Spread Spectrum Clock Oscillators from Precision Devices

2nd June 2009

ES Admin

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Precision Devices has announced the introduction of two new spread spectrum clock oscillators, the SSOC5 and SSOC7. The new SSOC5 and SSOC7 provide an efficient and economic method of reducing system EMI at its source, the clock oscillator. The modulated output frequency of the SSOC5 and SSOC7 enables EMI to be reduced by up to 15dBc relative to fixed crystal oscillators. The SSOC5 and SSOC7 operate with a 3.3V supply voltage and the CMOS clock generator produces a square-wave fixed output frequency range from 6.00MHz to 160.00MHz and 3.6MHz to 220.00MHz respectively.

A spread spectrum crystal clock oscillator is an oscillator that has the output frequency modulated in order to reduce EMI on the output signal. Frequency sources such as quartz crystal oscillators, phase lock loop (PLL) synthesisers and other types of clock signal generation are a major source of EMI in electronic circuits. 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 advantages of using low EMI spread spectrum oscillators are simplified regulatory testing, shorter time-to-market and reduced system costs.

Precision Devices specifies a load termination of 15pF maximum with rise and fall times of 4.0ns maximum (10% to 90% of the waveform). The new SSCO5 and SSCO7 offer a ±25ppm, ±50ppm and ±100ppm frequency stability option over an operating temperature range of 0°C to +70°C with a -40°C to +85°C option available.

The SSCOC5 is available in a 4-pin SMD package with dimensions of 5.0mm (l) x 3.2mm (w) x 1.2mm (h) and the SSOC7 is available in a 4-pin SMD package with dimensions of 7.0mm (l) x 5.0mm (w) x 1.8mm (h). Typical applications include office equipment, computer systems, telecommunications, set top boxes and embedded systems.