ESD_Compliance.pdf

APPLICATION NOTE
ESD Compliance Testing and Recommended
Protection Circuits for GaAs Devices
Introduction
Skyworks conducts ESD testing at both the device and system
levels. These tests are based on the requirements outlined in:
ESD Association 2.0 Handbook
– Human Body Model (HBM)
– Charged Device Model (CDM)
● IEC 61000-4-2 International Standard: Testing and
Measurement Techniques
– Electrostatic Discharge Immunity Test
● MIL-STD-1686
● MIL-HDBK-263
● Skyworks designed and tested several circuits that provide
adequate ESD protection for Skyworks GaAs switches
●
Human Body Model (HBM)
This testing model simulates the ESD discharge delivered from the
fingertip of an individual to a device. The model uses an RC circuit,
such as the one shown in Figure 1, to deliver an exponentially
decaying current pulse. Component ESD sensitivity levels for HBM are
defined in Table 1.
The testing conducted consists of applying one positive and one
negative pulse to the component, allowing a 0.3 second interval
between pulses. A set of devices is exposed to these pulses at a
given voltage level and pin grounding combinations, the device is
tested for full static and dynamic parameters.
A typical test run consists of 20 devices. A set of five (5) devices
is exposed to each level in 50 V increments. Most device level
testing ranges from 150 V – 500 V.
Device Level ESD Testing
1.5 kΩ
Device level ESD classification is conducted as part of Skyworks
standard qualification process, with the intent to fully characterize a component’s electrostatic discharge susceptibility.
The Failure Analysis Laboratory at Skyworks utilizes an Oryx
Instrument’s Bench Top ESD tester. This instrument allows Human
Body Model (HBM) and Machine Model (MM) ESD events to be
applied to devices. In addition, Skyworks performs ESD testing to
Charged Device Model (CDM). These tests are conducted on the
packaged device.
Class
Voltage Range
Class 0
0– ≤ 249 V
Class 1A
250– ≤ 449 V
Class 1B
500– ≤ 999 V
Class 1C
1000– ≤ 1999 V
Class 2
2000– ≤ 3999 V
Class 3A
4000– ≤ 7999 V
Class 3B
> 8000 V
High Voltage
Supply
100 pF
Device Under
Test
Figure 1. HBM Circuit for Delivering a Current
Pulse to a Device.
Table 1. ESD Component Sensitivity Classifications
for HBM ESD Testing.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 15, 2004
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APPLICATION NOTE • ESD COMPLIANCE TESTING AND RECOMMENDED PROTECTION CIRCUITS FOR GAAS DEVICES
Charged Device Model (CDM)
System Level ESD Tests
This testing model simulates the ESD discharge event that occurs
as a charged component discharges to another object at a different electrostatic potential. Component ESD sensitivity levels for
CDM are defined in Table 2.
To better understand device performance within an application,
Skyworks conducts ESD testing at the system level utilizing the
guidelines specified in IEC 61000-4-2. The IEC standard defines
typical discharge current waveforms, range of test levels, test
equipment, test configuration, and test procedure. System-level
testing simulates the device in an application, such as a switch in
a cellular handset. Test environment must emulate actual enduse environment.
Class
Voltage Range
Class C1
< 125 V
Class C2
125– < 250 V
Class C3
250– < 500 V
Class C4
500– < 1000 V
Class C5
1000– < 1500 V
Class C6
1500– < 2000 V
Class C7
> 2000 V
Table 2. ESD Component Sensitivity Classifications
for CDM ESD Testing.
Three samples are submitted to CDM test for each voltage level.
The device’s potential is raised by applying a test voltage to the
field charge electrode, see Figure 2 (Field Induced CDM Simulator).
Five positive and negative discharges are applied to each pin,
allowing enough time between discharges for the device to reach
the full test voltage. Test voltages applied start at the 100 V level
and are increased by 50 V increments. The device passes a voltage
level when all three (3) samples stressed at this level pass. The
device is tested for full static and dynamic parameters.
A typical test run consists of 20 devices. A set of five (5) devices is
exposed to each level in 50 V increments.
50 Ω Semi-rigid
Coaxial Cable
Top Ground
Plane
Support
Arm
FR-4
Radial 1 Ω
Resistor
Pogo Probe
Device
Under Test
Field-charging
Electrode
Insulating
Fixture
300 mΩ
Charging
Resistor
High Voltage
Power Supply
Figure 2. Field Induced CDM Simulator.
Test Configuration
The test configuration used at Skyworks (Figure 3) corresponds
to that outlined in the IEC Standard for tabletop equipment. The
configuration consists of a 6 mm thick, 122 cm x 122 cm square
aluminum plate on the laboratory floor. This plate is connected to
earth ground. The discharge return cable of the ESD generator is
connected to this ground reference plane.
