XR81101
Universal Clock - High Frequency
LVCMOS Clock Synthesizer
General Description
FEATURES
The XR81101-AA02 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 LVCMOS output. The device is optimized for
use with a 25MHz crystal (or system clock) and generates a 125MHz output clock for GE applications. The LVCMOS output has very low phase
noise jitter of sub 150fs, while consuming extremely low power.
• 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
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.
APPLICATIONS
• Gigabit Ethernet
• Low-jitter Clock Generation
• Synchronized clock systems
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 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.
Ordering Information – page 8
Other clock multiplier and/or driver configurations are possible in this
clock family and can be requested from the factory
Typical Application
XR81101 ͲAA02
2.5Vor3.3V
XR81101PHASENOISE(dBc/Hz)
-40db
VCC
XTAL_IN
Q
-60db
125MHz
-80db
RMS Jitter = 123.6fs
Int Range 1.875MHz to 20MHz
25MHz
-100db
XTAL_OUT
-120db
Enable
OE
VEE
-140db
-160db
-180db
100Hz
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1KHz
10KHz
100 KHz
1MHz
10MHz
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Absolute Maximum Ratings
Operating Conditions
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.
Operating Temperature Range.....................-40°C to +85°C
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
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Electrical Characteristics
Unless otherwise noted: TA = -40°C to +85°C, VCC = 3.3V±5% or 2.5V±5%, VEE = 0V
Symbol
Parameter
Conditions
*
Min
Typ
Max
Units
•
3.135
3.3
3.465
V
3.3V Power Supply DC Characteristics
VCC
Power Supply Voltage
IEE
Power Supply Current
125MHz with output unloaded.
24
mA
2.5V Power Supply DC Characteristics
VCC
Power Supply Voltage
IEE
Power Supply Current
•
2.375
125MHz with the output unloaded.
2.5
2.625
21
V
mA
LVCMOS/LVTTL DC Characteristics
Symbol
VIH
VIL
Parameter
Input High Voltage
Input Low Voltage
Conditions
*
Min
VCC = 3.465V
•
VCC = 2.625V
Typ
Max
Units
2.42
VCC + 0.3
V
•
1.83
VCC + 0.3
V
VCC = 3.465V
•
-0.3
1.03
V
VCC = 2.625V
•
-0.3
0.785
V
15
µA
IIH
Input High Current (OE, FSEL[1:0])
VIN = VCC = 3.465V or 2.625V
•
IIL
Input Low Current (OE, FSEL[1:0])
VIN = 0V, VCC = 3.465V or 2.625V
•
-10
µA
0.8 x VCC
V
LVCMOS DC Characteristics
VOH
Output High Voltage
Output unloaded
•
VOL
Output Low Voltage
Output unloaded
•
0.1 x VCC
V
Crystal Characteristics
XMode
Mode of Oscillations
Fundamental
Xf
Frequency
ESR
Equivalent Series Resistance
50
Ω
CS
Shunt Capacitance
7
pF
25
MHz
AC Characteristics
fOUT
Output Frequency
tjit(I)
RMS Phase Jitter
125MHz (Int. Range 1.875MHz-20MHz)
tjit(cc)
Cycle-to-Cycle Jitter
Using 25MHz, 18pF resonant crystal
•
tR/tF
Output Rise/Fall Time
20% to 80%
•
Odc
Output Duty Cycle
•
125
MHz
0.15
pS
10
pS
100
550
pS
48
52
%
* Limits applying over the full operating temperature range are denoted by a “•”.
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Pin Configuration
VCC
1
8
VCC
OE
2
7
Q
XTAL_out
3
6
VEE
XTAL_in
4
5
nc
Pin Assignments
Pin No.
Pin Name
Type
Description
1
VCC
Supply
2
OE
Input
(900K: pull-up)
3
XTAL_OUT
4
XTAL_IN
5
nc
6
VEE
Supply
Negative supply pin.
7
Q
Output
LVCMOS output.
8
VCC
Supply
Power supply pin.
© 2014 Exar Corporation
Output
Input
No Connect
Power supply pin.
Output enable pin - LVCMOS/LVTTL active high input. Outputs are enabled when OE = high.
Outputs are disabled when OE = low.
Crystal oscillator output.
Crystal oscillator input.
Unused, do not connect.
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Functional Block Diagram
OE
XTAL_IN
OSC
VCO
PDF & LPF
Divide
by N
Q
XTAL_OUT
Divide
by M
M/N = 5
Typical Performance Characteristics
Figure 1 shows a typical phase noise performance plots for a 125MHz clock output. The data was taken using the industry
standard Agilent E5052B phase noise instrument. The integration range is 1.875MHz to 20MHz.
Figure 1: 125MHz Operation, Typical Phase Noise at 3.3V
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Application Information
Output Signal Timing Definitions
Termination for LVCMOS Outputs
The following diagrams clarify the common definitions of
the AC timing measurements.
The termination schemes shown in Figure 2 and Figure 3
are typical for LVCMOS outputs. A split supply approach
can be used utilizing the scope’s internal 50: impedance,
as shown in Figure 4.
80%
80%
LVCMOS
Output
20%
20%
3.3V ± 5%
3.3V ± 5%
100:
tF
tR
Z = 50:
LVCMOS
Output
100 :
High Impedance
scope probe
Figure 5: Cycle-to-Cycle Jitter
LVCMOS
Output
Figure 2: XR81101 3.3V LVCMOS Output Termination
VCC/2
t PW
t Period
2.5V ± 5%
2.5V ± 5%
Odc =
t PW
t Period
100%
100:
Z = 50:
LVCMOS
Output
Figure 6: Output Rise/Fall Time
:
High Impedance
scope probe
Figure 3: XR81101 2.5V LVCMOS Output Termination
+Vcc/2 ± 5%
Vcc
LVCMOS
Output
Vss
Z = 50:
:
-Vcc/2 ± 5%
Scope
Figure 4: XR81101 Split Supply LVCMOS Output Termination
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Mechanical Dimensions
8-Pin TSSOP
T
T
T
T
Note: The side, top and landing pattern drawings are general to TSSOP packaging but the table is specific to the 8pin TSSOP.
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Ordering Information
Part Number
Package
Green
Operating Temperature
Range
Shipping Packaging
Marking
XR81101-AA02-F
8-pin TSSOP
Yes
-40°C to +85°C
Tube
T01
XR81101-AA02TR-F
8-pin TSSOP
Yes
-40°C to +85°C
Tape & Reel
T01
Eval Board
N/A
N/A
N/A
XR81101EVB
N/A
Revision History
Revision
Date
1A
April 2014
Description
Initial release. [ECN1416-07 l 04/18/2014]
For Further Assistance:
Email: commtechsupport@exar.com
Exar Technical Documentation: http://www.exar.com/techdoc/
Exar Corporation Headquarters and Sales Offices
48720 Kato Road
Tel: +1 (510) 668-7000
Fremont, CA 95438 - USA
Fax: +1 (510) 668-7001
NOTICE
EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation
assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free
of patent infringement. Charts and schedules contained herein are only for illustration purposes and may vary depending upon a user’s specific application. While the information
in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies.
EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to
cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation
receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances.
Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
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