New hermetically sealed
panel mount filters
Introduction
Syfer Technology Ltd manufactures quality
multilayer ceramic components supplied to a
worldwide customer base.
Customers utilise Syfer’s components in all types
of applications including telecoms, industrial,
automotive, military, aerospace, space and medical.
Syfer EMI Filters provide high levels of insertion
loss performance in compact case sizes designed
for easy installation.
The SL range of ceramic based filters represents
an extension to our exciting SF range of filters
with the added features of hermetic construction,
wound coil inductors and iron powder cores for
improved high current performance.
Additionally, the range also includes a
selection of filters designed and tested to
meet the requirements of WE772 / DEF-STAN.
59-45/90/013.
Other products in Syfer’s EMI component range
include: surface mount feedthrough capacitors
and filters, EMI power filters, X2Y integrated
passive components and LTCC multi element high
frequency filters.
Syfer is a world class manufacturer of surface
mount and radial leaded ceramic capacitors,
including safety and surge protection devices.
Syfer is also a leading supplier of discoidal
and planar ceramic capacitors to the EMI filter
industry.
syfer.com
Contents
Syfer -
EMI Filters
New Panel Mount ranges
General introduction
- Factors affecting insertion loss and electrical configuration
- Choice of ceramic dielectric material
- Technical notes
- Installation and case styles
EMI filters
- C Filters
- L-C and C-L Filters
- Pi Filters
- WE772 C-L and Pi Filters
4
5
6
7
8
9
10
11
Ordering information
SLA
Case
style
SLA
SLO
SLP
SLR
SLS
SLT
J
Rated
Current (A)
A = 0.3
B = 0.45
C = 0.5
D=1
E=3
F=5
G=8
H = 10
J = 15
K = 20
L = 32
M = 63
N = 100
P=2
Q=4
C
Electrical
configuration
C = C section
L = L-C section
H = C-L section
P = Pi section
300
Voltage
080 = 80Vdc
100 = 100Vdc
150 = 150Vdc
200 = 200Vdc
300 = 300Vdc
450 = 450Vdc
0204
Capacitance in
picofarads (pF)
First digit is 0. Second and
third digits are significant
figures of capacitance
code. The fourth digit is
number of zeros following
Examples:
0153 = 15nF
0204 = 200nF
0285 = 2.8µF
P
Capacitance
tolerance
P = -0 +100%
(Standard)
X
Dielectric
C = C0G/NP0
X = X7R
1
Class
1 = STD
W = WE772
R = 4M7
resistor
L = WE772 +
4M7 resisitor
M = Metric
thread
Other tolerances
may be available.
Please refer to
factory.
Notes: Ordering code can have up to 4 additional digits on the end to denote special requirements.
All supplied with nuts and washers.
See page 7 for case styles.
For more information on WE772 specification filters see page 11.
For more information on 4M7 resistor option see page 6.
Factors affecting insertion loss
Insertion loss
At a given frequency, the insertion loss of a feed though
suppression capacitor or filter connected into a given
transmission system is defined as the ratio of output voltages
appearing across the line immediately beyond the point of
filtering, before and after insertion of the filter. As measured
herein, insertion loss is represented as the ratio of output
voltage measured with a constant input voltage, with and
without the component, in the specified 50W
system. This
ratio is expressed in decibels (dB) as follows:
E
Insertion loss = 20 log
1
E
2
Where:
E
1
= The output voltage of the signal generator with the
component in the circuit.
E
2
= The output voltage of the signal generator with the
component not in the circuit.
When testing is conducted with a network/spectrum analyzer,
the equipment usually maintains a constant output voltage
and can be set to record the output to input voltage ratio in
decibels.
The insertion loss performance is used to aid filter
selection by showing signal attenuation at any given
frequency. However, it can only ever be a guide as
actual performance in service will vary depending on
the overall circuit characteristics.
Insertion loss is determined by:
l
Electrical configuration
l
Source/load impedances
l
The load current (which can cause ferrite saturation)
l
Ceramic dielectric materials. The capacitance change will be
affected by applied voltage, temperature and the age of the part
l
Earthing impedance
l
Shielding integrity
Electrical configuration
A number of different electrical configurations are available
in feedthrough filters, including the common types shown
below. A single element filter (a capacitor or an inductor)
theoretically provides an insertion loss characteristic of 20dB
per decade, a dual element filter (capacitor/inductor) 40dB
per decade whilst a triple element filter (Pi or T configuration)
theoretically yields 60dB per decade. In practise, the insertion
loss curves do not exactly match the predictions, and the data
sheets should be consulted for the realistic figure. The choice
of electrical configuration is made primarily on the source and
load impedances and may also be influenced by the level of
attenuation required at various frequencies.
C filter
This is a feedthrough capacitor with low self inductance. It
shunts high frequency noise to ground and is suitable for use
with a high impedance source and load.
