While it is merely a nuisance to experience radio interference, it is definitely a serious matter if an ABS, stability control, or airbag suffers a malfunction because a vehicle passes a TV tower too closely. Thus, mastering EMC is a basic requirement for automotive electronics designers. Part one of this article explains basic strategies and provides useful hints.
EMC, or electromagnetic compatibility, is the ability of an electronic device (or a module, printed circuit board, or integrated circuit) to operate in an electromagnetically distorted environment while keeping its own distortions below certain thresholds so that other devices do not suffer any serious adverse effects. For many people this field of expertise seems more like a form of black magic: No matter what work is done related to EMC, not only will something completely unexpected and unpredictable happen. Worse than that, it can be assumed that things will always take a turn in the wrong direction. It will become apparent through this article whether this viewpoint is accurate and what engineers can do to gain more facility in this field.
Those involved in the field of electronics, especially in the automotive sector, will certainly have been confronted by EMC-related issues more than once. The phenomenon of radio interference is nearly as old as the invention of radio itself and at an early stage led to the definition of guidelines for noise suppression. The other part of EMC, the immunity against distortions, only began attracting attention around fifty years ago.
Not only is the number of electronic control units in cars on the rise, so too is the number of electronic devices frequently used inside the cars, such as cell phones, portable navigation devices, wireless headsets, which may also cause interference.
Making matters even worse is that more and more of devices of this kind operating at higher and higher frequencies are constantly being introduced to the market. Higher frequencies imply that smaller structures can behave like an antenna and cross-coupling needs to be considered even for relatively small coupling capacitances. It is therefore only natural that there has been a growing need to define certain rules of the game over the past decades.
Nowadays all car manufacturers are highly aware of the fact that EMC testing is an important part of car electronics development and understand that EMC issues become costlier the later they are discovered. That is the reason why they do not just rely on a final test inside the car but insist on tests of the electronic control unit (ECU) and even on test results of the integrated circuits used in the design before deployment in vehicles.
All around the world a wide variety of test methods have been developed for both unwanted electromagnetic emissions as well as the susceptibility for electromagnetic distortions. In the meantime, all integration levels are covered and over the past 10 years the various standardization committees have devoted their time to the IC level.
As a semiconductor manufacturer, Atmel is confronted primarily with IC-level and ECU-level tests. Unfortunately, not only have there been quite a large number of different standards established (perhaps a bane to testing specialists), at the same time, many OEMs apply these standards in slightly different ways.
Read this complete article here, which details EMC tests, frequency selection, and PCB layouts, courtesy of Automotive Designline Europe.
Part 2 of this feature discusses methods for suppressing high-frequency noise.
There are two SAE standards that apply to EMC. SAE J551 applies to vehicles, and SAE J1113 applies to components (modules). Both are used as a basis for internal standards by automobile manufacturers, farm machinery, heavy equipment, etc.
One of my clients claimed it meant "Even More Money for Consultants." Ouch... Incidentally, automotive EMC problems are among the most challenging we see -- low emissions, rough EMI environment, extreme cost constraints, and more. So when you finally pass the automotive EMC tests, you have done a very fine job of design!
A vehicle's ECU can be stopped functioning by a near by powerfull radiation . To safe guard this ECU and other electronic control systems need to be protected from this type of powerefull radiation. Similarly the ECU and the other electronic sub systems radiates EM waves which can interfere with other systems and the traveller in the vehicle may get effected also while the vehicle passes by others may get this radiation. This also needs to be taken care while designing.EMC requirements to be met by the manufacturers.
What are the standards, which define the EMI/EMC requirements for automobile electronics? Are they different from EN55011 (electromagnetic emission) and EN61000-4-2 (ESD),-3 (RF susceptibility),-4 (EFT),-5 (Voltage Surge)... etc. series of standards?
The reason for "EMC stand for exasperating, magic, or confusing" is that people keep thinking EMC is only one single phenomenon. When you read all these EMC articles, please remember there are two types of EMC problems: conductive and radiative
It might be noted that current efforts toward lower power consumption is being implemented in many cases by increased impedance of logic lines thus requiring lower drive current. This trend will make the logic lines more suceptable to RF interferrance. This can be overcome but requires much more attention to this subject than was needed in older designs. The twists and turns of design interplay are interesting as with higher impedances to get lower drive currents you cannot just add capacitive filtering because you need the lower drive impedance go get the speed with that added capacitance. (read it again it'll make sense)Gets fun when you find yourself partitioning your multilayer PWB into compartments to provide EM isolation inside the board before you even get to protecting yourself from the outside world.
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