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Electromagnetic compatibility
of ICs Seminar
Alexandre Boyer
Senior lecturer
March 2008
1
March 2008
Summary

Introduction

EMC Basics concepts

Emission/Susceptibility Origin

Measurement methods

EMC Models

EMC Guidelines

Conclusion / Future of EMC
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March 2008
Introduction
What is EMC ?
Two examples
« Disturbances of flight instruments
causing trajectory deviations appear
when one or several passengers switch
on electronic devices. » (Air et Cosmos,
April 1993)
29th July 1967 : accident of the American
aircraft carrier Forrestal. The accidental
launching of a rocket blew gas tank and
weapon stocks, killing 135 persons and
causing damages which needed 7 month
reparations. Investigations showed that a
radar induced on plane wiring a sufficient
parasitic voltage to trigger the launching of
the rocket.
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March 2008
What is EMC ?
Definition of EMC
« The ability of a device, equipment or system to function
satisfactorily in its electromagnetic environment without
introducing intolerable electromagnetic disturbance to
anything in that environment. »
 Guarantee the simultaneous operation of all nearby electric or electronic
devices and the safety of users in a given electromagnetic environment
 Reduce parasitic electromagnetic emission and their sensitivity or
susceptibility to electromagnetic interferences
 Maximum levels and methods to characterize emission and susceptibility
of an equipment are defined by standards
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March 2008
What is EMC ?
Examples of EMC standards


