Figure: Surface-mount EMI filters

Conducted EMI refers to high-frequency noise currents that are emitted during the normal operation of electrical and electronic devices such as SMPS, motors, drilling machines, and other devices and can travel through the power lines or signal lines and interfere with the operation of other connected devices. The noise currents can also cause the lines to behave as untended antennas, leading to radiated emission from the lines that may interfere with the operation of other nearby devices in the surrounding environment.   

Surface-mount EMI Filters are designed to be directly mounted onto a printed circuit board (PCB) surface to filter out high-frequency noise (conducted EMI) on power and signal lines. These EMI filters act as low-pass filters, suppressing high-frequency noise currents while allowing desirable low-frequency signals (DC or AC) to pass through. The noise signals are directed to the ground, protecting the electrical and electronic equipment from both conducted and radiated EMI. This ensures the equipment’s electromagnetic compatibility (EMC), meaning it can function properly without disturbing other nearby devices.

Surface-mount EMI Filters are available in various circuit configurations, including Pi, T, and feedthrough filter circuits. They come with several features, such as superior filtering capabilities, the ability to withstand transient voltages and surges, exceptional solderability, resistance to solder heat, and various body sizes (e.g., 0603, 0805, 1205, and 1806). These filters are ideal for use in telecommunication equipment, cellular telephones & base stations, electronic automotive equipment, industrial electronic interfaces or programmable controllers, computer and peripheral equipment, data lines, and more.