Analog Devices AD9520-0, Руководство пользователя

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Evaluation Board User Guide UG-076
Rev. A | Page 11 of 16
CHARGE PUMP SETUP WINDOW
The Charge Pump Setup window shown in Figure 17 is
accessed by clicking the
CHARGE PUMP
box in the main
window.
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Figure 17. Charge Pump Setup 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 useful for debugging the PLL and
isolating the output driver section of the AD9520 from the PLL
section.
ZERO DELAY WINDOW
The Zero Delay window shown in Figure 18 is accessed by
clicking the ZERO DELAY box in the main window.
When internal zero delay mode is selected, the window shrinks
because only Divider 0 can operate in the internal zero delay mode.
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46
-014
Figure 18. Zero Delay Window
VCO CALIBRATION WINDOW
The Calibrate VCO window shown in Figure 19 is accessed by
clicking the Cal VCO button in the main window.
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Figure 19. Calibrate VCO 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
AD9520 data sheet for more details.
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
AD9520 duty cycle correction feature ensure that the
output duty cycle remains very close to 50%.
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Figure 20. Channel Divider Window
The user 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.