NB2308A

http://onsemi.com

6

Zero Delay and Skew Control

All outputs should be uniformly loaded to achieve Zero

Delay between input and output.

Figure 3. REF Input to CLKA/CLKB Delay vs.

Difference in Loading between FBK Pin and

CLKA/CLKB Pins

1500

1000

500

0

−500

−1000

−1500

−30 −25 −20 −15 −10 −5

0

5

10

1520

2530

OUTPUT LOAD DIFFERENCE: FBK LOAD − CLKA/CLKB LOAD (pF)

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.

SWITCHING WAVEFORMS

Figure 4. Duty Cycle Timing

1.4 V

1.4 V

1.4 V

Figure 5. All Outputs Rise/Fall Time

OUTPUT

2.0 V

0.8 V

2.0 V

0.8 V

3.3 V

0 V

1.4 V

1.4 V

Figure 6. Output − Output Skew

OUTPUT

OUTPUT

INPUT

OUTPUT

Figure 7. Input − Output Propagation Delay

2

2

Figure 8. Device − Device Skew

FBK_Device 1

2

2

FBK_Device 2