Clock Synchronizer/Adapter for
Communications
September 2006
XRT8000
FEATURES
D
Clock Adaptation for Most Popular
Telecommunication Frequencies
D
Wide Input Frequency Range
D
Programmable Output Frequencies
D
Less than 0.05UI Wide Band Output Jitter
D
Low Power Operation (5V and 3.3V)
D
Maximum Lock Time of 45mS
GENERAL DESCRIPTION
The XRT8000 is a dual phase-locked loop chip that
generates two simultaneous, very low jitter, output clocks
for synchronization applications in wide area networking
systems. The outputs are phase locked to the input
signal. The chip has four basic modes of operation;
referred to as master (FORWARD, REVERSE) and slave
(FORWARD, REVERSE) modes (See Figure 1). In the
FORWARD mode it accepts up to 16th harmonic of either
1.544MHz or 2.048MHz as input reference and generates
1.2kHz and multiples of 2.4kHz, 56kHz or 64kHz. In the
REVERSE mode an input clock of 56kHz or 64kHz is used
ORDERING INFORMATION
Part No.
XRT8000IP
XRT8000ID
Package
18 Lead 300 Mil PDIP
18 Lead 300 Mil JEDEC SOIC
Operating Temperature
Range
-40°C to +85°C
-40°C to +85°C
D
Cascadable
D
No External Components Needed
D
Lock Detect Indication Pin
APPLICATIONS
D
DSU’s, CSU’s and Access Equipment
D
ISDN Terminals
D
Concentrators and Multiplexers
to generate 1.544MHz or 2.048MHz output clocks. The
SLAVE (FORWARD, REVERSE) modes generate the
same output frequencies as the MASTER (FORWARD/
REVERSE MODES) except that the input frequency (F
IN
)
is 8kHz. An optional divide by eight can be enabled at
each of the outputs.
The input and output frequency selection can be done
through a serial microprocessor interface. The XRT8000
is available in either 18 pin SOIC package or 18 pin plastic
DIP.
XRT8000
CLK2
n x 1.544{T1}
n x 2.048{E1}
1 <= n <= 16
F
IN
CLK1
K x 56kHz
K x 64kHz
1.2kHz
2.4 x K
to
43.2kHz
SYNC 8kHz
1 <= K <= 32
56kHz
64kHz
XRT8000
CLK2
F
IN
CLK1
XRT8000
B
T1 (1.544)
or
E1 (2.048)
SYNC
8kHz
CLK2
F
IN
CLK1
A
1 <= K <= 18
A/ B
SYNC
MASTER FORWARD
MASTER REVERSE
SLAVE
FORWARD/REVERSE
Figure 1. System Diagram
Rev.1.11
E1999--2006
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 z (510) 668-7000 z FAX (510) 668-7017 z www.exar.com
EXAR [ EXAR CORPORATION ]