The existence of EMC specifications is linked to the safety and
robustness level that an equipment must reach.
EMC standards for automotive, aerospace, military, transport, medical,
telecommunication applications, but also for commercial products
• European EMC directive 89/336/EEC about electronic
products EMC requirements
• IEC-TC77 and CISPR : IEC technical committee related to
EMC standards
• For automotive applications : ISO 7637, ISO 11452, CISPR
25, SAE J1113
CE mark
• For military applications : MIL-STD-461D, MIL-STD-462D
• For aerospace applications : DO-160
• For integrated circuits : IEC 61963, IEC 62132
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March 2008
Technology Scale Down
Micron
Deep
submicron
Submicron
Lithography (µm)
80286
2.0
Channel
length
Ultra deep Nano scale Deep
Nano
submicron
16MHz
1.0
80386
33MH z 486
Industry
66MHz
Pentium
120MHz
0.3
Pentium III
0.7GHz
0.25µm
0.2
Pentium IV
3GHz
0.1
Research
Pentium DualCore
2.2GHz
65nm
45nm
32nm
0.05
0.03
• Channel length divided by 2
each 18 month in the 90’s
• Research has 5 year advance
on industry
Working 7nm
device
0.02
22nm
0.01
83
86
89
92
95
98
01
04
Year
7
March 2008
07
10
13
Technology Scale Down
System on chip
Technology
0.18µm
0.12µm
50M
100M
90nm
45nm
65nm
Complexity
250M
500M
1G
Packaging
Embedded blocks
transient current
1999
2001
16bit µC
0.5 A
32bit µC
2A
2003
µC+DSP
10 A
2005
µC+DSP+..
Flash,eRam
30 A
2007
Multicore,
DSP, FPGA,
RF multiband
100 A
Trend: Increase of complexity, IOs number, operating frequencies, transient current
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March 2008
EMC of ICs
Why EMC of IC ?
• Since mid 80’s, printed circuit board designers have put continuous
efforts in reducing parasitic emission and interference coupling
within their systems
• Until mid 90’s, IC designers had no consideration about EMC
problems in their design..
• Many EMC problems originate from ICs (3rd origin of IC redesign !)
• With the increased clock speed and chip size, IC generate increased
amount of noise
•  EMC must be handled at IC level
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March 2008
EMC of ICs
EMC of IC topics
 Improve or develop EMC measurement methods to respond to new
customer’s requests
 Develop simulation tools to predict EMC of IC behavior
 Develop design guidelines aiming at reducing emission and susceptibility
levels
Emission
level
measurement
Simulation
Customer’s specifications
IC emission
spectrum
Target
frequency
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March 2008
EMC of ICs
Two main concepts
Susceptibility to EM waves
Emission of EM waves
Personnal entrainments
Noise
interferences
System
Equipments
Printed circuit boards
Components
Safety systems
Hardware fault
Software failure
Function Loss
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March 2008
EMC of ICs
EMC at electronic system level
Integrated circuits are the origin of parasitic emission and susceptibility to
RF disturbances in electronic systems
Emission
Chip
Components
PCB
System
Radiation
Noisy
IC
Interferences
Sensitive
IC
Chip
Coupling
Components
PCB
System
Susceptibility
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March 2008
EMC Basics
concepts
Summary
1. Basic Principles
2. Specific Units
3. Fourier Transform
4. Emission Spectrum
5. Susceptibility Threshold
6. Notion of margin
7. Parasitic coupling mechanisms
8. Impedance
9. Interconnections
10. Conclusion
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March 2008
EMC environment
The “EMC” way of thinking
Electrical domain
Electromagnetic domain
Voltage V (Volt)
Electric Field E (V/m)
Current I (Amp)
Magnetic field H (A/m)
Impedance Z (Ohm)
Characteristic impedance Z0 (Ohm)
Z=V/I
Z=E/H
P=I2 x R (watts)
P=H2 x 377 (watts/m2)
far field conditions
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March 2008
Specific units
How do we present EMC results?
Why in frequency domain (Hz) ?
• Time domain aspect is dominated by the major frequency harmonics
• Distinguish contributions of each harmonics, even small ones
Why in logarithm scale (dB) ?
• Signals are composed of high and low amplitude harmonics
• Very large dynamic (from µV to several mV)
• Logarithm scale is requested
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March 2008
Specific units
Emission and susceptibility level units
Milli
Volt
Voltage Units
Volt
dBV
Wide dynamic range of signals in EMC
→ use of dB (decibel)
100
40
1
60
10
20
0.1
40
1
0
0.01
20
0.1
-20
0.001
0
0.01
-40
0.0001
-20
0.001
-60
0.00001
-40
For example dBV, dBA :
dBV  20 logV 
dBA  20 log A
Extensive use of dBµV
 V 
  20 logV   120
VdBµV  20 log
 1µV 
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March 2008
dBµV
Specific units
Emission and susceptibility level units
Power Units
The most common power unit is the “dBm” (dB milli-Watt)
PdBmW
 P 
 10 log W   10 logPW   30
 1m W 
Power
(Watt)
Power
(dBm)
1 MW
90
1 KW
60
1W
30
1 mW
0
1 µW
-30
1 nW
-60
Exercise: Specific units
1 mV = ___ dBµV
1 W = ___ dBm
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March 2008
Specific units
Emission and susceptibility level units
dBµV
dBµV/m
80
50
Class 4
70
60
40
30
Class 5
50
20
40
30K
10
1M
300K
Class 5
3M
30M
Conducted emission level
(CISPR25)
10M
100M
Radiated emission level
(CISPR25)
CISPR 25 : “Radio disturbance characteristics for the protection of receivers used on board
vehicles, boats, and on devices – Limits and methods of measurement”
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March 2008
1G
Fourier transform
Fourier transform: principle
Volt
dB
Time
Time domain measurement
Freq (Log)
Fourier transform
Frequency measurement
Invert Fourier transform
Spectrum analyser
Oscilloscope
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March 2008
Fourier transform
Fourier transform
Why Frequency domain is so important ?
Time domain
Frequency domain
Only high level harmonics contribution
appears
Contribution of each harmonic appears
Low level harmonics
contribution
User’s specification
FFT
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March 2008
Fourier transform
Fourier transform - Example
1
0.35
ou
Tr
Tr
-20 dB/dec
1
T
-40 dB/dec
FFT
1
Tr
50 % duty cycle trapezoidal signal
Period T = 100 ns, Tr = Tf = 2 ns
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March 2008
Emission spectrum
Emission level has to be lower than customer specification
Parasitic emission
(dBµV)
EMC compatible
80
Specification for
an IC emission
70
60
Aggressor IC
50
Measured
emission
40
30
20
10
Radiated emission
0
-10
1
10
100
Frequency (MHz)
23
1000
March 2008
Susceptibility spectrum
Immunity level has to be higher than customer specification
Immunity level
(dBmA)
50
Specification for
board immunity
Current injection limit
40
30
Measured
immunity
20
10
Victim IC
0
-10
A very low energy
produces a fault
-20
-30
-40
1
10
100
Frequency (MHz)
24
1000
March 2008
Notion of margin
What is a margin ?
Parasitic emission (dBµV)
Nominal Level
Safety margin
 To ensure low parasitic emission ICs
supplier has to adopt margins
Process dispersion
Measurement error/dispersion
Component/PCB/System Ageing
Environment
Design Objective
 Margin depends on
the application domain
Domain
Lifetime
Margin
Aeronautics
30 years
40 dB
Automotive
10 years
20 dB
Consumer
1 year
0 dB
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March 2008
Parasitic coupling mechanisms
Coupling mechanisms
Radiated mode –
Antenna coupling
Conducted mode – Common
impedance coupling
The EM wave propagates
through the air
• Loop : Magnetic field coupling
Example : The VSS
supply track propagates
noise
• Wire : Electric field coupling
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March 2008
Parasitic coupling mechanisms
Coupling mechanisms - crosstalk
• Parasitic coupling between nearby conductors.
• Near field coupling
Capacitive crosstalk
d
t
h
Inductive crosstalk
d
w
t
C12
dielectric
ground
C
0.1
0.17
d
 w
 

