XRK4991A Datasheet PDF | Exar Corporation

Exar Corporation XRK4991A

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. Each output can be hardwired to one of nine delay or function configurations. The completely integrated PLL allows external load and transmission line delay effects to be canceled.

Part No.	XRK4991A
Datasheet	XRK4991A Download
Manufacturer	Exar Corporation
Description	SKEW CLOCK BUFFER
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FEATURES

FUNCTIONAL

DESCRIPTION

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). 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. 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 four FIGURE 1. BLOCK DIAGRAM OF THE XRK4991A TEST PE FB_IN PHASE CLKIN FSEL SELD0 SELD1 Select Inputs SELC0 SELC1 SELB0 SELB1 SELA0 SELA1 FREQ...