Fundamentals of EMI-EMC and its industrial growth in commercial market
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Fundamentals of EMI-EMC and its industrial growth in commercial market
- 1. Fundamentals of EMI & EMC and its Industrial Growth in Commercial Market Dr.R .Lenin Raja M.E., Ph.D., EMC Specialist – Delhi NCR General Manager – BTH Group of Labs Member – EMC Experts Contact : 91-8870082081 7/31/2017 PSNA -BEMT Guest Lecture 1
- 2. Overview Introduction EMI & EMC-Hazards Electromagnetic – Environment EMC Design Process Commercial Requirement Industrial Growth Conclusion 7/31/2017 PSNA -BEMT Guest Lecture 2
- 3. Introduction 7/31/2017 PSNA -BEMT Guest Lecture 3
- 4. Electromagnetic Compatibility [EMC] Electromagnetic Emissions Your System Cannot Interfere With Other Systems or Subsystems in the Vehicle (e.g., FM Radio). Electromagnetic Susceptibility Your System Must Continue to Operate Correctly in the Presence of Interference From Others or Transient Disturbances. 7/31/2017 PSNA -BEMT Guest Lecture 4
- 5. ELECTROMAGNETIC INTERFERENCE [EMI] Conducted Interference Enters/Exits on Wires for Power or Control Radiated Interference Enters/Exits Through the Air Emissions Must be Controlled to Protect: AM & FM Radio Stations Aircraft Communications & Navigation Emergency Services Land Communications 7/31/2017 PSNA -BEMT Guest Lecture 5
- 6. Electromagnetic Compatibility EMC EMI EMS EMI – Conducted Emission ( i.e Cable) - Radiated Emission (i.e Air) EMS – Conducted Susceptibility - Radiated Susceptibility Standards followed as per CISPR, IEC, EN, FCC & IC 7/31/2017 PSNA -BEMT Guest Lecture 6
- 7. Electromagnetic Interference 7/31/2017 PSNA -BEMT Guest Lecture 7
- 8. Electromagnetic Interference 7/31/2017 PSNA -BEMT Guest Lecture 8
- 9. EMI & EMC-Hazards 7/31/2017 PSNA -BEMT Guest Lecture 9
- 10. Electromagnetic Spectrum 7/31/2017 PSNA -BEMT Guest Lecture 10
- 11. Electromagnetic Spectrum – Hazards 7/31/2017 PSNA -BEMT Guest Lecture 11
- 12. Electromagnetic Spectrum- Hazards 7/31/2017 PSNA -BEMT Guest Lecture 12
- 13. Electromagnetic Spectrum- Hazards 7/31/2017 PSNA -BEMT Guest Lecture 13
- 14. Electromagnetic – Environment 7/31/2017 PSNA -BEMT Guest Lecture 14
- 15. Electromagnetic Interference – Environment 7/31/2017 PSNA -BEMT Guest Lecture 15
- 16. Electromagnetic Interference – Environment 7/31/2017 PSNA -BEMT Guest Lecture 16
- 17. Electromagnetic Interference – Environment 7/31/2017 PSNA -BEMT Guest Lecture 17
- 18. Electromagnetic Interference – Environment 7/31/2017 PSNA -BEMT Guest Lecture 18
- 19. Electromagnetic Interference – Environment 7/31/2017 PSNA -BEMT Guest Lecture 19
- 20. Electromagnetic Interference – Environment 7/31/2017 PSNA -BEMT Guest Lecture 20
- 21. The Evolution of EM Noise Radio and TV: Before 1984 three TV programs were broadcasted in Germany. With the advent of cable and satellite TV the number of programs (not their quality) exploded. New territories in the EM spectrum were occupied. Why has EMC more and more become an issue in the past decades? It is interesting to look at the evolution of randomly selected EM subjects: Telecommunication: This telephone inside the DESY tunnel must be from the 1960s when only Big Bosses had “mobile” phones installed in their cars. Today we have the atmosphere filled with EM smog from cell phones, WLAN etc. But imagine the ionizing radiation hardness of this black thing
- 22. Contd., Automotive: My 1977 beetle had the following electric parts: battery, generator, ignition system, lamps, horn, rear window heating, radio. Nowadays almost everything is operated electrically and there are many intelligent assistant systems: A modern Fiat Panda has more computing power embedded than the DESY computing center of 1977 (IBM 370/168). Cars are among the toughest EMI places. Power supply: For a long time the majority of loads in the power grid was linear, i.e. composed of R, C, L. Today’s switched power supplies are energy-efficient but leave a lot of noise in the mains due to their pulsed current consumption. 7/31/2017 PSNA -BEMT Guest Lecture 22
- 23. EMC Environment: Susceptibility Power Transients Inductive Load Switching Voltage Sag “Load Dump” RF Immunity On-Board Transmitters Radio Stations Airport Radar Systems Sensors are Most Vulnerable Electrostatic Discharge (ESD) Up to 15kV 7/31/2017 PSNA -BEMT Guest Lecture 23
- 24. EMC Design Process 7/31/2017 PSNA -BEMT Guest Lecture 24
