Typical Applications
There are a variety of circuits
that require protection from
the effects of ESD events.
Examples include: video,
mouse, keyboard, and I/O
computer ports; printer
and network ports; audio
components; communication
ports on business machines;
and other products which
rely on sensitive ICs.
Figures 4, 5 and 6 illustrate
the use of PulseGuard
®
suppressors in three typical
applications. Figure 4
shows protection of a
single communications
line. Figure 5 illustrates
protection of the data lines
of a USB port. Finally, Figure 6
details how a PulseGuard suppressor
can be configured to protect the driver/receiver
lines of an RS-232 port. Refer to the Selection
Guide for a wide variety of application
examples and a listing of recommended
Littelfuse products for each.
What is IEC 1000-4-2?
As previously mentioned, one of the
factors used to define the need for better
ESD protection is a more demanding standard
being used to determine the susceptibility of
equipment to damage by ESD. This important
specification is IEC 1000-4-2. Alternatively,
it can be referred to as EN61000-4-2.
Created by the International Electrotechnical
Commission (IEC), the 1000-4-2 specification
provides the definition of the ESD waveform,
energy levels, and the methodologies that are
used to test the ability of electronic equipment
to survive multiple, severe ESD events. The ESD
waveform and test severity levels (for contact
discharge) defined in 1000-4-2 are shown
in Figure 7. There are specifications for an
air-discharge test but contact discharge is the
preferred test methodology due to reproducibility
of the procedure.
Figure 7:
IEC 1000-4-2
Contact Discharge
Test Specifications
Time (ns)
100%
Rise time= 0.7 to 1.0ns
30ns 60ns
Voltage (V)
Severity
Level
1
2
3
4
Discharge
Voltage
2kV
4kV
6kV
8kV
Initial
Current
7.5A
15A
22.5A
30A
30ns
Current
4A
8A
12A
16A
60ns
Current
2A
4A
6A
8A
This test specification provides the means
for test engineers to inject repeatable test
pulses into the Equipment-Under-Test (EUT)
and evaluate it in terms of ESD survivability.
As Figure 7 illustrates, there are various
severity levels that can be used to define
the EUT’s immunity against ESD.
Regardless of the severity level chosen, the
ESD pulses are to be injected at locations
that are accessible to users during normal
operation and maintenance of the EUT. The
test is performed as a series of ten pulses,
applied in the polarity that the EUT is most
sensitive to. If the EUT is able to perform
without permanent damage or electronic
upset during and after the series of test
pulses, the EUT is said to have passed the
respective level of IEC 1000-4-2 testing.
Currently, electronic equipment manufacturers
are required to certify that their equipment
can survive testing to the IEC standard
if they are selling that equipment into the
European Union. The sale of electronic
equipment that cannot meet the 1000-4-2
testing is considered a prosecutable offense
in that market. Compliance is voluntary
in the United States at this time.
As the leader in circuit protection technology,
Littelfuse is introducing the connector
configuration and surface mount families
of PulseGuard ESD suppressors to assist
customers in complying with all severity
levels of IEC 1000-4-2 testing. By providing
full ESD suppression functionality and by
remaining electrically transparent to the
circuit that they are protecting, PulseGuard
ESD suppressors offer optimal protection
for your products.
