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Clock and Data Distribution Products Pt1 Slide 11

The phase noise and jitter performance of an onsemi crystal oscillator and a competitor’s Surface Acoustic Wave, or SAW, based oscillator are compared on this slide. SAW based oscillators have a much higher price than crystal oscillators. When comparing phase noise between devices, it is important to use the same carrier frequency for both devices; both devices shown on this slide generate 312.5 MHz. The carrier frequency is at the leftmost point of the plots. The positive, right-hand side power spectral density curve can be seen on the plots. The negative, left-hand side power spectral density is not considered. Because only half of the power spectral density curve is considered, the integration range cannot have an upper bound that is greater than the carrier frequency divided by two. Using an integration range of 10 Hz to 40 MHz from the carrier frequency, a phase RMS jitter of 775 fs is obtained for the onsemi crystal oscillator and 2.15 ps for the competitor’s higher priced SAW based oscillator. In terms of the phase noise, the onsemi device has lower phase noise close-in to and far from the carrier, but the SAW based oscillator beats the onsemi crystal oscillator in the mid-range. Another important piece of information is the noise floor of the devices. The onsemi crystal oscillator has a lower noise floor at -158 dBc per Hertz, the competitor’s SAW based oscillator has a higher noise floor at -149 dBc per Hertz, but reaches this noise floor closer to the carrier frequency.

PTM Published on: 2014-08-04