The problem is that the power budgets of ITE products are increasing with performance improvements, so meeting EMI standards becomes proportionally more difficult. Enter the LTM®4613 8A μModule® step-down regulator, which saves significant design time by squeezing guaranteed EMI-compliance and high performance
into a single compact package.

EMI RADIATION SOURCES
Electromagnetic waves radiate from any switching converter and its interface leads. Pulsating voltages and currents associated with the switching action of all switch mode converters from ideal sources generate and directly influence the strength of radiated electromagnetic waves.

Furthermore, parasitic devices within the converter contribute to electromagnetic radiation. Figure 2 presents a typical buck converter including parasitic inductors and parasitic capacitors of the MOSFETs.

During MOSFET switching, the energy stored in the parasitic inductor resonates with the energy stored in the parasitic capacitor. When the energy is released, the resulting voltage spike at the switch node (VSW) can be as large as twice of the input voltage, as shown in Figure 3.

As the current capability of the MOSFET increases, the energy stored in Designers of information technology and communications systems have come face-to-face with the difficult challenge of producing feature-rich, power-hungry products that comply with international EMI standards.

Prior to sale, all information technology equipment (ITE)—commonly defined as having a regulated clock signal greater than 9kHz—must meet government standards such as FCC Part 15 Subpart B in the United States, and EN55022 in the European Union. Both standards define maximum allowable radiated emission for industrial and commercial environments (Class A) and home environments (Class B).

Details are available at http://cds.linear.com/docs/LT%20Journal/LTJournal-V21N4-04-df-LTM4613-RichardYing.pdf