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Electromagnetic compatibility of ICs Seminar

Electromagnetic compatibility of ICs Seminar. Alexandre Boyer Senior lecturer. March 2008. Summary. Introduction EMC Basics concepts Emission/Susceptibility Origin Measurement methods EMC Models EMC Guidelines Conclusion / Future of EMC. Introduction. What is EMC ?. Two examples.

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Electromagnetic compatibility of ICs Seminar

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  1. Electromagnetic compatibility of ICs Seminar Alexandre Boyer Senior lecturer March 2008

  2. Summary • Introduction • EMC Basics concepts • Emission/Susceptibility Origin • Measurement methods • EMC Models • EMC Guidelines • Conclusion / Future of EMC

  3. Introduction

  4. 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.

  5. 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

  6. What is EMC ? CE mark 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 • For military applications : MIL-STD-461D, MIL-STD-462D • For aerospace applications : DO-160 • For integrated circuits : IEC 61963, IEC 62132

  7. Technology Scale Down Deep Deep Submicron Ultra deep Nano scale Micron Nano submicron submicron Lithography (µm) 80286 2.0 16MHz 80386 Industry z 1.0 33MH 486 66MHz Pentium 120MHz 0.3 Pentium III 0.7GHz 0.25µm 0.2 Pentium IV 3GHz 0.1 Research Pentium DualCore 2.2GHz 0.05 65nm 45nm 0.03 32nm Working 7nm 0.02 22nm device 0.01 83 86 89 92 95 98 01 04 07 10 13 Year Channel length • Channel length divided by 2 each 18 month in the 90’s • Research has 5 year advance on industry

  8. Technology Scale Down Embedded blocks transient current 16bit µC 0.5 A 32bit µC 2 A µC+DSP 10 A µC+DSP+.. Flash,eRam 30 A Multicore, DSP, FPGA, RF multiband 100 A System on chip 45nm 65nm Technology 0.18µm 0.12µm 90nm Complexity 50M 100M 250M 500M 1G Packaging 2001 1999 2003 2005 2007 Trend: Increase of complexity, IOs number, operating frequencies, transient current

  9. 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

  10. 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

  11. EMC of ICs Personnal entrainments Noise interferences System Equipments Printed circuit boards Safety systems Components Hardware fault Software failure Function Loss Two main concepts Susceptibility to EM waves Emission of EM waves

  12. EMC of ICs Interferences EMC at electronic system level Integrated circuits are the origin of parasitic emission and susceptibility to RF disturbances in electronic systems Emission Radiation Components Chip PCB System Noisy IC Sensitive IC Coupling System Chip Components PCB Susceptibility

  13. EMC Basics concepts

  14. 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

  15. EMC environment The “EMC” way of thinking

  16. 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

  17. Specific units Milli Volt Volt dBV dBµV 100 40 1 60 20 10 40 0.1 For example dBV, dBA : 1 0 20 0.01 -20 0.1 0 0.001 Extensive use of dBµV -40 0.01 -20 0.0001 0.001 -60 0.00001 -40 Emission and susceptibility level units Voltage Units Wide dynamic range of signals in EMC → use of dB (decibel)

  18. Specific units Power (Watt) Power (dBm) 90 1 MW 1 KW 60 1 W 30 1 mW 0 Exercise: Specific units 1 µW -30 1 mV = ___ dBµV 1 W = ___ dBm 1 nW -60 Emission and susceptibility level units Power Units The most common power unit is the “dBm” (dB milli-Watt)

  19. Specific units Emission and susceptibility level units dBµV dBµV/m 80 50 Class 4 70 40 Class 5 60 30 Class 5 50 20 40 10 3M 100M 30M 1G 300K 30K 1M 10M Conducted emission level (CISPR25) 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”

  20. Fourier transform Volt Time Fourier transform: principle dB Freq (Log) Fourier transform Frequency measurement Time domain measurement Invert Fourier transform Spectrum analyser Oscilloscope

  21. 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

  22. Fourier transform -20 dB/dec -40 dB/dec FFT Fourier transform - Example 50 % duty cycle trapezoidal signal Period T = 100 ns, Tr = Tf = 2 ns

  23. Emission spectrum Emission level has to be lower than customer specification EMC compatible Parasitic emission (dBµV) Specification for an IC emission 80 70 Aggressor IC 60 50 Measured emission 40 30 20 10 Radiated emission 0 -10 1 10 100 1000 Frequency (MHz)

  24. Susceptibility spectrum Immunity level has to be higher than customer specification Immunity level (dBmA) Specification for board immunity Current injection limit 50 40 30 Measured immunity 20 Victim IC 10 0 -10 A very low energy produces a fault -20 -30 -40 1 10 100 1000 Frequency (MHz)

  25. Notion of margin Parasitic emission (dBµV) Nominal Level Safety margin Process dispersion Measurement error/dispersion Component/PCB/System Ageing Environment Design Objective What is a margin ? • To ensure low parasitic emission ICs supplier has to adopt margins • Margin depends on the application domain

  26. 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 • Wire : Electric field coupling Example : The VSS supply track propagates noise

  27. Parasitic coupling mechanisms Coupling mechanisms - crosstalk • Parasitic coupling between nearby conductors. • Near field coupling Capacitive crosstalk Inductive crosstalk d d w w t t C12 L12 h C dielectric C h dielectric ground ground

  28. Impedance R,L,C vs. frequency Impedance profile of: • 50 ohms resistor Z÷10 at each decade • 100pF capacitor • 10nH inductor Z = constant • a real 100 pF SMD capacitor Z×10 at each decade

  29. Impedance Impedance Passive components – Real model Ceramic capacitor Inductor Carbon resistor

  30. Interconnection l 2a Skin effect Interconnect conductors Quasi static approximation : If l < λ/20, interconnections are considered as electrically small

  31. Interconnection • From the electromagnetic point of view: Coaxial line Microstrip line Link to conductor geometry and material properties • From the electric point of view : lossless conductor Equivalent electrical schematic Conductor impedance or Characteristic Impedance Z0:

  32. 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

  33. Interconnection Small conductor Large conductor Characteristic Impedance Z0: What is the optimum characteristic impedance for a coaxial cable ? Or ? Ideal values: • Maximum power : Z0 = 32  • Minimum loss: Z0 = 77  Cable examples: • EMC cable (compromise between power and loss) : Z0 = 50  • TV cable (minimize Loss): Z0 = 75 

  34. Impedance 50 ohm adapted systems Spectrum analyzer Waveform generator Tem cell Amplifier Gtem

  35. 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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