EMC-conform development of a Tablet-PC

Transcription

1 EMC-conform development of a Tablet-PC January 21, 2014 Johannes Biner Electrosuisse Montena EMC Bernstrasste 93 CH Bern Tel [email protected]

2 Programm Electrosuisse Montena EMC From the Directive to the Standards and the Concepts Process of an EMC-conform development of a printed circuit board 2

3 Electrosuisse Montena EMC 2 Labs in Rossens and Bern 9 Engineers for EMC-measurement and consulting for EMC conform schematics, construction and courses. 3

4 Addresses of Montena EMC Main URL: Rossens: route de Montena 75 CH-1728 Rossens Tel: Bern: Ostermundigenstrasse 93; 3006 Bern

5 EMC-labs of Electrosuisse 4 Labs: Fehraltorf, Zürich-Albisrieden, Zürich-Neuenhof and St. Gallen 30 Engineers for EMC und Safety 5

6 Addresses of electrosuisse Fehraltorf: Luppmenstrasse 1; CH-8320 Fehraltorf Leiter Verkauf Industrie und Handel: Leiter EMV-Labor: Zürich: Albisrieden Electrosuisse Albislab Albisriedenstrasse 199; CH-8047 Zürich Zürich: Neuenhof Ringstrasse 10; CH-5432 Neuenhof St. Gallen Blumeneggstrasse 50; CH-9403 Goldach Tel:

7 Programm Electrosuisse Montena EMC From the Directive to the Standards and the Concepts Process of an EMC-conform development of a printed circuit board 7

8 Why you should contact us... Idea Money Yes Conform? Diverse concepts: - Elec. Circuit / System - Construction - EMC & Safety Bad luck High costs No Testing Production Description Construction Layout of the PCB Montena EMC / Electrosuisse: EMC & Safety 8

9 Dr. Braun please develop... Radio Port LAN Port USB- SST PC Card Slot Power Port 9

10 Relevant directives Low power directive (73/23/EWG) Applicable since Relevant since EMC directive (89/336/EWG)!! Actual: 2004/108/EG!! Applicable since ( ) Relevant since ( ) R&TTE directive (99/5/EWG) Applicable since Relevant since

11 Different types of standards Generic standard Product family standard Product standard } Levels and Limits Product and Product Family Standards take priority over Generic Standards Basic standards - Emission Description - Immunity of the Test } 11

12 Where you will find the standards? You can find a list of harmonised standards at: For our example (Pad): EN (EMC) ElectroMagnetic Compatibility standard for radio equipment and services EN (Radio spectrum matters) Title: Electromagnetic compatibility and Radio spectrum Matters (ERM);Wideband transmission systems;data transmission equipment operating in the 2,4 GHz ISM band and using wide band modulation techniques;harmonized EN covering the essential requirements of article 3.2 of the R&TTE Directive. EN (Product safety) 12

13 Structure of EMC Electromagnetic Compatibility Emission Immunity Conducted Disturbance Radiated Disturbance Conducted Interference ESD, Burst Surge, NEMP Radiated Interference 13

14 14 Requirements according EN

15 Requirements according the standards Concept: Design:.. Function:.. EMC: Emission Burst Radiated Immunity ESD Surge LAN WLAN 230VAC Cover 15

16 16 Example of test plan

17 Programm Electrosuisse Montena EMC From the Directive to the Standards and the Concepts Process of an EMC-conform development of a printed circuit board 17

18 Basic problems of the EMC Source (Emitter) Coupling (Path) Load (Receiver) Do not generate any disturbances: Choose the right components Good concepts Shielding Do not give any disturbances to the environment: Reduce radiation Reduce conducted emission Do not get any disturbances of the environment: Protect sensors Shielding 18

19 Advantageous Quality of EMC The mechanism of EMC react similarly: Chip level Board level Device level System level Buildings 19

20 Process of an equipment design Placement of the circuits / function blocks Ground concept (Star point etc) Measures for critical" circuits Measures for critical" signals Wiring / cabling Placement of Filters Cover / case 20

21 Process of a Board Layout Placement of the components Concept for the powering (Number of Layers) Special measures for critical " Components Special measures for critical " Signals Realise filtering Rest can be done by the "Auto-Router" Control of the work 21

22 Placement: This would be nice Port Low Middle HIGH frequencies Port 22

23 Thoughts for ourtablet Power part: DC/DC Converter RAM, FLASH, Processor: High frequencies Communication ports: Filter, Cable Part of the Display: High frequencies Touchscreen, Keys: HMI Back light inverter: Cables to the lamps WLAN-Module: Radio, Antenna 23

