© 2014 Exar Corporation
XR81102
Universal Clock - High Frequency
LVPECL Clock Synthesizer
exar.com/XR81102
Rev 1B
1 / 8
General Description
The XR81101-CA02 is a clock synthesizer operating at a 3.3V/2.5V supply
with Integer divider, using a 25MHz parallel resonant crystal reference input
provides a 125MHz LVPECL outputs. The device is optimized for use with a
25MHz crystal (or system clock) and generates a 125MHz output clock for
GE applications. The LVPECL outputs have 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 syn-
chronous 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 XR81102 is a family of Universal Clock synthesizer devices in TSSOP-
8 packages. The devices generate ANY frequency in the range of 100MHz
to 1.5GHz 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 prod-
ucts has an extremely low power PLL block with core power consumption
40% less than the equivalent devices from competition. By second sourcing
several of the existing sockets, these devices provides a very compelling
power efficiency value benefit across all market segments.
Other clock multiplier and/or driver configurations are possible in this clock
family and can be requested from the factory
FEATURES
• XR81102-CA02: Factory configured
• One differential LVPECL output pair
• 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
