Sonet/SDH clock multiplier ICs yield low jitter

Austin, Texas — The latest addition to Silicon Laboratories Inc.'s family of precision clock multiplier ICs are capable of generating the ultra low jitter reference clocks required in high-speed Sonet/SDH line cards.

Based on the company's digital signal phase-locked loop (DSPLL) technology, the clock multiplier IC delivers jitter generation as low as 0.7-ps rms. This is far lower than OC-48/STM-16 jitter specifications, while requiring no external components and less than one-fifth the board space of discrete solutions, said Brad Fluke, vice president and general manager of Silicon Laboratories. “The Si5318 is the smallest, most highly integrated jitter attenuating PLL IC designed for the OC-48/STM-16 market,” he added.

Unlike competing solutions based on hybrid combinations of analog circuitry, crystals or SAW-based oscillator elements, these precision clock ICs are based on the company's patented DSPLL technology, which uses digital signal processing techniques to create a fully integrated PLL. The wide tuning range of the DSPLL enables one design to support a broad range of frequencies that would traditionally require multiple crystal or SAW-based PLLs. This frequency agility allows one Si5318 design to handle both SONET/SDH and forward error correction (FEC) rates, minimizing bill-of-material (BOM) complexity and saving R&D expense.

The device provides user-selectable loop filter bandwidths ranging from 800 Hz to 12800 kHz, allowing the user to easily match the level of jitter attenuation to the amount of clock cleaning required by the application, a feature not available with discrete PLL solutions.

The ICs generate a single output clock in the 19 or 155 MHz range from a reference input ranging in frequency from 19 to 155 MHz. The Si5318 is packaged in a 9mm x 9mm CBGA. Samples are available now with volume production available in July 2005. An evaluation board is also available for $350.

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Block Diagram of Silicon Labs' Si5318

The Si5318 precision clock multiplier ICs cost $32.00 in 1,000-piece quantities.Click here for the Si5318 data sheet.

Silicon Laboratories , 1-512-416-8500,

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