- 25. The design process System architecture the structure and details – EMC -How many layers in PCBs? -Are reactive circuits located away from I/O ports? -Are I/O ports isolated/shielded? -Are IC families appropriate for speeds needed? -Will housing provide shielding? 7/31/2017 PSNA -BEMT Guest Lecture 25
- 26. Design for compliance Initial Design must consider the following: design goals Components PCB architecture PCB layout and I/O Cables enclosures and shielding software/firmware 7/31/2017 PSNA -BEMT Guest Lecture 26
- 27. The design process Design rulesthe circuit and layout constraints –EMC - Are RF signal traces short and/ or embedded? - Are bypass caps located and sized optimally? - Are ground planes low-Z, and earth bypass provided? - Have sensitive designs been modeled? -Consider use of Signal Integrity and Quiet expert, EMC Flo simulation tools 7/31/2017 PSNA -BEMT Guest Lecture 27
- 28. Design for compliance: software and firmware Design for robustness: - checkpoint routines and watchdog timers. - checksums, error detection/correction codes. - “sanity checks” of measured values. - poll status of ports, sensors, actuators. - read/write to digital ports to validate. 7/31/2017 PSNA -BEMT Guest Lecture 28
- 29. The design process To increase the EMC success rate, the design process must have following checks: -Be sure the regulatory specifications are correct and current. -Take into account the impact of equipment architecture on EMC. Assure that purchased modules also comply. - Consider EMC design rules, manual and/or automatic. - Include places for EMC compliance modifications. - Perform pre-compliance testing where possible. 7/31/2017 PSNA -BEMT Guest Lecture 29
- 30. The design process Regulatory evaluation is it legal? If not modify – EMC - Were places provided for optional filtering/bypassing? - Are ferrites cost-effective? - Can spring fingers be added to the enclosure? - Will a shielded cable help? - Board re-spin? 7/31/2017 PSNA -BEMT Guest Lecture 30
- 31. Design for compliance: logic families EMI increases with power consumption EMI increases with slew rate/clock speed EMI increases with ground bounce EMI increases with output loading Differential drive can reduce EMI (LVDS) 7/31/2017 PSNA -BEMT Guest Lecture 31
- 32. Design for compliance: PCB architecture Adjacent ground and power planes act as very good decoupling capacitors. ground and power planes can shield high-speed or low-level signal traces between. separate ground and chassis planes can reduce noise. 16-planes (layers) design is common for back planes 7/31/2017 PSNA -BEMT Guest Lecture 32
- 33. Design for compliance : reduce emissions • Short straight current elements radiate fields that are: – Proportional to the current they carry (l) – Proportional to their (electrical) length (L) – Increasing with frequency (f) • Small current loops radiate fields that are: – Proportional to the current – Proportional to the square of the loop radius -- and the square of frequency (E,H) ~ (f, L, l) (E,H) ~ (f2, a2, l) L I a I 7/31/2017 PSNA -BEMT Guest Lecture 33
- 34. Design for compliance Clock Clock Buffer I/O Driver EdgeConnector • Locate I/O drivers away from sources of high frequency and near the connectors they serve. 7/31/2017 PSNA -BEMT Guest Lecture 34
- 35. Common Mode and Differential Signals • Differential Signals: • Convey the desired information • Don’t cause interference: The fields generated by differential currents oppose each other and nearly cancel. • Common Mode Signals: • Are the major source of cable radiation • Have no useful purpose • Cause the cabling to act as a monopole antenna Vcm 7/31/2017 PSNA -BEMT Guest Lecture 35
- 36. Design for compliance: Shielding 7/31/2017 PSNA -BEMT Guest Lecture 36
- 37. Design for compliance: enclosure openings Radiated Signal 7/31/2017 PSNA -BEMT Guest Lecture 37
- 38. Design for compliance: aperture size and shielding effectiveness 7/31/2017 PSNA -BEMT Guest Lecture 38
- 39. Design for compliance: shielding of I/O, using chassis Incorrect Chassis Ground Correct Signal Ground 7/31/2017 PSNA -BEMT Guest Lecture 39
- 40. Test for Compliance pre-compliance EMI site pre-compliance tools 7/31/2017 PSNA -BEMT Guest Lecture 40
- 41. To pre-test for RF immunity: use licensed transmitters for radiated fields. use coupling networks and transformers for conducted disturbances. To mitigate RF immunity problems: try ferrites and spring fingers above 50 MHz try filters below 50 MHz, bypassing anywhere. Pre-compliance tools 7/31/2017 PSNA -BEMT Guest Lecture 41