L-C filter
This is a feedthrough filter with an inductive element in
combination with a capacitor. It is commonly used in a circuit
with a low impedance source and a high impedance load
(or vice versa). The inductive element should face the low
impedance but can be fitted either end of the filter.
Pi filter
This is a feedthrough filter with 2 capacitors and an inductive
element between them. Ideally, it should be used where both
source and load impedances are high.
T filter
This is a feedthrough filter with 2 series inductive elements
separated by one feedthrough capacitor. It is suitable for use
where both source and load impedances are low.
C
L-C
C-L
Load current
For filters which include ferrite inductors, the insertion loss
under load current may be less than that with no load. This
is because the ferrite material saturates with current. The
reduction in insertion loss depends on the current and the
characteristics of the particular ferrite material. In extreme
cases the ferrite will become ineffective and insertion loss will
appear to be the same as for a C filter. For further information
contact the Sales Office.
Attenuation curve
Insertion loss is often represented in graphical form. Example
below.
0
-10
Pi
T
Source and load impedances
Insertion loss figures are normally published for a 50W
source
and 50W load circuit. In practise the impedance values will
probably be very different, which could result in either an
increase or decrease in insertion loss. The electrical configuration
of the filter (the capacitor/inductor combination) should be
chosen to optimise the filter performance for that particular
source/load impedance situation. An estimate of insertion loss
for source and load impedances other than 50W can be supplied.
Please contact our Sales Office.
Insertion Loss (dB)
-20
-30
-40
-50
-60
-70
-80
0.3
1
10
100
1000 3000
4
Frequency (MHz)
Choice of ceramic dielectric material
When choosing a filter, it is important to be aware of the
different performance characteristics that may be available
from different categories of ceramic materials employed in
their capacitors. Generally, stability of dielectric constant
(and therefore filter capacitance value), with respect to some
operational and environmental parameters, deteriorates with
increasing dielectric constant. Specific factors which affect
C0G/NP0
Most parameters for materials in this dielectric classification
are relatively unaffected by temperature, voltage, frequency
or time. Stabilities are measured in terms of parts per million
but dielectric constants are relatively low (10 to 100).
X7R
This is a classification for materials which are relatively stable
with respect to temperature, voltage, frequency and time.
Typical dielectric constants would be of the order 2,000 to
4,000, enabling the achievement of far higher capacitance
values for a given size of capacitor than can be gained from
C0G/NP0 materials.
Summary of Ceramic Dielectric Characteristics
dielectric constant are temperature, voltage, frequency and
time (ageing).
The three main classifications of ceramic dielectric employed
in the manufacture of EMI filters are generally referred to as
ultra stable (C0G/NP0), stable (X7R) and general purpose
(Z5U, Y5V or X7W).
If the voltage coefficient (Vc) is critical, Syfer are also able
to offer parts with BX (2X1) and BZ (2C1) Vc characteristics.
Refer to the factory for further details.
Z5U/Y5V/X7W
These are classifications for materials which are relatively
unstable with respect to temperature, voltage, frequency and
time. Whilst typical dielectric constants may be of the order
5,000 to 25,000, operating temperature ranges are severely
restricted.
A summary of the specifications of these materials follows.
Please note that Syfer uses only the higher performance C0G/
NP0 and X7R in its ceramic filter ranges.
C0G/NP0
EIA dielectric classification
Rated temperature range
Maximum capacitance
change over temperature
range (no voltage applied)
Ageing characteristics
Ultra stable
-55ºC to +125ºC
0 ±30 ppm/°C
Zero
X7R
Stable
-55ºC to +125ºC
±15%
1% per time
decade
Z5U
Y5V
General purpose
X7W
-10ºC to
+85ºC
+22-56%
6% per time
decade
-30ºC to
+85ºC
+22-56%
6% per time
decade
-55ºC to
+125ºC
+40-90%
6% per time
decade
Spread of capacitance values
The capacitance of a ceramic capacitor can change as a result of a change in temperature, applied voltage and age. Please note
that this potential change can lead to a significant drop in filtering performance.
Example
Consider the typical
performance of 5,000pF
filter capacitors, offered
in standard dielectric
classifications, operating at
a voltage of 100Vdc at 85°C,
at an age of 10,000 hours.
The final capacitance value
can fall within the range
of values (see chart to the
right), taking into account the
ageing process and effects of
temperature and voltage as
shown in the chart above.
negligible
change
5750pF
to
3500pF
6100pF
to
1000pF
6100pF
to
500pF
8540pF
to
250pF
9000pF
8000pF
7000pF
6000pF
5000pF
4000pF
3000pF
2000pF
1000pF
0pF
Nominal
Syfer only uses
these two
dielectrics
C0G/NP0
X7R
Z5U
Y5V
X7W
It is clear that the capacitance can change as a result of an increase (or decrease) in temperature, applied voltage and as a result
of ageing. If the capacitance has reduced, so too will the insertion loss performance.
All parts in this catalogue are X7R. C0G/NP0 are available on request for lower capacitance values.
5
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