UG-169
Evaluation Board User Guide
Rev. 0 | Page 10 of 12
Charge Pump Window
0
91
71
-0
20
Figure 19. Charge Pump Window
The
Charge Pump Setup
window shown in Figure 19 is
accessed by clicking the
CHARGE PUMP
box in Figure 17.
This window is most often used to vary the charge pump
current.
CHANNEL DIVIDER WINDOW
0
91
71
-0
21
Figure 20. Channel Divider Window
The channel divider window shown in Figure 20 is accessed by
clicking the appropriate channel divider (see Figure 21) in the
main window in Figure 6. It is usually sufficient to change only
the divide ratio, because the evaluation software and the
AD9523 duty cycle correction feature ensure that the output
duty cycle remains very close to 50%.
09171
-027
Figure 21. Channel Divider
You can also vary the phase offset by changing the phase offset
bits setting under the
Divider Phase
box in Figure 20. However,
for the new phase to take effect, the SYNC signal must be
toggled, by clicking the SYNC button shown in
and
selecting
Strobe SyncB
.
0
9
171-
025
Figure 22. Toggling SYNC Signal
OUTPUT DRIVER WINDOW
0
91
71
-0
22
Figure 23. Output Driver Window
The output driver window shown in Figure 23 is accessed by
clicking any of the triangular output driver symbols on the right
side of the main window (see Figure 24).
0
917
1-
026
Figure 24. Output Drivers
It is important to power down unused outputs on the evaluation
board, because they can be a major source of unwanted spurs.
The outputs are ac-coupled with 100 Ω differential resistors on
each output. This termination scheme is ideal for LVPECL
drivers. However, this scheme degrades the CMOS driver
performance. Improved CMOS driver performance is achieved
by removing the 100 Ω resistors.