- 42. Pre-compliance EMI sites 1 m site minimizes factory ambient. good for small EUT, frequencies > 100 MHz. Screened Room inexpensive, OK for regulatory conducted emissions and conducted immunity tests. can be used for radiated emissions, with precautions. 7/31/2017 PSNA -BEMT Guest Lecture 42
- 43. Pre-compliance EMI site Pre-Compliance test setup: EUT 1 m analyzer floor - not a ground plane 7/31/2017 PSNA -BEMT Guest Lecture 43
- 44. Pre-compliance tools Immunity disturbance generators (ESD, surge…) radio transmitters ferrites filters and filtered connectors 7/31/2017 PSNA -BEMT Guest Lecture 44
- 45. Pre-compliance tools EMI cable manipulation – ferrites – filters and filtered connector EMI probes 7/31/2017 PSNA -BEMT Guest Lecture 45
- 46. Pre-compliance testing: EMI probes 50 cable to analyzer 39 pF capacitor on center conductor contact probe Contact probes are useful in finding: - reactive component pins - reactive PC board traces and planes - reactive I/O and connector pins - driven areas of enclosures 7/31/2017 PSNA -BEMT Guest Lecture 46
- 47. Pre-compliance testing: EMI probes proximity probe50 cable to analyzer center conductor looped back to shield and soldered Proximity probes are useful in localizing: - reactive PC board areas and components - reactive signal, I/O and power cables - reactive enclosure gaps and openings - by pumping signal in, as immunity probe 7/31/2017 PSNA -BEMT Guest Lecture 47
- 48. CB radio 27 MHz Portable phone handset 49 MHz /2500 MHz Garage door opener 300 MHz Walkie-talkie 460 MHz Cell phone, analog/TDMA 900 MHz Cell phone, PCS 1900 MHz Wireless LAN 2450 MHz Pre-compliance testing: radio transmitters 7/31/2017 PSNA -BEMT Guest Lecture 48
- 49. Commercial Requirement 7/31/2017 PSNA -BEMT Guest Lecture 49
- 50. Electromagnetic Compatibility Immunity Standards IEC 61000-3-2 : Harmonics Emission IEC 61000-3-3 : Flicker & Fluctuations IEC 61000-4-2 : Electro Static Discharge IEC 61000-4-3 : Radiated Susceptibility IEC 61000-4-4 : Electric Fast Transient IEC 61000-4-5 : Surge Immunity IEC 61000-4-6 : Conducted Susceptibility IEC 61000-4-8 : Power Frequency Magnetic Field IEC 61000-4-10: Damped Oscillatory Wave IEC 61000-4-11: Voltage Dips & Interruption…..etc., CISPR, EN, FCC, IEC & IC, CCC, CE mark, S Mark, and ISI Mark 7/31/2017 PSNA -BEMT Guest Lecture 50
- 51. Indian Marking & Certifications 7/31/2017 PSNA -BEMT Guest Lecture 51
- 52. International Marking & Certifications 7/31/2017 PSNA -BEMT Guest Lecture 52
- 53. Industrial Growth 7/31/2017 PSNA -BEMT Guest Lecture 53
- 54. Contd., 7/31/2017 PSNA -BEMT Guest Lecture 54
- 55. Contd., 7/31/2017 PSNA -BEMT Guest Lecture 55
- 56. Contd., 7/31/2017 PSNA -BEMT Guest Lecture 56
- 57. Conclusion ? 7/31/2017 PSNA -BEMT Guest Lecture 57
- 58. Dr.R .Lenin Raja M.E., Ph.D (RF & Antenna) EMC Specialist – Delhi NCR General Manager – BTH Group of Labs Member – EMC Experts Contact : 91-8870082081 leninaucbe@gmail.com emclab@bharattesthouse.com My profile 7/31/2017 PSNA -BEMT Guest Lecture 58
Editor's Notes
- We generally think of signals propagating through our circuits in one of three modes, single-ended, differential mode, or common mode. Single ended mode is the mode we are most familiar with. It involves a single wire or trace between a driver and a receiver. The signal propagates down the trace and returns through the ground system. Differential mode involves a pair of traces (wires) between the driver and receiver. We typically say that one trace carries the positive signal and the other carries a negative signal that is both equal to, and the opposite polarity from, the first. Since the signals are equal and opposite, there is no return signal through ground; what travels down one trace comes back on the other. Common mode signals are typically more difficult to understand. They may involve either single-ended traces or two (or perhaps even more) differential traces. The SAME signal travels along both the trace and its return path (ground) or along both traces in a differential pair. Most of us tend to be unfamiliar with common mode signals because we tend never to intentionally generate them ourselves. They are usually the result of noise being coupled into the circuit from some other (nearby or external) source. Generally, their consequences are neutral, at best, or damaging at worst. Common mode signals can generate noise that interrupts the operation of our circuits, and are a common source of EMI problems. Advantages: Differential signals have one obvious disadvantage over single-ended signals. They require two traces instead