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APPLICATION NOTE
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The AD9552: A Programmable Crystal Oscillator for Network Clocking Applications
by Ken Gentile
The ubiquitous quartz crystal oscillator has been the workhorse
of timekeeping applications for decades. Low cost, coupled with
relatively high stability, is the driving force behind the success of
the quartz crystal oscillator in a broad range of applications.
The high resonant Q factor makes the quartz crystal oscillator
an attractive candidate for the resonant element in fixed fre-
quency oscillators. However, an ever-increasing number of
network clock applications require a stable, single frequency
oscillator as a source for synthesizing different network
frequencies. The AD9552 is a low cost, integrated solution
for such applications.
Rev. 0 | Page 1 of 8
PHASE
DETECTOR
LOOP
FILTER
VOLTAGE
CONTROLLED
OSCILLATOR
FEEDBACK
DIVIDER
(N)
OSCILLATOR
f
REF
f
OUT
= N ×
f
REF
QUARTZ
CRYSTAL
PLL
07918-001
Figure 1. PLL-Based Frequency Upconverter
