NB2308A
Zero Delay and Skew Control
All outputs should be uniformly loaded to achieve Zero
Delay between input and output.
1500
1000
500
0
−500
−1000
To close the feedback loop of the NB2308A, the FBK pin
can be driven from any of the eight available output pins.
The output driving the FBK pin will be driving a total load
of 7 pF plus any additional load that it drives. The relative
loading of this output (with respect to the remaining outputs)
can adjust the input−output delay. This is shown in Figure 3.
For applications requiring zero input−output delay, all
outputs including the one providing feedback should be
equally loaded. If input−output delay adjustments are
required, use the above graph to calculate loading
differences between the feedback output and remaining
outputs. For zero output−output skew, be sure to load outputs
equally.
−1500
−30 −25 −20 −15 −10 −5 0 5 10 15 20 25 30
OUTPUT LOAD DIFFERENCE: FBK LOAD − CLKA/CLKB LOAD (pF)
Figure 3. REF Input to CLKA/CLKB Delay vs.
Difference in Loading between FBK Pin and
CLKA/CLKB Pins
SWITCHING WAVEFORMS
1.4 V
t1
t2
1.4 V
1.4 V
Figure 4. Duty Cycle Timing
OUTPUT
2.0 V
0.8 V
t3
2.0 V
0.8 V
t4
3.3 V
0V
Figure 5. All Outputs Rise/Fall Time
OUTPUT
1.4 V
OUTPUT
t5
1.4 V
Figure 6. Output − Output Skew
VDD
2
INPUT
VDD
OUTPUT
2
t6
Figure 7. Input − Output Propagation Delay
FBK_Device 1
FBK_Device 2
VDD
2
t7
VDD
2
Figure 8. Device − Device Skew
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