of one, or twice as much board area. But there are several advantages to them. If there is no return signal through ground, then the continuity of the ground path becomes relatively unimportant. So if we have, for example, an analog signal going to a digital device through a differential pair, we don’t have to worry about crossing power boundaries, plane discontinuities, etc. Separation of power systems can be made easier with differential devices. Differential circuits can be very helpful in low signal level applications. If the signals are VERY low level, or if the signal/noise ratio is a problem, then differential signals effectively double the signal level (+v – (-v) = 2v). Differential signals and differential amplifiers are commonly used at the input stages of very low signal level systems. Differential receivers tend to be sensitive to the difference in the signal levels at their inputs, but they are usually designed to be insensitive to common-mode shifts at the inputs. Therefore, differential circuits tend to perform better than single- ended ones in high noise environments. Switching timing can be more precisely set with differential signals (referenced to each other) than with single-ended signals (referenced to a less precise reference signal subject to noise at some other point on the board.) The crossover point for a differential pair is very precisely defined (Figure 1). The crossover point of a single ended signal between a logical one and a logical zero (for example) is subject to noise, noise threshold, and threshold detection problems, etc. Key Assumption: There is one very important aspect to differential signals that is frequently overlooked, and sometimes misunderstood, by engineers and designers. Let’s start with the two well-known laws that (a) current flows in a closed loop and (b) current is a constant everywhere within that loop. Consider the “positive” trace of a differential pair. Current flows down the trace and must flow in a loop, normally returning through ground. The negative signal on the other trace must also flow in a loop and would also normally return though ground. This is easy to see if we temporarily imagine a differential pair with the signal on one trace held constant. The signal on the other trace would have to return somewhere, and it seems intuitively clear that the return path would be where the single ended trace return would be (ground). We say that, with a differential pair, there is no return through ground NOT because it can’t happen, BUT because, the returns that do exist are equal and opposite and therefore (sum to zero and) cancel each other out. This is a VERY important point. If the return from one signal (+i) is exactly equal to, and the opposite sign from, the other signal (-i), then their SUM (+i –i) is zero, and there is no current flowing anywhere else (and in particular, though ground). Now assume the signals are not exactly equal and opposite. Let one signal be +i1 and the other be –i2 where i1 and i2 are similar, but not equal, in magnitude. The sum of their return currents is (i1 – i2). Since this is NOT zero, then this incremental current must be returning somewhere else, presumably ground. So what, you say? Well let’s assume the sending circuit sends a differential pair of signals that are exactly equal and opposite. Then we assume they will still be so at the receiving end of the path. But what if the path lengths are different? If one path (of the differential pair) is longer than the other path, then the signals are no longer equal and opposite during their transition phase at the receiver (Figure 2). If the signals are no longer equal and opposite during their transition from one state to another, then it is no longer true that there is no return signal through ground. If there is a return signal through ground, then power system integrity DOES become an issue, and EMI may become a problem. Design Rule 1: This brings us to our first design guideline when dealing with differential signals: The traces should be of equal length. There are some people who argue passionately against this rule. Generally, the basis for their argument involves signal timing. They point out in great detail that many differential circuits can tolerate significant differences in the timing between the two halves of a differential signal pair and still switch reliably. Depending on the logic family used, trace length difference of 500 mils can be tolerated.
- Capacitor can block DC going into Analyzer