ESD protection design

California Micro Devices
http://www.calmicro.com
24-May-10
12
IEC 1000-4-2 Bench Test Specification
California Micro Devices
http://www.calmicro.com
24-May-10
California Micro Devices
http://www.calmicro.com
24-May-10
4Environment
Old - Manufacturing / Corporate New - Home / Outdoors / Person
California Micro Devices
http://www.calmicro.com
24-May-10
5
ESD Issues for the Designer
4 Bypass capacitor or series resistor/inductor 4 Spark gap
4 Discrete Zener diodes 4 Discrete PN diodes
4 Integrated PN diodes California Micro Devices
http://www.calmicro.com 24-May-10 14
4IEC 1000-4-2:1995 - for systems 4Machine Model (MM) - less common
EIA/JESD22-A115-A ANSI/EOS/ESD-S5.1-1993
4Charge Device Model (CDM) - less common
JESD22-c101 California Micro Devices
System Under Test
Terminal B
4 Used for system characterization 4 "Contact" v. "Air" discharge
Different levels Different applications
California Micro Devices
Integrated Diode Networks
4Superior downstream ESD protection
High speed response ESD current steered to GND or VCC
4Minimum Signal Degradation (Low C) Minimum 4Minimal board space, weight 4Low assembly/manufacturing costs 4Minimal Design-In Time 4Long-term reliability
California Micro Devices
http://www.calmicro.com
24-May-10
4
ESD problem is growing
4Circuits/Systems
Old - Robust ICs & Low speed signals New - Sensitive ICs & High speed signals
California Micro Devices
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24-May-10
2
What Is ESD?
4ESD = Electro Static Discharge 4Generation
Triboelectric (friction causes accumulation of charge) Induction (field induces charge)
California Micro Devices
http://www.calmicro.com
24-May-10
9
IEC 1000-4-2:1995 Standard
IEC 1000-4-2:1995 "Contact Discharge" Test Configuration
Terminal A
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24-May-10
3
ESD Damage of ICs
4Permanent
Oxide breakdown, shorts, opens, latch-up
4Temporary
Latch-up, ground bounce
4Latent
Degradation from an ESD event
ESD Protection Design Seminar
Jim Sutherland Senior Applications Engineer
California Micro Devices
http://www.calmicro.com
24-May-10
1
Outline
4 What is ESD? 4 What damage can it cause? 4 Why is the problem growing? 4 What are the issues for the designer? 4 How can we measure it? 4 How can we protect equipment from ESD?
4 Contact discharge is the preferred test method air discharges are not repeatable 4 Air discharges used where contact discharge cannot be applied 4 No implied equivalence in test severity between the two test methods
4 Pin-to-pin testing
N(N-1)/2 combinations
Terminal B
4 Used for component characterization 4 Widely used
California Micro Devices
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3 positive, 3 negative > 1 sec separation
Dual Polarity ESD Pulse Generator (100 pF capacitor discharging through 1.5 Kohm resistor)
Component Under Test
http://www.calmicro.com 24-May-10 7
Human Body Model (HBM)
Human Body Model (HBM) Test configuration
Terminal A
4 Discharge from 100pF capacitor through 1.5 kOhm resistor 4 6 ESD pulses
4 Discharge from 150 pF capacitor through 330 ohm resistor 4 6 ESD pulses
3 positive, 3 negative
Dual Polarity ESD Pulse Generator (150 pF capacitor discharging through 330 ohm resistor)
4 Must meet ESD specifications 4 Select ESD tolerant components 4 Minimize signal degradation (from R,L & C) 4 Board space / weight / proper design 4 Component cost 4 Assembly cost 4 Lifetime cost (stability) 4 Test the system
11wk.baidu.com
IEC 1000-4-2 Test Levels
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 15 x* Special x* Special - "x" is an open level. The level has to be specified in the dedicated equipment specification. If higher voltages than those shown are specified, special test equipment may be needed.
13
ESD Protection Techniques
4 Clamp diodes in IC
Not sufficient protection
4 Shielding
Low effectiveness Can degrade signal; many components; large board area Low cost; low stability; large board area High capacitance, many components; large board area Low capacitance; many components; large board area
24-May-10
8
HBM Current Waveform
Current Waveform Through a Short - HBM
8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0 100 200 300 400 500
Time (nS)
Rise Time: 2 nS < Tr <10 nS
4Discharge
Dielectric (air) breakdown
Electric field increases when charged bodies approach each other
Current flow into circuitry
California Micro Devices
California Micro Devices
http://www.calmicro.com
24-May-10
15
Choosing an ESD Diode Network
4 How many lines are needed? 4 How much capacitance? (e.g. < 5 pF) 4 What is the HBM rating? (e.g. ±15 kV) 4 What is the downstream clamp voltage? (e.g. 13 V @ 15 kV HBM pulse) 4 What is the contact discharge rating? (e.g. ±8 kV) 4 What is the air discharge rating? (e.g. ±15 kV) 4 What package? (e.g. 24-pin QSOP)
California Micro Devices
http://www.calmicro.com
24-May-10
6
International ESD Standards
4Human Body Model (HBM) - for devices
EIA/JESD22-A114-A ANSI/EOS/ESD-S5.1-1993 MIL-STD-883 (method 3015)
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24-May-10
10
IEC 1000-4-2 Current Waveform
60ns
Very fast rise time: Tr < 1nS
California Micro Devices
http://www.calmicro.com
24-May-10