XR81102
Universal Clock - High Frequency
LVPECL Clock Synthesizer
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
XR81102 PHASE NOISE (dBc/Hz)
-40db
XR81102 CA02
2.5V or 3.3V
V
CC
XTAL_IN
25MHz
XTAL_OUT
Enable
OE
V
EE
-160db
-180db
100Hz
Q
125MHz
Q
-60db
-80db
-100db
-120db
-140db
RMS Jitter =
120.9fs
Int Range 1.875MHz to 20MHz
1KHz
10KHz
100 KHz
1MHz
10MHz
© 2014 Exar Corporation
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Rev 1B
XR81102
Absolute Maximum Ratings
Stresses beyond those listed under Absolute Maximum
Ratings may cause permanent damage to the device.
Exposure to any Maximum Rating condition for extended
periods may affect device reliability and lifetime.
Supply Voltage..........................................................+4.2V
Input Voltage......................................-0.5V to VCC + 0.5V
Output Voltage...................................-0.5V to VCC + 0.5V
Reference Frequency/Input Crystal.........10MHz to 60MHz
Storage Temperature................................-55°C to +125°C
Lead Temperature (Soldering, 10 sec).....................300°C
ESD Rating (HBM - Human Body Model)....................2kV
Operating Conditions
Operating Temperature Range.....................-40°C to +85°C
© 2014 Exar Corporation
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XR81102
Electrical Characteristics
Unless otherwise noted: T
A
= -40°C to +85°C, V
CC
= 3.3V±5% or 2.5V±5%, V
EE
= 0V
Symbol
Parameter
Conditions
*
Min
Typ
Max
Units
3.3V Power Supply DC Characteristics
V
CC
I
EE
Power Supply Voltage
Power Supply Current
Measured at 156.25MHz and includes
the output load current
•
3.135
3.3
68
3.465
V
mA
2.5V Power Supply DC Characteristics
V
CC
I
EE
Power Supply Voltage
Power Supply Current
Measured at 156.25MHz and includes
the output load current
•
2.375
2.5
58
2.625
V
mA
LVCMOS/LVTTL DC Characteristics
V
IH
Input High Voltage
V
CC
= 3.465V
V
CC
= 2.625V
V
IL
Input Low Voltage
V
CC
= 3.465V
V
CC
= 2.625V
I
IH
I
IL
Input High Current (OE, FSEL[1:0])
Input Low Current (OE, FSEL[1:0])
V
IN
= V
CC
= 3.465V or 2.625V
V
IN
= 0V, V
CC
= 3.465V or 2.625V
•
•
•
•
•
•
-10
2.42
1.83
-0.3
-0.3
V
CC
+ 0.3
V
CC
+ 0.3
1.03
0.785
15
V
V
V
V
µA
µA
LVPECL DC Characteristics
V
OH
V
OL
V
SWING
Output High Voltage
Output Low Voltage
Peak-to-Peak Output Voltage Swing
•
•
•
V
CC
- 1.3
V
CC
- 2.0
0.6
V
CC
- 0.4
V
CC
- 1.6
1.2
V
V
V
Crystal Characteristics
X
Mode
X
f
ESR
C
S
Mode of Oscillations
Frequency
Equivalent Series Resistance
Shunt Capacitance
Fundamental
25
50
7
MHz
Ω
pF
AC Characteristics
f
OUT
t
jit
( )
t
jit
(cc)
t
R
/t
F
Odc
Output Frequency
RMS Phase Jitter
125MHz
Integration Range 1.875MHz-20MHz
Using 25MHz, 18pF resonant crystal
20% to 80%
•
•
•
100
48
125
0.15
MHz
pS
Cycle-to-Cycle Jitter
Output Rise/Fall Time
Output Duty Cycle
10
500
52
pS
pS
%
* Limits applying over the full operating temperature range are denoted by a “•”.
© 2014 Exar Corporation
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exar.com/XR81102
Rev 1B
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