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High-frequency crystal oscillator produces low jitter

Posted: 22 Nov 2007 ?? ?Print Version ?Bookmark and Share

Keywords:low jitter crystal oscillators? Fibre Channel? Ethernet? InfiniBand? PCIe?


Maxim Integrated Products has introduced the DS4-XO series of crystal oscillators that support frequency operation from 75MHz to 622.08MHz.

The miniature crystal oscillators provide jitter performance of less than 1psRMS (12kHz to 20MHz) over the -40C to 85C extended temperature range. Manufactured using fundamental AT-cut crystal technology with no overtone, the DS4-XO series integrates a low-noise PLL-based oscillator designed in Maxim's own SiGe process. Fifty-five percent smaller than competitive solutions, the DS4-XO series is suited for space-constrained designs used in Fibre Channel, Ethernet, 10G Ethernet, SONET/SDH, InfiniBand, GPON, BPON, PCIe, and SAS/Serial ATA applications.

The DS4-XO series' miniature 5mm x 3.2mm package incorporates thermally managed design techniques specifically targeted for high-current (65-75mA, typ), high-frequency (100MHz and above), differential-output (LVDS, LVPECL, HCSL) applications. LVDS and LVPECL output options are available for all frequencies except the 100MHz version. This frequency is generally used in PCIe applications and is provided with (differential) HCSL output type.

These crystal oscillators are highly competitive against SAW-based oscillator designs, which are manufactured in a larger, 5mm x 7mm ceramic package. Offering comparable phase-jitter performance (Unlike third-overtone oscillator designs, the DS4-XO oscillators integrate a robust, LC-PLL circuit that uses fundamental AT-cut crystals; therefore, they completely eliminate the spurious modes of operation that result in extreme frequency deviation. Moreover, the PLL-based design easily accommodates operating frequencies up to 622.08MHz and higher, if desired. In contrast, third-overtone designs provide limited frequency operation with maximum frequencies of approximately 200MHz. The standard frequencies for the DS4-XO series of crystal oscillators are: 77.76 (DS4776), 106.25 (DS4106), 125 (DS4125), 155.52 (DS4155), 156.25 (DS4156), 160 (DS4160), 212.50 (DS4212), 311.04 (DS4311), 312.50 (DS4312), 425 (DS4425), and 622.08MHz (DS4622).

The DS4-XO crystal oscillators integrate a thermal pad that ensures the safe and effective operation of the crystal element over the entire extended temperature range and also enables high-current (65mA to 75mA, typ) applications.

These devices are available in 5 x 3.2mm x 1.49mm, 10-pin, LCCC surface-mount ceramic package. Prices start at $7.39 for 1,000 units. Samples are available to speed designs.

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