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Exar clocks offer improved skew performance

Posted: 12 Mar 2004 ?? ?Print Version ?Bookmark and Share

Keywords:exar? clock? xrk4991? xrk4991a? xrk49911?

Taking advantage of its knowledge on analog and Phase Lock Loop (PLL) design, Exar Corp. has developed a series of clock and timing devices targeted at wireless basestations, network switches, and routers.

Sergis Mushell, clock product line strategic marketing manager, said, "Exar's new devices are ideal for future 3.3V or 2.5V platforms where there is a need for the pin and functional-compatible programmable skew clocks."

While regulating data transmissions or executing system instructions, clocks produce precisely timed and repeated impulses that synchronize the overall system or other embedded applications. The company noted that driving the need for better performing clocks are faster processors, faster memory, and increasingly lower voltage requirements.

Keeping pace with these trends has put new demands on clocks for lower jitter, better skew specifications and unprecedented device reliability, Exar added.

250ps skew control

The XRK499x portfolio of 3.3V and 2.5V programmable skew clocks consists of five different products that offer faster speed, and better jitter and skew performance in different packaging sizes.

Each device incorporates four pairs of programmable skew and zero propagation delay outputs that provide timing delays. Its skew control is also guaranteed to be as low as 250ps, with selectable skew between outputs from 750ps to 18ns.

The clocks feature flexible output functions which, when combined with the internal PLL, enable transmission of low-frequency clock impulses that can then be multiplied by a factor of two or four at the clock's destination.

According to the company, designers no longer have to contend with layout and/or clock tree redesigns to support industry-changing system voltage requirements as customers do not have to carry two programmable skew clock inventories for 3.3V or 2.5V applications.

The XRK4991 and XRK4991A are housed in 32-pin packages, feature a frequency range of 3.75MHz to 100MHz with four bank skew, and are available with 250-, 500-, or 750ps accuracy. The XRK49911 has a 3.75MHz to 200MHz frequency range with 250ps accuracy, and the XRK4993 is offered in a 28-pin package and has a 3.75MHz to 100MHz frequency range with three bank skew and 250-, 500- or 750ps accuracy. The XRK4999 features a 32-pin package for either 3.3V or 2.5V, a redundant input clock, and a 3.75MHz to 200MHz frequency range with a four bank skew and 250ps accuracy.

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