Ferrite EMI Cable Cores
About Laird
Laird is a global technology business focused on enabling wireless communication
and smart systems, and providing components and systems that protect
electronics. Laird operates through two divisions, Wireless Systems and
Performance Materials. Wireless Systems solutions include antenna systems,
embedded wireless modules, telematics products and wireless automation and
control solutions. Performance Materials solutions include electromagnetic
interference shielding, thermal management and signal integrity products. As a
leader in the design, supply and support of innovative technology, our products
allow people, organisations, machines and applications to connect effectively,
helping to build a world where smart technology transforms the way of life.
Custom products are supplied to major sectors of the electronics industry including
the handset, telecommunications, IT, automotive, public safety, consumer,
medical, rail, mining and industrial markets. Providing value and differentiation to
our customers through innovation, reliable fulfilment and speed, Laird PLC is listed
and headquartered in London, and employs over 9,000 people in more than 58
facilities located in 18 countries.
TABLE OF CONTENTS
Ferrite Material Impedance Comparison ................................................ 3
Design & Selection “Rules of Thumb” ..................................................... 3
High Frequency (HFB-) Cylindrical Cores ................................................ 4
High Frequency (HFA-) Split, Snap-On Cores .......................................... 5
Broadband (28B-) Cylindrical Cores ....................................................... 6
Broadband (28A-) Split, Snap-On Cores ................................................. 9
Low Frequency (LFB-) Cylindrical Cores ................................................ 15
Broadband (28R) Ribbon & Flex Cable Cores ....................................... 16
Broadband (28S) Split Ribbon & Flex Cable Cores ............................... 20
Ferrite EMI Disks & Plates .................................................................... 26
Ferrite Plates for Wireless Charging ...................................................... 27
Flexible Ferrite Sheets ........................................................................... 29
Sample Kit Lists .................................................................................... 32
Pb
All parts listed in this catalog are lead free and RoHS compliant.
NOTICE
Laird’s products or subcomponents are not specifically designed or tested by Laird for
use in any medical applications, surgical applications, medical device manufacturing, or
any similar procedure or process requiring approval, testing, or certification by the United
States food and drug administration or other similar Governmental entity. Applications
with unusual environmental requirements such as military, medical, life-support or
Life-sustaining equipment are specifically not recommended without additional testing
for such application.
FERRITE EMI CABLE CORES
FERRITE MATERIAL COMPARISON
LF, 28 & HF MATERIAL IMPEDANCE VS FREQUENCY (300 KHz - 2 GHz)
Impedance Materials for Cable & Wiring Harness Cores
HF
LF Low Frequency
28 Broadband High Performance
28
Impedance (Z) in Ohms (Ω)
HF High Frequency
LF
0.3
0.5
1
5
10
50
100
1000
2000
Frequency (MHz)
DESIGN & SELECTION “RULES OF THUMB”
SELECT THE APPROPRIATE FERRITE MATERIAL
For the EMI frequency range to be attenuated, refer to cable core material impedance vs.frequency chart above.
FERRITE MATERIAL COMPOSITION AFFECTS CORE PERFORMANCE MOST
High-performance material is best. Cheap, low-performance materials require the use of larger, heavier cores.
SHAPE (DESIGN) AND MASS OF THE FERRITE CORE SIGNIFICANTLY AFFECT IMPEDANCE
DON’T OVER SIZE
Use high-performance ferrite material and select the smallest core that will do the job. High-performance material
allows the use of smaller, lighter and lower cost cores.
SELECT A FERRITE CORE THAT FITS OVER THE CABLE’S OUTSIDE DIMENSIONS
Core should slide easily over the cable during installation.
WHEN POSSIBLE, INSTALL A CABLE CORE OVER WIRES IN A COMMON MODE CONFIGURATION
(Out and back lines inside the same ferrite cable core). A differential cable pair inside the same core will make the ferrite core a
common mode choke that is not susceptible to saturation from very high currents.
INSTALL THE FERRITE CORE NEAR THE NOISE SOURCE
ADDITIONAL TURNS THROUGH A CORE WILL PROVIDE MULTIPLE AMOUNTS OF PEAK IMPEDANCE
Example: Two wire turns provide four times the impedance of one turn (pass through) the ferrite core. Also, with each added turn,
the peak impedance shifts to a slightly lower frequency.
TWO-PIECE SPLIT CORES ARE AVAILABLE
One-piece cylindrical or flat ribbon ferrite core shapes are usually preferable, but split cores can be used in applications where
cores cannot slide over cable ends and connectors. Some split cores are available with snap-on plastic cases or metal clips.
SIDE-BY-SIDE IMPEDANCE TESTING OF FERRITE CORES IS THE BEST WAY TO COMPARE
PERFORMANCE OF DIFFERENT CORES
Ferrite core impedance measurement equipment and test methods are not standardized in the industry.
Every ferrite company has their own test methods. Catalog (web site) impedance data cannot be accurately compared.
Optimized, high-performance, low-cost custom part designs are available.
www.laird.com
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