New clock generator produces multiple precision clock frequencies for networking

Analog Devices has released a new clock generator that simplifies clock design and reduces the need for oscillators in multi-standard networking and communications infrastructure systems. The AD9551 clock generator features a new, simplified architecture to produce and translate multiple precision network clock frequencies, which can replace up to five oscillators. Oscillators support forward error correction (FEC), holdover, switchover, and precise frequency generation-functions that are essential in network switches, routers, and line cards.

The AD9551 is also better in accuracy and reliability in comparison to discrete oscillators. The space saving and design time saving both are addressed by launching this product.

The AD9551 clock generator accepts one or two reference input signals and generates one or two output signals that are harmonically related by a programmable factor of 1 to 63. Precisely translating the reference frequency to the desired output frequency, it includes input receivers and output drivers that are capable of either single-ended or differential operation. On-chip reference monitoring and switchover circuitry internally synchronize the two references to prevent phase perturbations at the output in the event of a reference failure.

Should either or both references fail, the AD9551 maintains a steady output signal with no phase disturbance on the output. The device relies on an external 26-MHz crystal (nominal) and the internal digitally-compensated crystal oscillator (DCXO) of the first of two cascaded fractional-N phase-locked loops (PLLs) to provide a clean reference for the second PLL, and to hold the output frequency in case of reference failure. The second fractional-N PLL enables fine precision output frequency tuning with low phase noise. The AD9551 provides a serial-peripheral interface (SPI) port, and pin-selectable pre-set divider values that offer an assortment of frequency ratios, including all the standard rates for Gigabit Ethernet (644.53125 MHz), 10 Gigabit Ethernet (625 MHz), SONET/SDH (622.08 MHz), and Fiberchannel (657.421875 MHz) and the established FEC ratios (15/14, 239/237, 239/238, 255/237, 255/238). This clock IC operates in the temperature range of -40°C to +85°C.

Package: 40-lead LFCSP
Availability: Now in samples
Price: Each $14.75 for 1K pieces