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PDF XR81111 Data sheet ( Hoja de datos )
| Número de pieza | XR81111 | |
| Descripción | LVPECL Clock Synthesizer | |
| Fabricantes | Exar | |
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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
XR81111PHASENOISE(dBc/Hz)
2.5Vor3.3V
25MHz
Enable
FreqSelect
VCC
XTAL_IN
Q
100 MHzto156.25MHz
-40db
-60db
-80db
RMS Jitter = 532.3fs
Int Range 12KHz to 20MHz
XTAL_OUT Q
-100db
OE
FSEL1
FSEL0
VEE
-120db
-140db
-160db
-180db
100Hz
1KHz
10KHz
100 KHz
1MHz
10MHz
© 2014 Exar Corporation
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exar.com/XR81111
Rev 1B
1 page  
Pin Configuration
10
OE 1
9
8
Reserved
2
7
VEE 3
4
6
5
VCC
Q
Q
XR81111
Pin Assignments
Pin No.
Pin Name
1 OE
2 Reserved
3 VEE
4 XTAL_OUT
5 XTAL_IN
6Q
7Q
8 VCC
9 FSEL0
10 FSEL1
Type
Description
Input
(900K: pull-up)
Supply
Output enable pin - LVCMOS/LVTTL active high input. Outputs are enabled when OE = high.
Outputs are disabled when OE = low.
Reserved, leave this pin unconnected.
Negative supply pin.
Output
Input
Output
Output
Supply
Crystal oscillator output.
Crystal oscillator input.
Positive LVPECL output.
Inverted LVPECL output.
Power supply pin.
Input
Output frequency select pin, LSB (LVCMOS/LVTTL input).
(900K: pull-dwn)
Input
Output frequency select pin, MSB (LVCMOS/LVTTL input).
(900K: pull-dwn)
© 2014 Exar Corporation
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exar.com/XR81111
Rev 1B
5 Page 
Mechanical Dimensions
10-Pin QFN
XR81111
© 2014 Exar Corporation
11 / 12
exar.com/XR81111
Rev 1B
11 Page | ||
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| PDF Descargar | [ Datasheet XR81111.PDF ] | |
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