Recent noise-related EMI, EMS, EMC issues have surfaced
To reduce noise, conduction and absorption of electromagnetic waves must be prevented.
It is important to identify the cause from the early stages of product development.


As technologies such as 5G, 6G, AI, IoT, AR, VR, big data, cloud, and autonomous driving develop, the demand for high-voltage electronic devices that handle high-speed signals is increasing. In addition to high performance, miniaturization is also accelerating as the application operation location is not limited to indoors or outdoors.

The trend toward higher performance and miniaturization of electronic products has presented electronic product designers with the task of solving the issue of electromagnetic noise. If electromagnetic noise cannot be effectively reduced, the product cannot even be released. However, the causes of noise are diverse, and as product development progresses, the available countermeasure technologies and methods become limited. The required costs continue to increase.

Noise must be thoroughly reviewed and evaluated from the early stages of product development to allow for the establishment of a flexible noise countermeasure. Electronic product developers must understand the types and properties of noise and be able to effectively use countermeasures appropriate for each noise and device.

We asked Song Oh-yong, a senior researcher at ROHM Korea Technical Center who is in charge of technical support for automotive semiconductor components, how engineers should approach EMI, EMC, and EMS issues related to electromagnetic noise, which are considered somewhat difficult and tricky.



Q. In the industry, electromagnetic wave-related issues in circuits are usually referred to as EMI/EMC issues. What are the exact terms and meanings of EMI, EMC, and EMS?

A. EMI is an abbreviation for 'Electromagnetic Interference', and it is the process of checking how much electromagnetic waves a developed set generates from the perspective of the electromagnetic wave generation source. EMS stands for 'Electromagnetic Susceptibility' and is the process of checking how much a developed set is affected by electromagnetic waves, or in other words, how vulnerable the set is to electromagnetic waves.

EMC is an abbreviation for 'Electromagnetic Compatibility', which means electromagnetic compatibility. In the industry, it is generally used as a term that encompasses EMI and EMS.



Q. How are electromagnetic waves usually generated and how do they spread?

A. When current flows through a wire or circuit, a magnetic field is generated. The electromagnetic waves generated at this time flow out through the wire or spread out into the air in the form of radio waves.



Q. EMC problems are said to have various causes and are difficult to identify. How should engineers analyze them? Please introduce a typical methodology.

A. EMC problems are not easily inferred because they are caused by various factors such as parasitic capacitance and transient characteristics of components or circuits. Most problems are identified through EMC-related certification tests. In the case of EMI, countermeasures are established by identifying where the relevant frequency is generated using NF (Near Field) probes, etc.



Q. When thinking of ways to reduce electromagnetic noise, shielding usually comes to mind. What are the pros and cons of shielding and what are some other methods besides shielding?

A. Shielding is a very effective way to reduce electromagnetic waves. It has the advantage of solving EMI and EMS problems at the same time, but it also has the disadvantage of increasing cost.

Other methods besides shielding include changing frequency-related settings inside the IC, adding filters that reflect and absorb electromagnetic waves, and changing the layout, etc.



Q. What devices are used to reduce noise?

A. To reduce noise, you need to block the conduction and absorption of electromagnetic waves. In the field, LC filters are mainly used to block conduction, and ferrite cores or beads are added for absorption. In addition, capacitors, varistors, or shielding cans are also used.



Q. There are many devices that have EMC issues on the PCB. Why did you choose to cover the power sector, specifically DC/DC converters, in the 9/14 webinar?

A. Power circuits are essential circuits in all electronic circuits. Recent electronic devices require high-performance and multi-functional designs compared to the past, which increases noise. Through this seminar, ROHM hopes to help electronic engineers more easily solve EMC problems when they encounter them in the power supply sector.



Q. Please introduce ROHM’s EMC-resolving products, solutions, and services.

A. ROHM has many functional products that incorporate the SSCG (Spread Spectrum Clock Generator) function in power ICs to avoid EMC-related issues, or that can operate in synchronization with an external clock. In addition, we have developed the EMS-specific “EMARMOUR™” series of products that complement conventional operational amplifiers (OP Amps) that are vulnerable to EMS due to low signal amplification, and are highly regarded in the automotive and industrial equipment markets.

In addition, we provide EMC basic content to help power design engineers establish EMC countermeasures, and we continuously provide technical support for total solutions from IC selection to circuit configuration through the responsible FAE.



More detailed information on EMC countermeasures for DC/DC converters will be available at the ROHM webinar on Tuesday, September 14 at 10:30 AM.