Pll Reference Input Window; Pll Configuration Window (Config Pll) - Analog Devices AD9522 Series User Manual

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The AD9522 evaluation software is composed of subsections
that correspond to the AD9522's major functional blocks. These
subsections are listed in the following sections, and each of
these has its own window. From the main window, each
functional block can be accessed by clicking that block in the
main window.
When a subwindow closes after clicking OK, the WRITE box
on the main window (under the REGISTER W/R control
section) may blink red. This indicates that there are settings that
have not been loaded to the AD9522 evaluation board. Clicking
the blinking red WRITE box loads these settings to the
evaluation board.

PLL REFERENCE INPUT WINDOW

Figure 9. AD9522 Reference Input Control Window
The reference input control window is shown in Figure 9,
and is accessed by clicking either of the triangular buffer symbols
immediately to the right of the REF 1 (MHz) and REF 2 (MHz)
input reference frequency boxes (see Figure 10).
Figure 10. Buffer Symbol
This window is used to enable the PLL reference inputs, which
are powered down by default.
Select Enable REF 1, or Enable REF 2, or both to enable the
appropriate reference input, and click OK when finished. If a
differential input is used, select the Use Differential Ref Mode
(Unchecked = Single-Ended Mode) check box. Note that this
mode should not be used simultaneously with Enable REF 1 or
Enable REF 2.
If Disable Switchover De-Glitch is activated, the AD9522
maintains the phase relationship between the active input and
PLL output during a reference switchover. Otherwise, the
AD9522 minimizes the phase disturbance at the output during
a reference switchover.
Enable XTAL Oscillator should be selected if you intend to
connect a crystal to the reference input.
Enable PLL CMOS Ref Input DC Offset forces the dc bias
point of the single-ended reference input to be different from
the switching point, and is useful for preventing an ac-coupled
input from chattering when the reference input is lost.

PLL CONFIGURATION WINDOW (CONFIG PLL)

Figure 11. AD9522 PLL Configuration Window
The PLL configuration window shown in Figure 11 has three
sections. This window is opened by clicking the Config PLL
button on the main window.
The SyncB Counter Reset Mode section indicates whether the
R, A, and B counters are reset when the SYNC pin is activated,
and controls 0x019[7:6]. See the AD9522 data sheet for more
details.
The PLL Status Registers section allows you to see the current
value of the read-only PLL status register, Address 0x01F. This
function is very useful for ensuring that the AD9522 VCO has
finished VCO calibration and that the PLL is locked.
The Settings section controls the various PLL settings such
as holdover. The AD9522 data sheet describes these functions
in detail.
Rev. 0 | Page 8 of 16
Evaluation Board User Guide