FERRITE MATERIAL COMPARISON

LF, 8, HF Material Impedance vs Frequency ( 00 KHz -  GHz )

Frequency ( MHz )

0.3

0.5

1

5

10

50

100

500

1000

2000

Impedance Materials for Cable & Wiring Harness Cores

LF Low Frequency

8 Broadband High Performance

HF High Frequency

LF

8

HF

· 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 4 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.

DESIGN & SELECTION “RULES OF THUMB”

Optimized, high performance, low cost custom part designs are available.