XRK4991A

www.DataSheet4U.com xr FEBRUARY 2005 PRELIMINARY XRK4991A REV. P1.0.2 3.3V HIGH-SPEED (85 MHZ) PROGRAMMABLE SKEW CLOCK BUFFER at the clock destination. This feature minimizes clock distribution difficulty while allowing maximum system clock speed and flexibility. FEATURES FUNCTIONAL DESCRIPTION The XRK4991A 3.3V High-Speed Low-Voltage Programmable Skew Clock Buffer offers user selectable control over system clock functions to optimize the timing of high-performance computer systems. Eight individual drivers, arranged as four pairs of user-controllable outputs, can each drive terminated transmission lines with impedances as low as 50Ω while delivering minimal and specified output skews and full-swing logic levels (LVTTL). Each output can be hardwired to one of nine delay or function configurations. Delay increments of 0.7 to 1.5 ns are determined by the operating frequency with outputs able to skew up to ±6 time units from their nominal “zero” skew position. The completely integrated PLL allows external load and transmission line delay effects to be canceled. When this “zero delay” capability is combined with the selectable output skew functions, the user can create output-tooutput delays of up to ±12 time units. Divide-by-two and divide-by-four output functions are provided for additional flexibility in designing complex clock systems. When combined with the internal PLL, these divide functions allow distribution of a lowfrequency clock that can be multiplied by two or f...