© 2014 Exar Corporation
XR81101
Universal Clock - High Frequency
LVCMOS Clock Synthesizer
exar.comXR81101
Rev 1A
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General Description
The XR81101-AA02 is a clock synthesizer operating at a 3.3V/2.5V sup-
ply with Integer divider, using a 25MHz parallel resonant crystal reference
input provides a 125MHz LVCMOS output. The device is optimized for
use with a 25MHz crystal (or system clock) and generates a 125MHz out-
put clock for GE applications. The LVCMOS output has very low phase
noise jitter of sub 150fs, while consuming extremely low power.
The application diagram below shows a typical synthesizer configuration
with any standard crystal oscillating in fundamental mode. Internal load
capacitors are optionally available to minimize/eliminate external crystal
loads. A system clock can also be used to overdrive the oscillator for a
synchronous timing system.
The typical phase noise plot below shows the jitter integrated over the
1.875MHz to 20MHz range that is widely used in WAN systems. These
clock devices show a very good high frequency noise floor below -150dB.
The XR81101 is a family of Universal Clock synthesizer devices in
TSSOP-8 packages. The devices generate ANY frequency in the range of
10MHz to 200MHz by utilizing a highly flexible delta sigma modulator and
a wide ranging VCO. These devices can be used with standard crystals or
external system clock to support a wide variety of applications. This family
of products has an extremely low power PLL block with core power con-
sumption 40% less than the equivalent devices from competition. By sec-
ond sourcing several of the existing sockets, these devices provides a
very compelling power efficiency value benefit across all market seg-
ments.
Other clock multiplier and/or driver configurations are possible in this
clock family and can be requested from the factory
FEATURES
• XR81101-AA02: Factory configured
• One LVCMOS output
• Crystal oscillator interface which can also be
overdriven using a single-ended reference clock
• Output frequency: 125MHz
• Crystal/input frequency: 25MHz, parallel resonant
crystal
• RMS phase jitter @ 125MHz, 1.875MHz - 20MHz:
< 150fs
• Full 3.3V or 2.5V operating supply
• -40°C to 85°C ambient operating temperature
• Lead-free (RoHS 6) package
APPLICATIONS
• Gigabit Ethernet
• Low-jitter Clock Generation
• Synchronized clock systems
Ordering Information – page 8
Typical Application