24 Quick placement Display port µp, RAM FLASH BLI 24

25 Final Placement Display-Interface DC/DC BLI Keyboard Print WLAN- Module 25

26 26 Display

27 Process of a Board Layout Placement of the components Concept for the powering (Number of Layers) Special measures for critical " Components Special measures for critical " Signals Realise filtering Rest can be done by the "Auto-Router" Control 27

28 Powering concept of the Tablet PCB with 6 layers One layer ground All free areas on the other layers all filled with ground Metallic frame and panel between Diplay and Main board USB port & LAN port are screened 28

29 Highlighting the capacitive blocking Power Supply 29

30 Choose of the capacitor blocking C1 about µf - Elektrolyt - Close to the supply C2 about µf - Metall-Folie - Close to the supply C3 about µf - Tantal (low RS) - A few spread over the board C4 about nf - Ceramic - Close to the ICs C5 about pf - Realised by the planes of the supply - May be influenced by the structure of the board If possible use SMD capacitors 30

31 Frequency behaviour of capacitors 10 Impedanz 1/10/100n/10uF + 5mm Leiterbahn 8 10nF 1nF 6 Z [Ohm] 4 100nF // 10 // 100nF // 10µF 10µF Frequenz [MHz] 31

32 Connecting capacitors IC IC C4 C4 IC Vcc C4 GND 32

33 Process of a Board Layout Placement of the components Concept for the powering (Number of Layers) Special measures for critical " Components Special measures for critical " Signals Realise filtering Rest can be done by the "Auto-Router" Control 33

34 What are critical components? Quartz Oscillators ASICS Drivers µp High Frequencies Harmonics Steep pulse slopes High Levels HF- interferences ESD, Burst High voltage Cross talk PLL A/D-Converter Sensors OP-Amp 34

35 A simple filter GND VCC Rückseite C (10 nf) FPGA C (10 nf) Rückseite 35

36 DC/DC-Converter: Step down Characteristics: Converter has no galvanic separation Components: Switch plus controller, Choke & Diode Choke Controller 36

37 DC/DC-Converter: Version 1 Diode Switch Choke 37

38 DC/DC-Converter: What was bad? Bad capacitive blocking Bad placement of components Bad signal flow No ground layer 38

39 DC/DC-Converter: Version 2 Switch Choke Diode 39

40 DC/DC-Converter: Results 45.0 [dbuv/m] :20: Frequency [MHz] 40.0 [dbuv/m] :49: Frequency [MHz] 40

41 Process of a Board Layout Placement of the components Concept for the powering (Number of Layers) Special measures for critical " Components Special measures for critical " Signals Realise filtering Rest can be done by the "Auto-Router" Control 41

42 What are critical signals? Clock signals Video signals Fast digital signals Long lines Analogue signals In- / Output signals di/dt Power lines Lines with high currents Reset lines 42

43 Critical lines: Reflections Reflections arises by not correctly determined Signal Lines Open line Short-circuit A serial impedance at the beginning of the line reduces high frequencies and the harmonics Open line Short-circuit 43

44 Critical lines: Reflections (2) Z1 Z2 C Z3 Version 1: Z1 = 100 Ω; C = 100 pf; Z2 = 0 Ω. Z3 = Nothing Applicable for clock lines up to 20 MHz. Be careful: Check the level of the signal! Version 2: Z1 = 100 Ω; C = 100 pf; Z2 = 100 Ω. Z3 = Nothing Applicable for clock lines up to 60 MHz. Version 3: Z1 = Ferrite bead; C = 100 pf; Z2 = 0 Ω. Z3 = Nothing Applicable for Display signals: TFT-Displays Advantage: Ferrite beads have a smaller phase shift. 44

45 Critical function blocks of the Pad Power supply Good layout of the DC/DC-Converter Processor, RAM, Flash: Good placement Filtering of the clock lines Display Interface Good placement Metallic frame and plane Short cables Touch Controller and BLI Good placement, Short cables 45

46 Critical lines of the Tablet Clock lines, Address-Data-bus Serial impedances Cables to the display Filter at the connector two-layer Flex -print Cable to the touch module Antenna structure, Immunity Accu cable Torus ferrite 46

47 Result of the «Quick»-Layout Radiated Field WITHOUT cables 45.0 [dbuv/m] :27: Frequency [MHz] 47

48 Final measurement Radiated Field WITH cables 45.0 [dbuv/m] :58: Frequency [MHz] 48

49 Why you should contact us... Idea Money Yes Conform? Diverse concepts: - Elec. Circuit / System - Construction - EMC & Safety Bad luck High costs No Testing Production Description Construction Layout of the PCB Montena EMC / Electrosuisse: EMC & Safety 49

50 Our services for you... Investigations on standards Concepts for schema and layout Measurements and tests on: EMC, Radio, Acoustics, Climatic and Safety Accredited reports Support for the Technical File Support for approvals Courses 50