EMC Refresh Presented by Sylvain LE BRAS Würth Elektronik eisos France

Transcription

1 EMC Refresh Presented by Sylvain LE BRAS Würth Elektronik eisos France

2 Agenda WHAT IS EMC? INDUCTIVE EMC SOLUTIONS BASICS INSERTION LOSS OF INDUCTIVE SOLUTIONS CAPACITIVE EMC SOLUTIONS BASICS INSERTION LOSS OF CAPACITIVE SOLUTIONS RADIATED EMC SHIELDING MATERIAL 2

3 EMC - Requirement CISPR* 22 Special International Committee on Radio Interference Non regulatory agency, but CISPR has adopted 150kHz to 30MHz Conducted 30MHz to 6GHz Radiated FCC** 15 Regulatory agency 450kHz to 30MHz 30MHz to 40GHz Conducted Radiated 5th harmonic of the highest frequency or 40GHz *Special International Committee on Radio Interference, Pub.22 **Federal Communications Commission, Part 15 3

4 What causes EMI in a product? Clock frequencies. E.g Crystal 25MHz, CPU 2.6GHz Data rates. DC/DC convertors and Switch mode power supplies (SMPS) E.g 135kHz, 2MHz E.g USB Mbps, SATA II 300Mbps All rights reserved by Würth Elektronik, also in the event of industrial property rights. All rights of disposal such as copying and redi 4

5 EMC Solutions = Inductive + Capacitive 5

6 Core material Filter application 6

7 Where can we find inductances? technical aspect a piece of wire wrapped on something We also see inductance in different shapes (shielded, round, square, ) or as parasitic effects 7

8 What is an EMC ferrite? technical aspect Sintered ferrite material applied to a wire As a function RF-Absorber frequency dependent filter in different forms 8

9 The magnetic field SOUTH N O R TH Induction in air: N O R TH Ring core ferrite SOUTH Rod core ferrite SOUTH N O R TH Air Induction in a ferrite: B 0 r H B 0 H linear function, because µr = 1 = constant! The relative permeability is a: -material -frequency -temperature -current -pressure -dependent parameter 9

10 Core material Filter application 10

11 Core material Storage application 11

12 Common mode or differential mode? Take a Snap Ferrite and fix it on the cable (both lines e.g. VCC and GND) if noise is reduced or noise immunity increase you have common mode interference e.g. Common mode choke If not you have differential mode interference e.g. chip bead ferrite 12

13 Common Mode Filter How it works It is a Bi-directional filter From device to outside environment From outside environment to inside device Intended Signal - Differential mode Interference Signal (noise) Common Mode Conclusion: almost no affect the signal - Differential mode high attenuation to the interference signal (noise) Common Mode 13 13

14 Common mode choke construction bifilar sectional 14

15 Common mode choke construction WE-Star TEC: Is it a Common Mode Choke? Yes, Common Mode Choke with 1 turn Comparable with bifilar winding style Both absorb common mode interferences 15

16 WE-SL1 - sectional wound Common Mode Chokes for Data & Signal Lines WE-SL2 - bifilar & sectional wound (denoted with a S) WE-SL3 - Either 2 or 3 wire. bifilar or Trifilar wound WE-SL5 - bifilar & sectional wound (denoted with a S) WE-SL5HC - Maximum current 5A - sectional wound WE-SL Either 2 or 4 wire. bifilar or quadfiliar wound WE-SCC bifilar wound 16

17 WE-CMB NiZn Common Mode Chokes for Power Lines WE-CMBH - Horizontal WE-LF WE-LF SMD WE-TFC WE-TFCH - Horizontal WE-FC 17

18 INSERTION LOSS OF INDUCTIVE SOLUTIONS 18

19 The problem(s) 19

20 Insertion Loss Definition System attenuation Impedance Z A ZF ZB A 20 log Z A ZB in (db) 20A in ( ) 10 Z Z Z Z A B A B ZF 20

21 System impedances 1 10 >90 21

22 Quick solution 1. 1.Require 20dB of attenuation at 125 MHz Attenuation (db) 2. Know that it is a power cable 3. Power port has 10 Ω impedance 12 Impedance of ferrite (Ω) Result is a minimum impedance of 180Ω 220 WE Academy Public Mai 10 AR EMC November

23 Finding inductive solution 23

24 REDExpert : List 24

25 25

26 The result 26

27 CAPACITIVE EMC SOLUTIONS BASICS 27

28 Ideal & real capacitor Definition Impedance of perfect capacitor 2 f SRF C = capacitance 1 Z jc in ( ) Impedance of real* capacitor Ca pa cit ive a rea a e r ea v i t uc d n I 1 Z ESR jlesl jc 28

29 Typical action in EMC EN : 06 (A1A2) alim - Classe: - Moyenne/ EN : 06 (A1A2) alim - Classe: - QCrête/ Mes.Peak (Phase1) 130 dbµv Differential mode Common mode 0 9kHz Fréquence (MHz) 30MHz Ligne: Phase1 29

30 INSERTION LOSS OF CAPACITIVE SOLUTIONS 30

31 Conducted EMC Capacitive solution 62kHz +6dB 31

32 Attenuation provided by a capacitor Example = 50Ω = 105Ω 1 A 20 log 1 (100 / 105) (100 jc ) 1 Z jc 2 f Capacitance 0 10nF 100nF 1µF 10µF 62Khz -5,81dB -7,4dB -15,3dB -32dB -52dB in ( ) 32

33 Conducted EMC Capacitive solution 62kHz now 6dB margin 33

34 RADIATED EMC 34

35 The problem Example, Radiated Emission plot 35

36 Insertion Loss Definition System attenuation Impedance Z A ZF ZB A 20 log Z A ZB in (db) 20A in ( ) 10 Z Z Z Z A B A B ZF 36

37 System impedances 1 10 >90 37

38 Quick solution 1. 1.Require 20dB of attenuation at 125 MHz 2. Know that it is a power cable Attenuation (db) 3. Power port has 10 Ω impedance Result is a minimum impedance of 180Ω 180 Impedance of ferrite (Ω) WE Academy Public Mai 10 AR EMC November

39 The result Example Radiated Emission plot Example with Ferrite fitted 39

40 SHIELDING MATERIAL 40

41 EMI Shielding material Key points Applications Shielding of non metallic enclosures Bonding of metallic enclosures Absorbing (Attenuating) EMC Phenomena Radiated Emissions Radiated Immunity Effective frequency range 30MHz to 18GHz 41

42 EMI Shielding material WE-LS WE-FAS EMI 42

43 Can WE help you? Over the limit? Conducted Common mode Cables / Long tracks 10 ~ 100MHz Radiated Tracks around µc 100MHz ~ 1GHz Differential mode FPGA / RF / DSP 1GHz ~ 20GHz 43