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Volume 41 (May 18, 2005)

Reducing Digital Device Noise with World-Recognized EMC Technology (1/2)

EMC technology: The key to reducing noise in electronic devices

Today we find ourselves surrounded by an increasing number of digital devices that have proliferated as a result of the development of the Internet, the diffusion of mobile phones and digital consumer electronics, and the introduction of IT in the automotive field. Although these digital devices have brought us unprecedented convenience and comfort, they also have their share of problems, including electromagnetic interference (electromagnetic energy emanating from one device and causing degraded performance in another). With regulations currently being established in each nation, electromagnetic compatibility (EMC) technology is drawing a great deal of attention (Figure 1). This technology is used to control electromagnetic interference (EMI) and improve electromagnetic susceptibility (EMS). Digital device manufacturers therefore find themselves faced with the challenge of developing products that are capable of preventing EMI-generated noise to the greatest extent possible and that are not easily affected by EMI noise from outside sources.

In 2002, NEC Electronics (then NEC) surged past its competitors to develop an EMI measurement method specifically for use with semiconductors. By performing non-contact measurement of an LSI chip's power line current, a designer can estimate with an extremely small degree of error the EMI level of a device when an LSI chip is in actual use. This technology is referred to as the Magnetic Probe Method (MP Method), and has been established as an international standard by the International Electrotechnical Commission (IEC) (Figure 2). NEC Electronics also has surpassed the competition by developing technology for use at the design stage with LSI chips that simulate EMI noise, as well as a countermeasure technology that can be used to realize low EMI. Up until about 10 years ago, however, EMC technology did not even exist, and having to implement measures against EMI noise was not even necessary.

The rush to develop EMI countermeasures

In the mid-1990s, significant advancements were made in the acceleration and miniaturization of LSI chips. The miniaturization of processes from 0.5 µm to 0.35 µm and then down to 0.25 µm spurred the trend toward smaller-scale digital devices with higher levels of performance. Meanwhile, the development of the Internet led to the rapid advancement of networking systems within offices. It was from this time on that EMI noise started causing problems such as operating interference (electromagnetic energy emanating from one device and causing degraded performance in another) and performance malfunctions.

In reflecting back on this time, Takeshi Watanabe (team manager from NEC Electronics' Technology Foundation Development Operations Unit) commented, "It was known that digital devices generated EMI. But at the time, we did not know why." It was eventually determined that there were multiple causes. Although it was thought that perhaps LSI chips were one of these causes, electromagnetism could even be amplified by printed circuit boards. In addition, with printers and other such devices, long connection cables act as antennas, thereby generating EMI and causing malfunctions to occur in other devices in the same vicinity. Device manufacturers found themselves agonizing over how to devise a solution to these problems. The use of traditional methods to place EMI-prevention components such as EMI filters and decoupling capacitors on circuit boards would make the miniaturization of products rather difficult. Furthermore, increasing the number of components would lead to mounting costs.

In 1996, developers found themselves faced with an even more severe situation. When the EMC Directive came into effect, one of the regulations was that all electronic devices for export from Japan to European member nations would be required to meet both EMI and EMS international standards. Naturally, this meant that countermeasures would also have to be developed for LSI products. Up until that point, LSI development had been entirely focused on acceleration and miniaturization, as well as the advancement of technological innovations. But now an invisible obstacle, EMI noise, was standing in the way of further development.

In 1997, Watanabe found himself at the center of NEC Electronics' EMC project, which was the first project of its kind to be launched by the industry in Japan. For the next several years, participants collaborated with colleagues from NEC's Central Research Laboratory and devoted themselves entirely to developing an EMC measurement method, simulation technology and countermeasure technology for LSI chips. Watanabe recalls, "At the beginning, we hadn't the foggiest idea how we should go about measuring EMI. We found ourselves literally groping blindly in the dark." Finally, in 2003, NEC's three primary EMC technologies (measurement technology, simulation technology and countermeasure technology) were put to practical use, and the MP Method-the core measurement technology-became an international standard. One after another, electronics-related magazines and trade journals began covering this new method. Within no time at all, NEC Electronics' success in the development of EMC technology became recognized throughout the industry.

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