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© KEMET Electronics Corporation • P.O. Box 5928 • Greenville, SC 29606 (864) 963-6300 • www.kemet.com

E5005_ESD-SR • 3/25/2015

One world. One KEMET

EMI Cores

ESD-SR Series Snap-on Cores for Round Cables

Overview

KEMET ESD-SR Series snap-on cores

are designed for use on round cable

and are available in a variety of sizes.

EMI cores are part of a family of passive

components which address the issues

of noise or electromagnetic interference

(EMI) in circuits or systems.

Benefits

• Snap-on convenience

• Split construction

• Temperature Index of 65°C

• Meets the requirements of UL94V-0

• CTI: Rank 0

• Broad range by simply adding turns

Applications

• Consumer electronics

EMI Core

5

EMI Cores

Ring Type

　There are two materials of ferrite, Ni-Zn series and Mn-Zn ser

ies. Ni-Zn series is

e

ive for kHz band range.

　Note that above

e band range i

s a reference only. Examination of

s

with actual instrument is necessary.

　As Mn-Zn series has lower resistance compared to Ni-Zn series,

make sure to provide

adequate insulation before use.

Characteristics and how to count turns

　Number of turns are counted by how many times the lead wire pa

sses through the inner

hole of the core. Do not count the number of lead wire winding

outside the core, as it results

　When desired performance can not be obtained just b

y 1 turn, impedance characteristics

value can be raised b

y increasing th

e turn. In this case, the

e frequency band should

be checked that it is in the desired range as adding turns resu

lts in lowering down the

Tips on EMI Core Usages

（Represe ntative Example：ESD-R-16C）

Fig.1

　How to count turns

Fig.2

　Relationship between impedance an

d turn counts

*Number of lead wire wound outside the core + 1

= Number of read wire passes through the inner

hole of the core

= Turn count

Mn-Zn series vs Ni-Zn series

｜Z｜-f Characteristics (representative example)

(measurement condition: measured with same-dimension ring core)

Fig.3

　

te

AM band range

FM band range

MnZn series core

NiZn series core

1000

100

10

1

0.01

0.1

1

10

100

1000

Resonance point changes to lower band

3T

2T

1T

Frequency (MHz)

Frequency (MHz)

10000

1

10

100

1000

1000

100

10

1

3T

2T

1T

Figure 1 – How to count turns

EMI Core

5

EMI Cores

Ring Type

　There are two materials of ferrite, Ni-Zn series and Mn-Zn ser

ies. Ni-Zn series is

e

ive for kHz band range.

　Note that above

e band range i

s a reference only. Examination of

s

with actual instrument is necessary.

　As Mn-Zn series has lower resistance compared to Ni-Zn series,

make sure to provide

adequate insulation before use.

Characteristics and how to count turns

　Number of turns are counted by how many times the lead wire pa

sses through the inner

hole of the core. Do not count the number of lead wire winding

outside the core, as it results

　When desired performance can not be obtained just b

y 1 turn, impedance characteristics

value can be raised b

y increasing th

e turn. In this case, the

e frequency band should

be checked that it is in the desired range as adding turns resu

lts in lowering down the

Tips on EMI Core Usages

（Represe ntative Example：ESD-R-16C）

Fig.1

　How to count turns

Fig.2

　Relationship between impedance an

d turn counts

*Number of lead wire wound outside the core + 1

= Number of read wire passes through the inner

hole of the core

= Turn count

Mn-Zn series vs Ni-Zn series

｜Z｜-f Characteristics (representative example)

(measurement condition: measured with same-dimension ring core)

Fig.3

　

te

AM band range

FM band range

MnZn series core

NiZn series core

1000

100

10

1

0.01

0.1

1

10

100

1000

Resonance point changes to lower band

3T

2T

1T

Frequency (MHz)

Frequency (MHz)

10000

1

10

100

1000

1000

100

10

1

3T

2T

1T

Figure 2 – Relationship between impedance and turn count.

(Representative example: ESD-R-16C)

EMI Core

5

EMI Cores

Ring Type

　There are two materials of ferrite, Ni-Zn series and Mn-Zn ser

ies. Ni-Zn series is

e

ive for kHz band range.

　Note that above

e band range i

s a reference only. Examination of

s

with actual instrument is necessary.

　As Mn-Zn series has lower resistance compared to Ni-Zn series,

make sure to provide

adequate insulation before use.

Characteristics and how to count turns

　Number of turns are counted by how many times the lead wire pa

sses through the inner

hole of the core. Do not count the number of lead wire winding

outside the core, as it results

　When desired performance can not be obtained just b

y 1 turn, impedance characteristics

value can be raised b

y increasing th

e turn. In this case, the

e frequency band should

be checked that it is in the desired range as adding turns resu

lts in lowering down the

Tips on EMI Core Usages

（Represe ntative Example：ESD-R-16C）

Fig.1

　How to count turns

Fig.2

　Relationship between impedance an

d turn counts

*Number of lead wire wound outside the core + 1

= Number of read wire passes through the inner

hole of the core

= Turn count

Mn-Zn series vs Ni-Zn series

｜Z｜-f Characteristics (representative example)

(measurement condition: measured with same-dimension ring core)

Fig.3

　

te

AM band range

FM band range

MnZn series core

NiZn series core

1000

100

10

1

0.01

0.1

1

10

100

1000

Resonance point changes to lower band

3T

2T

1T

Frequency (MHz)

Frequency (MHz)

10000

1

10

100

1000

1000

100

10

1

3T

2T

1T

Figure 3 – Effective band range of MnZn and NiZn ferrite core material.

(Representative example, measured with same-dimension ring core)

Turns and Impedance Characteristics

When the desired performance of an EMI core cannot be

obtained with a single pass through the core, the impedance

characteristics can be changed with multiple turns.

A turn is counted by the number of lead-wire windings which

pass through the inner hole of the core. Windings on the

outside of the core do not count. See Figure 1 for examples

of one, two, and three turns.

Adding turns will result in higher impedance while also

lowering the effective frequency range. See Figure 2 for an

example.

Core Material and Effective Frequency Range

There are two ferrite material options for KEMET

EMI Cores: Nickel Zinc (NiZn) and Manganese

Zinc (MnZn). Each core material has a different

resistance and effective frequency range. The MnZn

core material has a lower resistance compared to

the NiZn; therefore, adequate insulation is required

before use.

The NiZn core material is typically effective for

frequencies in the MHz band range such as the

FM-band, while the MnZn core material is typically

effective for the kHz band range such as the AM-

band. See Figure 3.

It is recommended to measure the actual frequency

range effectiveness in the target application.