Conformally Coated RF Chokes Slim Down For High-Density Uses

April 12, 2004
Monolithic ICs aren't the only devices that can squeeze more performance into smaller packages. Discrete components are getting into the act too, like the 79F series of conformally coated RF chokes from J.W. Miller Magnetics. Just 0.16...

Monolithic ICs aren't the only devices that can squeeze more performance into smaller packages. Discrete components are getting into the act too, like the 79F series of conformally coated RF chokes from J.W. Miller Magnetics.

Just 0.16 in. long and 0.10 in. in diameter, these chokes have high Q levels and high-frequency performance characteristics despite their size. This makes them ideal for high-density applications like telecom, computers and computer peripherals, and electromagnetic-interference (EMI) filters. They also suit VCRs, DVD players, set-top boxes, auto navigation systems, game consoles, and other consumer electronics.

A specially formulated resin epoxy is key to the 79F series' miniaturization. So are the ferrite bobbin cores, which protect against the effects of harsh environments. The cores additionally provide a wide inductance range, from 0.10 to 470 µH between −55°C and 105°C, and a high dielectric strength rating up to 500 V rms. Minimum Q values are 35 for chokes with values of 0.10 to 1.0 µH and 40 for chokes with values of 1.2 to 470 µH.

Self-resonant frequency ratings, which are generally higher with lower-value inductances, range from 300 MHz minimum for the choke with the lowest inductance value down to 3.5 MHz for the choke with the highest inductance value. DC current ratings range from 700 to 24 mA.

The chokes use color-coded bands for easy identification. They cost $0.06 each in production quantities with availability in four to six weeks.

J.W. Miller Magneticswww.jwmiller.com (310) 515-1720

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About the Author

Roger Allan

Roger Allan is an electronics journalism veteran, and served as Electronic Design's Executive Editor for 15 of those years. He has covered just about every technology beat from semiconductors, components, packaging and power devices, to communications, test and measurement, automotive electronics, robotics, medical electronics, military electronics, robotics, and industrial electronics. His specialties include MEMS and nanoelectronics technologies. He is a contributor to the McGraw Hill Annual Encyclopedia of Science and Technology. He is also a Life Senior Member of the IEEE and holds a BSEE from New York University's School of Engineering and Science. Roger has worked for major electronics magazines besides Electronic Design, including the IEEE Spectrum, Electronics, EDN, Electronic Products, and the British New Scientist. He also has working experience in the electronics industry as a design engineer in filters, power supplies and control systems.

After his retirement from Electronic Design Magazine, He has been extensively contributing articles for Penton’s Electronic Design, Power Electronics Technology, Energy Efficiency and Technology (EE&T) and Microwaves RF Magazine, covering all of the aforementioned electronics segments as well as energy efficiency, harvesting and related technologies. He has also contributed articles to other electronics technology magazines worldwide.

He is a “jack of all trades and a master in leading-edge technologies” like MEMS, nanolectronics, autonomous vehicles, artificial intelligence, military electronics, biometrics, implantable medical devices, and energy harvesting and related technologies.

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