1812J1000682MCTE03 Syfer, 1812J1000682MCTE03 Datasheet - Page 3

• Manufacturer Part Number: 1812J1000682MCTE03
• Description: EMI Filters 1812 .0068uF 100V C0G 20% X2Y Filter
• Manufacturer: Syfer

Specifications of 1812J1000682MCTE03

• Product Category: EMI Filters
• Rohs: yes

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The use of electronic equipment is ever-increasing,
with greater likelihood of interference from other
pieces of equipment. Added to this, circuits with lower
power levels that are more easily disturbed means that
equipment is increasingly in need of protection from EMI
(electromagnetic interference). To meet legislation such as
the EU Directive on EMC, in addition to other international
regulations such as FCC, EMI filtering is now an essential
element of equipment design. Introducing screening
measures, eg to the case or cables, may suffice in many
instances, but some form of low-pass filtering will often be
required.
Faraday Cage
The ideal way of protecting a piece of equipment or circuit
from EMI is to totally enclose it in a metal (or conductive)
box. This screened enclosure is called a ‘Faraday Cage’.
Radiated interference is thus prevented from adversely
affecting it (Fig 1).
Input/output cabling
In reality however, most pieces of equipment require
input and/or output connections, perhaps power cables
or signal and control lines. The cables providing these
connections can act as antennae, able to pick up
interference and also to radiate it (Fig 2). Any cable or
wire going in through the equipment case can introduce
electrical noise, and also radiate it internally onto other
wires and circuits. Similarly, it can provide a path to the
outside from any noise generated internally, which can
also then be radiated and may in turn adversely affect
other equipment.
1. Interference can enter a piece of equipment directly
2. Radiated interference can travel directly to the
3. Interference can exit an EMI source via a cable,
4. Interference can be radiated from an EMI source
Filter location - panel mount filters
To prevent interference entering or leaving a piece of
equipment, feedthrough EMI filters can be mounted in
the wall of a shielded case. Any incoming or outgoing
cables would then pass through the filters. Power or
wanted signals pass through the filters unaffected, whilst
higher frequency interference is removed. While the
screened case protects against radiated interference, the
feedthrough filters protect against conducted interference.
The integrity of the equipment is thus assured (Fig 3).
Filter location - surface mount filters
Where there is no suitable bulkhead for mounting the
filters, pcb types can be used (Fig 4). While this can be
an effective method of filtering, it should be noted that in
general the insertion loss performance can be reduced at
higher frequencies, unless additional screening measures
are taken.
Good design practices such as short tracks, short
connections, close proximity to input and good grounding
will help improve insertion loss performance.
The need for EMI filters
through the cabling (conducted interference).
affected equipment.
subsequently to be radiated from the cable and to the
affected equipment.
and then picked up by a cable entering the affected
equipment.
Conducted interference
Faraday Cage
Faraday Cage protects against
radiated interference
Modes of propagation of EMI
Feedthrough filters remove conducted interference
and provide ultimate performance
Surface mount filters remove conducted interference,
performance reduced due to radiated interference
feedthrough filters or
Conducted interference
EMI source
Panel mounting
filter connector
2
input
4
Circuit
interference
Radiated
1
interference
Radiated
Pcb mounting filters
3
Radiated
interference
Equipment
affected by
output
EMI
Fig 1
Fig 2
Fig 3
Fig 4
Conducted interference
Interference transmitted along a conductor/cable.
Protection is provided by a series component. If a
feedthrough filter is used to remove conducted interference,
and mounted in the wall of a shielded compartment, it
provides effective filtering while maintaining the screening
integrity. It should be noted that the filter will reduce both
emissions and susceptibility.
Cut-off frequency/3dB point
The frequency at which filters start to become effective - is
generally taken to be at the 3dB point of the attenuation
curve. Anything on the line below this frequency will be
unaffected. The higher the capacitance of the filter the lower
the cut-off, and vice versa. It will also vary depending on
source and load impedances.
EMC
ElectroMagnetic compatibility. A situation wherein two pieces
of electrical or electronic equipment are able to function in
the same environment without adversely affecting, or being
affected by, each other.
EMI
ElectroMagnetic interference. A broad term covering a wide
range of electrical disturbances, natural and man-made, from
dc to GHz frequencies and beyond. Sources of disturbance
may include radar transmitters, motors, computer clocks,
lightning, electrostatic discharge and many other phenomena.
Emissions
Signals, unwanted (interference) or otherwise from a piece of
equipment.
ESD
Electrostatic discharge, which can result in damage through
excessive voltage spikes. We can offer assistance on whether
our products can meet specific ESD test requirements.
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 voltages
appearing across the line immediately beyond the point of
insertion, before and after insertion. As measured herein,
insertion loss is represented as the ratio of input voltage
required to obtain constant output voltage, with and without
the component, in the specified 50W system. This ratio is
expressed in decibels (dB) as follows:
Where:
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.
Low-pass filter
A filter that lets through dc and low frequency signals, while
attenuating (unwanted) high frequency noise.
Insertion loss = 20 log E
E
with the component in the circuit.
E
with the component not in the circuit.
1
2
= The output voltage of the signal generator
= The output voltage of the signal generator
E
1
2
Panel mount filter
A panel mounted filter that will pass the signal from one side
of the wall of a shielded box (or ‘Faraday Cage’) to the other
(it feeds the signal through the panel). For effective operation,
the filter input and output should be screened from each
other, ie there should ideally be no apertures in the panel.
Radiated interference
Interference transmitted in free air. Protection is provided by
shielding.
Surface mount filter
A filter that is suitable for surface mounting on PCBs. It
offers improved filtering compared to standard MLCCs, ease
of assembly and savings on board space compared to a
combination of descreet filter elements. Filter performance at
higher frequencies is reduced compared to panel mount types,
unless additional shielding measures are taken (see page 10).
Susceptibility
The extent to which a piece of equipment is vulnerable to
interference emitted from another piece of equipment.
Working voltage
Continuous operating voltage. This can potentially be across
the entire operating temperature range.
X2Y filter
Integrated passive component with extremely low self
inductance for filtering and de-coupling.
For filtering applications:
For de-coupling applications:
Panel mounting
feedthrough filters
Explanation of common terms
RETURN
SIGNAL
A
B
C1
C1
C1
C1
C2
A
B
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