection and interfere with the constant gaggle of email in any large or small business. I am probably oversimplifying it, but in the end that is what my kids would understand. Don’t mess with my cell connection or my email!
There are literally millions upon millions of tiny little magnetic components out there in ICM connectors, most of which are hand wound, making it even more amazing to me that these products work as well as they do!
And it is about to get a whole lot tougher as the telecommunications industry works to keep up with demand for cloud computing and storage. People want more information and they want to move it around even faster. The vast majority of today’s ICM products are geared toward 1 gigabit Ethernet applications. But just around the corner is 10Gbe, and the industry still wants to use the RJ-45 since its low cost and field termination capability make it extremely attractive!
Of course with higher speeds, the work of the magnetics gets tougher. Moving to 10Gbe means that the magnetics are even more challenging to “tune” with the PHY chip (physical layer that manages the send and receive signals in Ethernet communications). Proper tuning of the magnetic components is required to ensure meeting IEEE standards for managing “noise” in these communication devices. Preventing unintended signals from disturbing your cellular communications and your internet experience is what ICM is all about. And it would be impossible without all of these tiny, toroids, ferrites, chokes, transformers, er, I mean magnetics! Who’d believe your internet reliability could be so controlled by a box of rocks?