Cable Ferrite Types: Are You Using The Correct One?

Most electronic gadgets incorporate wires in some form as an essential part of the assembly. These wires vary considerably as far as their appearances are concerned, and you will notice that some feature a cylindrical bead at the end. The inclusion of this bead is not just cosmetic; it serves a valuable function as well. Known as a cable ferrite bead, or more commonly, a choke, this is a passive device that eliminates EMI noise from a circuit in the form of heat. The bead also prevents your cable from sending signals except in the intended direction.

Application of the Right Ferrite Bead Matters: Here’s Why

The incorrect use of ferrite beads in a particular system design does more harm than good. For example, a device might experience unwanted resonance when the bead is combined with a decoupling capacitator for low-pass filtering, and the dc bias current dependency deteriorates the EMI suppression property of the ferrite. So, instead of selecting a random cable ferrite bead for your product, there are a few things you need to do:

·        Learn more about the noise issue affecting the circuit, including the noise sources.
·        Gauge the permissible trade-off for DC resistance and the required AC impedance.
·        Select the proper material behavior required, such as high loss at low frequencies.
·        Never assume that the ferrite bead is going to solve your EMI problems.
·        Just because a particular setup worked before doesn’t mean it will work again.
·        Know the impedance curve and other details from the component to be used.

Keep in mind that cable ferrite manufacturers use a wide range of materials, and you should review the frequency performance of each product to ensure it meets your requirements.

Categories of Ferrite Beads

Multiline Ferrites: The best part about this interference suppression element is that you can use it anywhere. In the first instance, the multiline ferrite works as a quadruple brushing choke, which has a high-level current rating (ideally 4A) and is current-compensated. Depending on the connection, the current or impedance can be increased. On the other hand, the suitable connection is capable of producing a double current-compensated broadband choke.

Ribbon Cable Ferrites and Flat Ferrites:  A technology that functions at a high-enough frequency follow certain rules. For example, two centimeters of ribbon cable can serve as an effective antenna under certain circumstances for emitting or coupling interference. Flat ferrites or ribbon cable ferrites help maintain limit values in situations where longer ribbon cable is required.

6-Hole Ferrite Beads: Usually known as UKW chokes, the standard 6-hole bead cables feature 2.5 windings of wire and are capable of tolerating prolonged currents without any saturation. In this case, manufacturers can attain effective HF interference directly on the board.

SMD Ferrites: Electromagnetic ferrites have undergone several changes due to the miniaturization trend. SMD ferrites allow conduction of currents, with the ferrite acting as a low-resistance brushing for the useful signal as well as a high loss resistance for the interference spectrum.

Ferrite Rings and Ferrite Sleeves: Unlike ferrites with nylon clamps or snap ferrites, ferrite rings or ferrite sleeves are positioned on the cable before the final assembly. They remain anchored through potting methods or heat-shrink tubing. Nowadays, all computer monitors use this solution. To maximize the effects of interference suppression, the inside diameter should match the cable diameter as closely as possible. Manufacturers can increase the impedance level along with inductive percentage by multiple bushings.

Cable ferrites are small components that play a big role in preventing interference among electronic devices. But manufacturers must pay attention to the kind of ferrite beads they are selecting because it can affect the overall performance.