What You Can Takeaway
What is the difference between EMI and EMC?
What is EMC testing?
Why should you do EMC testing?
How you can aid EMC testing during design.
One can never help paying attention to what others think of you. How well you get along, even in times where social contact is so limited, or perhaps especially, is of great importance. Fitting in with your neighbors can be some of the first forms of contact that you might be curious about — how many of your conversations have they heard, or do they think your music is too loud?
The need to fit in with the neighbors is also a dilemma for PCBAs that will be installed in larger electronic systems. There are the obvious issues of ample space and the need for adequate power to operate, of course. Often overlooked during design; however, are the electrical effects of nearby circuitry on the board under design and vice versa, especially if these PCBAs are not interconnected.
Achieving a reasonable degree of balance between all of the boards and electrical devices in an area is known as EMC. And testing is a primary means of meeting this goal. Let’s clearly define what EMC testing is, why it should be done and how you can help the process during design.
EMI and EMC: What is the Difference?
EMC, which stands for electromagnetic compatibility, is probably best defined in terms of EMI. A functionally reasonable way to interpret EMI or RFI, if limited to between 9 kHz and 275 GHz, from a communications system perspective is as noise. This means that EMI is any unwanted signal (or collection of signals) that disturbs or disrupts the transmission and/or reception of information or data.
Basically, there are two sources of EMI or noise. Radiated EMI occurs through the air and conductive EMI is transferred directly through a conductor or another material. EMC is then the ability of electrical and electronic systems in close proximity to operate with minimal interference on each other’s operation.
What is EMC Testing and Why Do It?
EMC testing can be defined as follows:
EMC testing is the performance of testing regimens that evaluate the levels of EM radiation from and to your board to determine the effect on the performance of your board and the potential impact on electronics in the surrounding environment.
Why Test for EMC?
There are a number of good reasons why your boards should undergo testing for EMC; including the following:
The prevailing motivation for EMC testing is to ensure the safety of users and operators of the electronic equipment and systems of which your boards are a part.
In addition to safety, boards should be tested to find out whether they will function as designed and meet their operational objectives within their deployment environment.
Regulations and Standards
Just in case the two reasons listed above do not provide the necessary motivation to perform EMC testing, then the fact that most EMC testing is mandatory and defined by one of many standards. From a regulatory perspective, only applicable testing must be done to avoid sanction(s) for noncompliance. Applicability may be determined by manufacturer location, end-user geolocation or industry for which the board is made.
For information on EMC testing standards, see the following:
IEC 61000: Electromagnetic Compatibility (EMC) -
Part 1, Part 2, Part 3 and Part 4-16.
ISO 11452: Road Vehicles - Component Test Methods For Electrical Disturbances From Narrowband Radiated Electromagnetic Energy - Part 1 - Part 9.
How You Can Aid EMC Testing During Design
Obviously, EMC compliance can be a major development issue depending upon the type of board you are building. In fact, for the more restrictive industries (aerospace, automotive, medical devices) noncompliance is synonymous with non-usable. Therefore, we know what EMC testing is and why it should be done. The last remaining question is whether you can aid the testing process during design. The answer is yes; however, the level of assistance is dependent upon the design tool you use.
The following steps can be instituted by most design programs and can help facilitate the testing process:
Design Aids for EMC Testing
Follow good layout rules for high-speed boards
Your board layout is always important; however, there are special considerations that must be accommodated for high-speed and SPI applications.
Make good use of the stackup
For high power boards and PCBAs with switching power supplies, good filtering is critical for voltage regulation and to manage noise and achieve EMC.
Include test points
Strategically placed test points can also be helpful for bench testing of the board.
Use shielding, if appropriate
Shielding can be an asset and may be necessary for high power radiators; such as transformers.
Incorporating the above into your design will help with EMC testing. However, the best assistance is to perform EMC analysis during design. This allows you to make any necessary changes prior to having your boards built, which will save you time and costs.
Allegro Design Options
As shown above, Cadence’s advanced PCB Design and Analysis software allows you to target specific design activity or board type. Allegro has an Analog/RF option that focuses your design on board issues that are important for EMC.
If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.
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