XR81111 Datasheet, PDF (1/12 Pages) Exar Corporation – Universal Clock - High Frequency LVPECL Clock Synthesizer

XR81111
Universal Clock - High Frequency
LVPECL Clock Synthesizer
General Description
The XR81111-CA04 is a clock synthesizer with Integer divider, LVPECL
driver, 3.3V/2.5V supply, taking a 25MHz Xtal input and providing one of four
selectable output frequencies. The device is optimized for use with a 25MHz
crystal (or system clock) and generates a selection of output frequencies -
156.25MHz for 10GE/XAUI, 150MHz for SAS, 125MHz for GE and 100MHz
for PCIe applications.
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
12KHz to 20MHz range that is widely used in WAN systems. Most LAN
applications however use the integration range of 1.875MHz to 20MHz.
These clock devices show a very good high frequency noise floor below -
150dB.
The XR81111 is a family of Universal Clock synthesizer devices in QFN-10
packages that are footprint compatible with industry standard 5mm x 7mm
oscillators. The devices generate ANY frequency in the range of 100 MHz to
1.5GHz by utilizing a highly flexible delta sigma modulator and a wide rang-
ing VCO. The high clock frequency LVPECL outputs have very low phase
noise jitter of sub 0.6ps, while consuming extremely low power. These
devices can be used with standard crystals or external system clock and can
be configured to select from four different frequency multiplier settings to
support a wide variety of applications. This family of products have an
extremely low power PLL block with core power consumption less than 40%
of the equivalent devices from competition. By second sourcing several of
the existing sockets, these devices provides a very compelling power effi-
ciency value benefit across all market segments.
FEATURES
• XR81111-CA04: Factory Configured
• Footprint compatible with 5mm x 7mm differen-
tial oscillators
• One differential LVPECL output pair
• Crystal oscillator interface which can also be
overdriven using a single-ended reference clock
• Output frequency range: 100MHz - 156.25MHz
• Crystal/input frequency: 25MHz, parallel resonant
crystal
• VCO range: 2GHz - 3GHz
• RMS phase jitter @ 156.25MHz, 12kHz - 20MHz:
<0.60ps
• Full 3.3V or 2.5V operating supply
• -40°C to 85°C ambient operating temperature
• Lead-free (RoHS 6) package
APPLICATIONS
• 10GE, GE LAN/WAN
• 2.5G/10G SONET/SDH/OTN
• xDSL, PCIe
• Low-jitter Clock Generation
• Synchronized clock systems
Ordering Information – page 12
Other clock multiplier and/or driver configurations are possible in this clock
family and can be requested from the factory
Typical Application
XR 81111ͲCA 04
2.5Vor3.3V
V_CC
Q
25MHz
Enable
FreqSelect
XTAL_IN
XTAL_OUT ^Q
OE
FSEL1
FSEL0
V_EE
100 MHzto156.25MHz
-40db
-60db
-80db
-100db
-120db
-140db
-160db
-180db
100Hz
XR81111PHASENOISE(dBc/Hz)
RMS Jitter = 532.3fs
Int Range 12KHz to 20MHz
1KHz
10KHz
100 KHz
1MHz
10MHz
© 2014 Exar Corporation
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exar.com/XR81111
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