Clock Oscillators Reduce EMI By As Much As 15 dBc

Two spread-spectrum clock oscillators, dubbed the SSOC5 and SSOC7, promise to provide an efficient and economic method of reducing system electromagnetic interference (EMI) at its sourcethe clock oscillator. The modulated output frequency of the SSOC5 and SSOC7 enables EMI to be reduced by as much as 15 dBc compared to fixed crystal oscillators. The spreadspectrum oscillators operate from a +3.3-VDC supply voltage. The CMOS clock generators produce a square-wave fixedoutput signal from 6.00 to 160.00 MHz and 3.60 to 220.00 MHz, respectively. The oscillators offer a load termination to 15 pF with rise and fall times to 4.0 ns (10 to 90 percent of the waveform). In addition, the SSCO5 and SSCO7 feature 25-ppm, 50-ppm, and 100-ppm frequency-stability options from 0 to +70C. A 40-to-+85C option also is available. The use of a spread-spectrum clock oscillator at the design and development stage will negate the need for expensive EMI reduction techniques, such as filtering components, shielding enclosures, and multiple ground and power planes. The SSCOC5, which measures 5.0 x 3.2 x 1.2 mm, is available in a 4-pin SMD package. The SSOC7 is available in a 4-pin SMD package with dimensions of 7.0 x 5.0 x 1.8 mm.

Precision Devices, Inc., 8840 N. Greenview Dr., Middleton, WI 53562; (800) 274-9825, Internet: www.pdixtal.com.

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