What You Should Know When Selecting Ethernet Magnetics

All Ethernet equipment involves magnetics, meaning that it is not optional. Magnetics help protect against transmission failure. Some unwanted signals can be picked up from electromagnetic interference (EMI) either from the cable or subtle mismatches in impedance.

Here are details to remember when selecting Ethernet magnetics:

Ethernet Components A transformer has fixed attributes for inductance value, but there are various solutions for different applications. A discrete magnetics transformer with modules costs less and works well with high volume applications. Integrated Connector Modules (ICMs) serve as higher end alternatives that are appropriate for quick and easy designs. ICMs have a universal appeal since they integrate with a majority of systems, while maximizing space, increase reliability and reduce the number of components.

PHY Chips By looking up the PHY chip in your design, you can learn the manufacturer's recommendations they've done working with their own chip. Comparing transformer modules helps create a clear picture of the performance of individual components.

Comparing Magnetics The key to selecting a discrete LAN magnetics module comes down to reviewing PHY chip information, aside from comparing various performance values, such as the following:

1. Common mode rejection figures
2. Common mode choke for more filtering
3. Amount of transmission and reception crosstalk
4. Check insertion loss at various frequencies to gauge energy waste
5. Operating temperatures of modules
6. ICMS as well as discrete magnetics modules provide designs that use the proper current for PoE and PoE+ designs

ICMs are usually the most reliable options when selecting LAN magnetics. Decide if a single or double row of modules works best for your system. Due to magnetics being smaller and closer together in ICMs, there is unintended crosstalk that can can be minimized. It helps to choose a selector with sufficient shielding to reduce crosstalk. Additionally, Power over Ethernet (PoE) affects performance and isolation, due to higher currents.