Datasheet

Evaluation Board User Guide UG-076
Rev. 0 | Page 5 of 16
QUICK START GUIDE TO THE AD9520 PLL
When the evaluation software is installed, the evaluation board
is connected, and the software is loaded, use the following steps
to configure and lock the PLL. These steps assume that the input
signal is present, the evaluation board has not been modified,
and that the PLL loop filter is suitable for the user’s application.
This quick start guide covers only simple PLL operation to start
the PLL. See the AD9520 data sheet and Evaluation Software
Components section for a detailed explanation of the various
AD9520 features.
The following case is an example for the AD9520-4 using the
values in Table 1.
Table 1.
Parameter Value
Input Frequency 19.44 MHz on REF1
Output Frequency 148.5 MHz
Reference Divider 72
Phase Detector Frequency 270 kHz
Feedback Divider 5500
VCO Frequency 1485 MHz
VCO Divider 2
Channel Divider 5
1. Turn the PLL on by selecting Normal Op from the PLL
MODE box found at the top of the main window (see
Figure 8).
2. Enter the intended reference input frequency (in
megahertz) in the REF 1 (MHz) box at the upper left
corner of the main window.
3. Click the triangular buffer symbol immediately to the
right of the input reference frequency (see Figure 4) text
boxes to load the Reference Input Control window shown
in Figure 5. Turn the REF1 reference input buffer on by
selecting the Enable REF 1 check box, and then click OK.
08746-024
Figure 4. Buffer Symbol
08746-004
Figure 5. Reference Input Control Window
4. When the window closes, the WRITE button under the
REGISTER W/R section in Figure 8 blinks red. This
indicates that there are settings that have not been loaded
to the AD9520 evaluation board. Click the blinking red
WRITE button to load these settings to the evaluation
board.
5. Select the VCO as the input to the clock distribution
circuitry by clicking the mux symbol that is located
immediately to the right of the VCO (MHz) box (see
Figure 6).
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Figure 6. Buffer Symbol
When the VCO is selected, the border of the VCO (MHz)
box changes from gray to black. The current VCO
frequency is shown in the VCO (MHz) box.