November 2006
rev 1.4
ASM5P23S04A Configurations
Device
ASM5P23S04A-1
ASM5P23S04A-1H
ASM5P23S04A-2
ASM5P23S04A-2H
ASM5P23S04A
Feedback From
Bank A or Bank B
Bank A or Bank B
Bank A or Bank B
Bank A or Bank B
Bank A Frequency
Reference
Reference
Reference
Reference
Bank B Frequency
Reference
Reference
Reference /2
Reference /2
‘SpreadTrak’
Many systems being designed now utilize a technology
called Spread Spectrum Frequency Timing Generation.
ASM5P23S04A is designed so as not to filter off the
Spread Spectrum feature of the Reference Input, assuming
it exists. When a zero delay buffer is not designed to pass
the Spread Spectrum feature through, the result is a
1500
significant amount of tracking skew which may cause
problems in the systems requiring synchronization.
Zero Delay and Skew Control
For applications requiring zero input-output delay, all
outputs must be equally loaded.
1000
REF-Input to CLKA/CLKB Delay (ps)
500
0
-30
-500
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
-1000
-1500
Output Load Difference: FBK Load - CLKA/CLKB Load (pF)
REF Input to CLKA/CLKB Delay Vs Difference in Loading between FBK pin and CLKA/CLKB pins
To close the feedback loop of the ASM5P23S04A, the FBK
pin can be driven from any of the four available output pins.
The output driving the FBK pin will be driving a total load of
7pF 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
the above graph.
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.
3.3 ‘SpreadTrak’ Zero Delay Buffer
Notice: The information in this document is subject to change without notice.
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