 w
t

C   o r 1.1  0.79   0.46   1  0.87e h  
 h

h
h



t
d  d

C12  o r   1.2    1.15
d
h h


0.1
2.22
L12
h
C
w  d


 0.253ln1  7.17   0.54
d  h


0.64
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dielectric
ground
L




w
o  8h

ln
 1
2  w  t 
o  d  2r 2  r  2h 2 
tw
L12 
ln
,
r


2  d  2r 2  r 2
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
March 2008
Impedance
R,L,C vs. frequency
Impedance profile of:
•50 ohms resistor
•100pF capacitor
•10nH inductor
Z = constant
•a real 100 pF SMD
capacitor
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March 2008
Impedance
Passive components – Real model
Ceramic capacitor
Inductor
Carbon resistor
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March 2008
Interconnection
Interconnect conductors
l

2a
1
f
Skin effect
R  Rdc  Rac
l
Rdc 
 a 2
L
Rac 
ol   2l  
  ln   1
2   a  
l
 2a
Quasi static approximation : If l <
λ/20,
interconnections
are
considered as electrically small
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March 2008
Interconnection
Conductor impedance or Characteristic Impedance Z0:
• From the electromagnetic point of view:
Coaxial line
E
Z0 
H
Microstrip line
Link to conductor geometry and material properties
• From the electric point of view :
R  jL
Z0 
G  jC
lossless
conductor
L
Z0 
C
Equivalent electrical schematic
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March 2008
Interconnection
Impedance matching
Why impedance matching is fundamental ?
Not adapted: the line suffers
ringing, insertion losses
Adapted: the line is transparent
Voltage
Voltage
time
time
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March 2008
Interconnection
Characteristic Impedance Z0:
Small conductor
What is the optimum characteristic
impedance for a coaxial cable ?
Small
conductor
Power handling
X
weight
X
Low loss
x
Small capacitance
x
Small inductance
Low Impedance
Or ?
Large
conductor
Ideal values:
• Maximum power : Z0 = 32 
X
Bending
Large conductor
• Minimum loss: Z0 = 77 
Cable examples:
x
• EMC cable (compromise between
power and loss) : Z0 = 50 
x
• TV cable (minimize Loss): Z0 = 75 
x
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March 2008
Impedance
50 ohm adapted systems
Spectrum analyzer
Waveform generator
Tem cell
Amplifier
Gtem
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March 2008
Conclusion
• Key words of EMC for integrated circuits have been presented
• The origin of parasitic emission in Ics has been illustrated
• The trend to decrease supply voltages increase the IC
susceptibility
• Specific units used in EMC have been detailed
• The Fourier Transform is a very important tool for the
characterization of EM signals
• The notion of impedance has been introduced
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March 2008