XRK4991A Datasheet, PDF (6/13 Pages) Exar Corporation – 3.3V HIGH-SPEED (85 MHZ) PROGRAMMABLE SKEW CLOCK BUFFER

XRK4991A
PRELIMINARY
3.3V HIGH-SPEED (85 MHZ) PROGRAMMABLE SKEW CLOCK BUFFER
FIGURE 3. TYPICAL OUTPUTS WITH FB_IN CONNECTED TO A ZERO-SKEW OUTPUT ^[4]
xr
REV. P1.0.2
FB_IN
SELA-QA[1:0]
SELB-QB[1:0]
(N/A)
LL
LM
LH
ML
MM
MH
HL
HM
HH
(N/A)
(N/A)
SELC-QC[1:0] ^CLKIN
SELD-QD[1:0]
LM
-6t_U
LH
-4t_U
(N/A)
-3t_U
ML
-2t_U
(N/A)
-1t_U
MM
0t_U
(N/A)
+1t_U
MH
+2t_U
(N/A)
+3t_U
HL
+4t_U
HM
+6t_U
LL/HH DIVIDED
(N/A)
HH INVERT
NOTES:
4. FB_IN connected to an output selected for "zero" skew (i.e. SELx1 = SELx0 = MID).
TEST MODE
The TEST input is a three-level input. In normal system operation, this pin is connected to ground, allowing the
XRK4991 to operate as explained briefly above (for testing purposes, any of the three-level inputs can have a
removable jumper to ground, or be tied LOW through a 100Ω resistor. This will allow an external tester to
change the state of these pins.)
If the TEST input is forced to its MID or HIGH state, the device will operate with its internal phase locked loop
disconnected, and input levels supplied to CLKIN will directly control all outputs. Relative output to output
functions are the same as in normal mode.
In contrast with normal operation (TEST tied LOW). All outputs will function based only on the connection of
their own function select inputs (SELx[1:0]) and the waveform characteristics.
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