Evaluation Board User Guide
UG-077
Rev. 0 | Page 11 of 16
CHARGE PUMP WINDOW
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Figure 17. AD9522 Charge Pump Window
The
Charge Pump Setup
window shown in Figure 17 is
accessed by clicking the
CHARGE PUMP
box on the main
window. This window is most often used to vary the charge
pump current.
The window also has a check box for setting the charge pump
voltage to V
CP
/2, which is very useful for debugging the PLL and
isolating the output driver section of the AD9522 from the PLL
section.
ZERO DELAY WINDOW
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Figure 18. AD9522 Zero Delay Window
The zero delay window shown in Figure 18 is accessed by
clicking the
ZERO DELAY
box on the main window.
When internal zero delay mode is selected, the window shrinks
because only Divider 0 can be selected in that mode.
VCO CALIBRATION WINDOW
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Figure 19. AD9522 VCO Calibration Window
The VCO calibration window shown in Figure 19 is accessed by
clicking the
Cal VCO
button on the main window.
A valid reference input signal must be present to complete VCO
calibration, and the VCO must be recalibrated any time the
VCO frequency changes by more than 40 MHz.
A VCO divider of 16 is suitable for all applications. However,
for applications where the phase detector frequency is <12 MHz,
using a smaller VCO calibration divider reduces calibration
time. Refer to the AD9522 data sheet for more details.
CHANNEL DIVIDER WINDOW
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Figure 20. AD9522 Channel Divider Window
The channel divider window shown in Figure 20 is accessed by
clicking the appropriate channel divider. It is usually sufficient
to change only the divide ratio because the evaluation software
and the AD9522 duty cycle correction feature ensures that the
output duty cycle remains very close to 50%.
You can also vary the phase offset by changing the
Phase Offset
Bits
setting. However, for the new phase to take effect, the SYNC
signal must be toggled via the
SYNC
button in the lower left
corner of the main window.
