Origin of Emission and Susceptibility in ICs

Printed circuit boards EMC Introduction Two main concepts: Susceptibility to EM waves Emission of EM waves Components Printed circuit boards Equipments System Noise Personnal entrainments Safety systems interferences Susceptibility to radio frequency interference is illustrate in the case of a very high radar wave illuminating an airplane. This situation is very common at the proximity of airports. A Giga-watt pulse is received by the the plane, which captures some energy which may flow to the equipment, the board and finally to the component. On the other hand, the parasitic emission due to the integrated circuit inside a car may jeopardize the correct behavior of personal devices such as mobile phones, and RF links. In some case, the parasitic energy may be high enough to parasite the safety systems of the car. Hardware fault Software failure Function Loss

Source of Electromagnetic Interferences Natural disturbances (cosmic rays, thunder) Radio communications, wireless, radars,… IC Electrical Overstress IC Inductive loads, motors

Origin of Parasitic Emission Basic mechanisms for core current: CMOS inverter exemple VDD Switching current IDD (0.1mA) IDD (0.1mA) ISS (0.1mA) Vin Voltage Time Output capa VOUT VSS ISS (0.1mA) Time One of the major source of perturbation is the current flowing inside each elementary gate of the integrated circuit. Let us consider the CMOS inverter, supplied by a high voltage VDD (2V in 0.18µm) and ground VSS (0V). When the input falls to 0 (i.e logic level “0”), a current (around 0.5mA) charges the capacitance through the pull up device. When the input rises to 2V, that is a logic level “1”, a similar current flows through the pull down device and discharges the capacitance.

Origin of Parasitic Emission The increasing speed and the high level of integration generate a stronger noise: 50ps i(t) Time Vdd Vdd i(t) Vss Vss Internal switching noise Switching gates Simultaneous Switching Noise Main noise sources comes from AC current sources: Clock-driven blocks, synchronized logic Memory read/write/refresh I/O switching

Increase parasitic noise Origin of Parasitic Emission Why technology scale down makes things worse ? Time New process Volt Old process Current level keeps almost constant but: Faster current switching Stronger di/dt Increase parasitic noise Current di/dt Old process Reduc Voltage swing => less E field With the technology scale down, the supply voltage is reduced and the signals switch faster within interconnects (From voltage to scaled voltage). In 0.18µm technology, the switching is about 100ps (Pico-second or 10-12 second), with a 2V swing. Concerning currents, the amplitude of elementary peaks appearing on supply lines of each elementary gates are sharper, but their amplitude remains constant (0.5mA in 100ps, per gate). Consequently, stronger di/dt are observed, leading to increased emission problems. New process Time

Origin of Parasitic Emission Example: evaluation of switching current in an IC 0.1 mA / Gate in 100ps 1 Billion gates (32 Bit Micro) => 100A 10% switching activity => 10A 10% spreading of current peak (non synchronous switching) => 1A in 1ns 0.1 mA Ampere 0.1 ns time Vdd Vss i(t) Current / gate Ampere 1 ns time Current / Ic 1 A 0.1 ma/gate in 100 ps, 10 million (base band), 10 K(8bits), 100K (16 bits), 1M (32 bits). % switching activity = 10 %, /10 because spread current = 1 A peak sur 1 ns. 16 bits : 100 mA sur 1 ns, 32 bits = 1A 500 ps…

Origin of Parasitic Emission Example: evaluation of SSN L=0.6nH/mm L=1nH/mm VDD Lead = 10 mm Evaluate SSN amplitude 1 A en 1 ns Puce Lead = 10 mm VSS

Susceptibility issues Power supply decrease & Noise margin reduction : => Increase of ICs sensibility to parasitic noise Supply (V) 5.0 3.3 2.5 I/O 1.8 1.2 Tension cœur: réduire la puissance consommée, fragilité des oxyde Tension I/O: reduction => aller + vite de 0 à VDD, mais – rapide pour des raison de compatibilité entre techno 0.8 Core 0.5µm 0.35µm 0.18µm 90nm 65nm 45nm Technology

Susceptibility Issues 1-10GHz : Packages act as very good antennas Antenna optimal size: EMC of ICs issues La longueur d’onde est de 10cm a 3GHz et l’antenne optimale a une taille de 25mm (lamda/4) Le boitier est une bonne antenne en émission et réception dans ces bandes de fréquence

