a
155.52 MHz Frequency Synthesizer
AD809
FEATURES
155.52 Mbps ports. The AD809 can be applied to create the trans-
mit bit clock for one or more ports.
Frequency Synthesis to 155.52 MHz
19.44 MHz or 9.72 MHz Input
Reference Signal Select Mux
Single Supply Operation: +5 V or –5.2 V
Output Jitter: 2.0 Degrees RMS
Low Power: 90 mW
10 KH ECL/PECL Compatible Output
10 KH ECL/PECL/TTL/CMOS Compatible Input
Package: 16-Pin Narrow 150 Mil SOIC
An input signal multiplexer supports loop-timed applications
where a 155.52 MHz transmit bit clock is recovered from the
155.52 Mbps received data.
The low jitter VCO, low power and wide operating temperature
range make the device suitable for generating a 155.52 MHz bit
clock for SONET/SDH/Fiber in the Loop systems.
The device has a low cost, on-chip VCO that locks to either
8× or 16× the frequency at the 19.44 MHz or 9.72 MHz input.
No external components are needed for frequency synthesis; how-
ever, the user can adjust loop dynamics through selection of a
damping factor capacitor whose value determines loop damping.
PRODUCT DESCRIPTION
The AD809 design guarantees that the clock output frequency
will drift low (by roughly 20%) in the absence of a signal at the
input.
The AD809 provides a 155.52 MHz ECL/PECL output clock from
either a 19.44 MHz or a 9.72 MHz TTL/CMOS/ECL/PECL refer-
ence frequency. The AD809 functionality supports a distributed
timing architecture, allowing a backplane or PCB 19.44 MHz or
9.72 MHz timing reference signal to be distributed to multiple
The AD809 consumes 90 mW and operates from a single power
supply at either +5 V or –5.2 V.
FUNCTIONAL BLOCK DIAGRAM
CF1 CF2
8
7
CLKIN
13
12
(19.44MHz
OR
9.72MHz)
LOOP
FILTER
AUTO
SELECT
PFD
VCO
CLKINN
BW
ADJUST
10
2
TTL/CMOSIN
AUTO SELECT
DIVIDE BY 8/16
AD809
5
4
CLKOUT
PECLIN
MUX
(155MHz)
CLKOUTN
(155MHz
PECL
1
PECLINN
15
MUX
OUTPUT)
REV. A
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reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
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© Analog Devices, Inc., 1997