Universal clocks for communications applications

24th April 2014

Nat Bowers

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Extending the company's range of telecommunications timing products, Exar has introduced the XR811xx series of Universal Clocks. Designed for communications, audio/video and industrial applications, the devices feature a variety of output frequencies from 10MHz to 1.5GHz, with ultra-low phase noise jitter of less than 200fs.

Providing a superior performance second source option, the QFN-10 and TSSOP-8 packaged devices are footprint compatible with industry standard synthesisers. The design of Exar’s XR811xx synthesisers utilises a highly flexible delta-sigma modulator and a very wide-ranging VCO in a PLL block that has been optimised to be extremely power efficient. With a core current consumption of just 20mA, these parts dissipate 60% less power than equivalent competitive devices, providing a very compelling power efficiency benefit to system designers.

The PLL can operate from either an input system clock or a crystal and incorporates both an integer divider and a high-resolution (less than 1Hz) fractional divider for increased flexibility to generate any clock frequency. Additionally up to four different frequency multiplier settings can be stored allowing for different application configurations providing BOM savings compared to multiple synthesisers. The XR811xx family also offers a choice of LVCMOS, LVDS or LVPECL output drivers.

Exar’s Universal Clock devices deliver extremely low, sub-200fs, output phase noise jitter as integrated over a PLL loop bandwidth of 1.875-20MHz. This spans the requirements of most WAN and LAN systems and supports communications standards including: 10GHz Ethernet, 2.5 and 10GHz SONET/SDH/OTN, xDSL and PCIe, as well as many other synchronised clock system applications.

James Lougheed, Vice President, Communications Products, Exar, comments: “The XR811xx family of products with their excellent jitter performance improves on existing industry standard designs while also providing a second source. These products offer market leading power consumption performance with less than half the power consumed by competitors. Hardware engineers will appreciate the ability to use one Exar Universal Clock to replace multiple competitor devices in reducing design complexity. Adding to our Universal PMIC portfolio, Exar now offers Universal Timing and Power solutions for a wide range of applications.”

The XR811xx products are available now in RoHS compliant, green/halogen QFN10 and TSSOP8 packages as second source alternatives to existing products. Pricing is in the range of $3-7 (USD) in 1,000 unit quantities.