Susceptibility Issues Multiple parasitic electromagnetic sources Components issues Power HF VHF UHF SHF xHF THF 1GW Radar Météo Radars Satellites 1MW TV UHF MWave 1KW TV VHF Stat. de base Badge Hobby 1W GSM UMTS Multitude de sources de puissance différente entre 30MHz et 30GHz => la bande de fréquence dangereuse est très large et les modes d’agression sont très varies (continu, impulsionnel), la distance à l’émetteur varie aussi du km au cm => problème complexe et de moins en moins déterministe (multiplicité de cas) Radar Hobby DECT 1mW Frequency 3 MHz 30 MHz 300 MHz 3 GHz 30 GHz 300 GHz

Immunity suddenly decreases? Immunity increases with Freq Susceptibility Issues Susceptibility trends vs frequency Immunity suddenly decreases? Immunity increases with Freq Barber, Herke, IEE Electromagnetic Hazard, 1994

Susceptibility Issues Desynchronization issues Jitter is becoming increasingly important in design of logic circuit due to rising operating frequencies. The increase of operating frequencies of digital circuits reduces their dynamic margin EMI on supply EMI induced jitter Bit error Dynamic failure EMI induced jitter

Emission / Susceptibility Issues Block type Emission Susceptibility Fast digital I/O ++ - Power switch output -- Oscillator / PLL / Clock circuitry Charge pump Digital block supply + Analog input DC/DC converter

EMC environment EMC for Integrated Circuits requires various expertise High frequency measurement High frequency modelling 2D, 3D modelling Electrical modelling IC design IC floorplan Caleidoscope du materiel etrange de la CEM

EMC Measurement methods

EMC measurement methods Why EMC standard measurement methods Check EMC compliance of ICs, equipments and systems Comparison of EMC performances between different products, different technologies, designs, PCB routings Improve interaction between customers and providers (same protocols, same set-up)

Radiated or conducted coupling Emission measurement methods Emission – General measurement set-up Control - Acquisition Coupling device Coupling network Antennas Wave guide Device under test Radiated or conducted coupling Acquisition system Spectrum analyzer EMI receiver Oscilloscope 50Ω adapted path Emission requirements verified ?

Emission measurement methods International standards for IC emission measurement methods IEC 61967-2 (TEM : 1GHz) IEC 61967-3/6 (Near field scan, 5GHz) IEC 61967-4 (1/150 ohm, 1 GHz) IEC 61967-5 (WBFC, 1 GHz) IEC 61967-7 (Mode Stirred Chamber: 18 GHz) (GTEM 18 GHz) Gros travail de normalisation => cadrer et normaliser les méthodes de mesures, permet les comparaisons, permet la discussion entre client et fournisseur

Emission measurement methods Example of emission measurement set-up – TEM cell measurement Chip under test Spectrum Analyzer Shielding Septum Far end (to absorb ers 50 W termination) aperture 1 aperture 2 Near end (to receiver) Pre-amplifier GTEM cell Emission spectrum

Immunity measurement methods Immunity – General measurement set-up Injected level Extraction Failure detection Disturbance generation Harmonic signal Transients Burst Coupling device Coupling network Antennas Wave guide 50Ω adapted path Radiated or conducted coupling Device under test Immunity requirements verified ?

Immunity measurement methods International standards for IC susceptibility measurement methods IEC 62132-2 (Bulk Current Injection : 1 GHz) IEC 62132-3 (Direct Power Inj 1GHz) IEC 62132-4 (TEM/GTEM) IEC 62132-5 (WBFC 1 GHz) New proposal: (LIHA : 10 GHz) Still research: (NFS 10 GHz)

Susceptibility threshold Immunity measurement methods Example of immunity measurement set-up Signal Synthesizer Decoupling network Chip under test Failure detection Pforw Prefl Directional coupler DPI Capacitor Amplifier Oscilloscope Acquisition card Susceptibility threshold

Impedance extraction Equipment to extract impedance profile of board, package, chip Frequency domain Time domain Vector Network Analyzer Time Domain Reflectometry

EMC equipments Expensive …. Complete EMC laboratory : 500 K€ Main equipments for EMC – typical prices Vector Network Analyzer 10 GHz (100 K€) Amplifier 3 GHz 100W (60 K€) Spectrum analyzer 40 GHz (40 K€) GTEM cell 18 GHz (15 K€) Signal Synthesizer 6 GHz (20 K€) Expensive …. Complete EMC laboratory : 500 K€