|
楼主 |
发表于 2006-7-11 17:38:00
|
显示全部楼层
EMC Design Considerations簡介
Electromagnetic compatibility is a subject most designers did not have to worry about
a few years ago. Today, every designer putting a product on the global market has to
consider this. There are two main reasons for this:
• The electromagnetic environment is getting tougher.
High-frequency radio transmitters, like mobile telephones, are found everywhere.
More and more systems are using switching power supplies in the power circuit,
and the overall number of electronic appliances is increasing every year.
• Electronic circuits are becoming more and more sensitive.
Power supply voltages are decreasing, reducing the noise margin of input pins.
Circuit geometries get smaller and smaller, reducing the amount of energy
required to change a logic level, and at the same time reducing the amount of
noise required to alter the logic values of signals.
From a designer’s point of view, EMC phenomena have to be considered in two different
ways:
• How the environment may affect the design (immunity).
• How the design may affect the environment (emission).
Traditionally, the only government regulations have been on the emission side: An
electronic device is not allowed to emit more than a certain amount of radio frequency
energy to avoid disturbing radio communication or operation of other electronic equipment.
Most countries in the world have regulations on this topic.
Additional demands on noise immunity earlier were found only for special applications,
like medical equipment, avionics and military applications.
8-bit
Microcontroller
Application
Note
Rev. 1619C–AVR–01/04 |
|