Electronic Design

Conformally Coated RF Chokes Slim Down For High-Density Uses

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 Magnetics
(310) 515-1720

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