ESD Pulse
Generator
Oscilloscope
Device Test
Fixture
470 kΩ
Horizontal Coupling Plane
High Voltage Probe
Ground Reference Plane
Figure 3. Sketch of the ESD Immunity Test Configuration.
A wooden table 0.8 m high sits on top of the ground reference
plate. A horizontal coupling plane of the same dimensions as the
ground reference plane is bolted on the wooden table. The device
is centrally located on this top surface. The fixture that holds the
device is insulated from the horizontal coupling plane by a
0.5 mm thick, 30 cm x 46 cm insulating sheet.
An SMA cable is fed through a hole in the horizontal coupling
plane in order to connect to the DUT fixture. This cable is connected to the high voltage probe that, in turn, connects to the
oscilloscope. This allows the voltage at the outputs of the device
to be recorded.
ESD Protection Circuit
GaAs devices are used in different system architectures and are
applied as power amplifiers, switches, attenuators, detector/couplers, etc. In general, devices that are well embedded within the
circuit are better protected, however, some applications may
require an ESD protection circuit. A possible ESD protection mode
utilizes a band pass filter, as shown in Figure 4.
The figure is of a Band Pass Filter (BPF) Protection Circuit for
SP4T Switch IC. The BPF shown was mounted in front of a SP4T
Switch IC in series.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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September 15, 2004 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice.
APPLICATION NOTE • ESD COMPLIANCE TESTING AND RECOMMENDED PROTECTION CIRCUITS FOR GAAS DEVICES
Skyworks recommends the use of spark gap, band pass filters,
and Chebyshev filters as ESD protection circuitry.
ESD Pulse
Applied
Here
4.7 nH
4.7 nH
Device
Under
Test
2 pF
ESD Protection Circuit Recommendations for
Portable, Handheld Devices
4.7 nH
2 pF
2 pF
again after the test. The unbiased device is first exposed to ESD
air discharge of 16 kV. Upon passing this level of test, a device is
biased in a functional state (for example, RX mode for a switch)
and exposed to incrementally larger contact mode ESD pulses of
each polarity.
Portable electronic devices, like cellular handsets, contain
numerous RF and DC components, such as amplifiers, attenuators, switches and filters. Some of them may require ESD
protection, some may not. However, to protect even one ESD sensitive chip, like GaAs switch, it is necessary to consider the whole
handset as an ESD- sensitive system. Since the ESD pulse can
leak into the switch through either one of the RF inputs, outputs,
or even through the DC bias paths. Here are points to consider:
Figure 4. Band Pass Filter—ESD Protection Circuit.
0
-5
-10
Proper shielding of the whole handset is crucial.
Bias source should not be located in the poorly shielded section
of the board. Bias paths should not be running close to the poorly
shielded sections Example: volume buttons on the side of the
case can be a physical opening in the casing of the handset
through which the ESD pulse can jump onto the bias path.
● Layout of the circuit board is very important, especially the
location of the ESD sensitive part. There should be no other
closely located components that can serve as a path for the
ESD pulse into the sensitive part.
● The ESD protective circuit placed in front of the ESD sensitive
part should not significantly degrade the RF performance.
●
-15
●
-20
S11
S21
-25
-30
0
6.0
Frequency (1 GHz/Div.)
Band Pass Filter Performance
Test Procedure
Skyworks conducts tests on devices mounted on RF test fixture
boards to the electrostatic discharge as outlined in the IEC
Standard. The fixture is a printed circuit board with SMA connectors to the stripline leading to the device. The device is held in
place on the fixture by a spring-loaded plunger (Figure 5).
Considering the recommendation by IEC (International
Electrotechnical Commission) and various individual application
requirements, both contact and air discharge modes are applied
to all system-level tests. The test levels used by Skyworks are
outlined in Table 3.
Skyworks has tested several circuits that provide adequate ESD
protection with various degrees of shielding. Protection circuits
insertion loss varied from 0.06–0.15 dB at 0.88 GHz and from
0.05–0.1 dB at 1.9 GHz, depending on the circuit topology.
Since portable handset designs differ from manufacturer to manufacturer, the ESD protection issue has to be approached on a
specific manufacturer’s design basis.
The device is exposed to only one level of ESD energy during the
test. The device is RF tested prior to the ESD test, then tested
Contact Discharge
Air Discharge
Level
Test
Voltage (kV)
Level
Test
Voltage (kV)
1
2
1
2
2
4
2
4
3
6
3
8
4
8
4
16
Table 3. IEC Standard Defined Test Levels for
Contact and Air Discharge Modes.
Figure 5. Photograph of the ESD Pulse Application to the
Test Fixture.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • September 15, 2004
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APPLICATION NOTE • ESD COMPLIANCE TESTING AND RECOMMENDED PROTECTION CIRCUITS FOR GAAS DEVICES
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September 15, 2004 • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice.
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