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Application note
IEC 61000-4-2 standard testing
Introduction
This Application note is addressed to technical engineers and designers to explain how
STMicroelectronics protection devices are tested according to IEC 61000-4-2 standard.
This standard, describing testing and measurements techniques for electrostatic discharge
immunity, is dedicated to electrical and electronic equipment, and the way to apply it to
standalone electronics components may not be obvious.
Market environment
The IEC 61000-4-2 standard is commonly used to certify equipment such as mobile phones,
computers and any sensitive electronic equipment. Each of these devices has to be
protected against electrostatic discharges using components able to clamp and resist the
high voltages generated and defined by each standard level. The robustness of these
devices has to be checked and guaranteed.
Frequently asked questions
This document provides responses to the following:
June 2011
1.
Contact discharge or air discharge method?
2.
What about the IEC 61000-4-2 test bench?
3.
How do we test ESD in air discharge?
4.
How do we test ESD in contact discharge?
5.
How do we measure the clamping voltage?
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Contact discharge or air discharge?
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Contact discharge or air discharge?
According to the standard, contact discharge is the preferred test method. Air discharge
shall be used when contact discharge cannot be applied. Contact discharge is more
dedicated to conductive surfaces and air discharge to insulating surfaces. In case of air
discharge, the current level and rise time are less reproducible and more related to
environmental conditions (humidity, speed of the tip approach etc.).
However, STMicroelectronics protection devices are always specified according to the two
test methods, and the specified levels are most of the time the maximum standard levels.
That is to say 8 kV for contact discharge and 15 kV for air discharge (level 4 of the standard).
Note:
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The clamping voltage waveforms of our protection devices given in the datasheets are
measured at 8kV in contact discharge. This test condition gives the worst case clamping
voltage response because the rate of rise of the current gets its highest value (around
45 A/ns). (See Section 5: Clamping voltage measurement.)
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Test benches
2
Test benches
2.1
IEC 61000-4-2 test bench
Figure 1 shows the test bench recommended by IEC 61000-4-2 standard for ungrounded
equipment (mobile phones for example). This is the setup we adapted for our standalone
protection devices.
Figure 1.
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,(& IEC 61000-4-2 ed.2.0 “Copyright © 2008 IEC Geneva, Switzerland.www.iec.ch”
a.
STMicroelectronics thanks the International Electrotechnical Commission (IEC) for permission to reproduce Information from its International Standard IEC 61000-4-2 ed.2.0 (2008).
All such extracts are copyright of IEC, Geneva, Switzerland. All rights reserved. Further information on
the IEC is available from www.iec.ch. IEC has no responsibility for the placement and context in which
the extracts and contents are reproduced by STMicroelectronics, nor is IEC in any way responsible for
the other content or accuracy therein.
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Test benches
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STMicroelectronics test bench
STMicroelectronics test bench is described in Figure 2. All the dimensions (height,
materials, insulator thickness etc.) and ground connections are in accordance with the
standard (Figure 1).
The ESD gun is mounted on a stand with a slide arm in order to move it up to the device
under test especially during air discharge conditions.
Figure 2.
ESD test bench for STMicroelectronics protection devices
Horizontal coupling plane
(1.6 m x 0.8 m)
DUT GND
470 kΩ
Protective conductor
Insulating support
DUT
470 kΩ
470 kΩ
DUT PCB
470 kΩ
Non conducting table
ESD gun power supply
Ground reference plane
ESD Generator NSG438 TESEQ
ESD IEC6100-4-2 environment ESS-801 NOISEKEN
Our device is soldered on a dedicated PCB as shown in Figure 3. A 2 mm female banana
plug is connected to the ground plane of the PCB. This plug, through the bleeder resistors (2
x 470 kΩ), links the horizontal coupling plane to the PCB ground plane.
A rounded discharge tip is connected to the pin to test. Depending on the device, one or
more tips can exist. These tips are soldered on the bottom side of the PCB such that they
act as a shield for the clamping voltage measurement by means of the SMA plugs added in
the top side of the PCB.
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Test benches
Figure 3.
Test PCB example
SMA plugs for clamping
voltage measurements
Device
under
test
Device under test
GND connection
Top side
Discharge tips
Bottom
side
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Air discharge test
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Air discharge test
The rounded ESD gun dedicated to air test is used. The voltage generator is set to the
desired level and the ESD gun moved with the slide arm towards the PCB probe tip until a
spark appears and then further until the ESD gun tip touches the PCB discharge tip. This
action is repeated ten times minimum, in positive and negative polarities.
4
Contact discharge test
The sharp tip ESD gun dedicated to contact test is used. Contact is maintained with the
PCB discharge tip by locking the slide arm. The generator is set to the desired voltage and
ten discharges minimum are applied in positive and negative polarities to the device under
test.
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5
Clamping voltage measurement
Clamping voltage measurement
As we say in Section 1: Contact discharge or air discharge?, the clamping voltage
measurement is done in contact mode at ±8 kV. The ground return of the ESD gun is
connected directly to the GND test PCB, as well as the reference of the oscilloscope.
A 3 GHz analog bandwidth oscilloscope is used (2 GHz minimum is recommended by the
standard). Its sample rate is 20 giga samples per second and the time base is set to
20 ns/div. The vertical amplifier input impedance is set to 50 Ω.
A 50 Ω coaxial cable is connected to the SMA where the clamping voltage is measured
(Figure 3). Depending on the device and the test conditions, the clamping voltage can vary
between several volts up to around two hundred volts. So attenuators are inserted at the
end of the cable at the channel oscilloscope input. Two -20 dB attenuators in series give an
attenuation ratio of 100.
A clamping voltage waveform example is shown in Figure 4. On the waveform, we find the
typical clamping voltage at three different times after the beginning of the surge: t = 30 ns,
t = 60 ns and t = 100 ns. The typical peak voltage is also noted.
According to the JESD210 Jedec standard, a limiting resistor can be added in series with
the measurement cable. In this case, its value is specified.
Figure 4.
Clamping voltage waveform example
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Conclusion
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Conclusion
This document describes how STMicroelectronics protection and filtering devices are tested
to guarantee their capability to withstand the IEC 61000-4-2 levels (contact or air discharge).
When these components are mounted in a product to protect some of its fragile parts, the
behavior of this component, tested in the same conditions will be more predictable. The
wave shape of the clamping voltage given in worst case test conditions indicates the
magnitude of remaining voltage that the protected equipment can meet.
7
Revision history
Table 1.
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Document revision history
Date
Revision
24-Jun-2011
1
Changes
Initial release.
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