SM843251-156
ClockWorks™
10-Gigabit Ethernet,
156.25MHz, Ultra-Low Jitter LVPECL Clock
Frequency Synthesizer
General Description
The SM843251-156 is a 10-Gigabit Ethernet, 156.25MHz
LVPECL clock frequency synthesizer and a member of the
ClockWorks™ family of devices from Micrel. It provides a
low-noise timing solution for high-speed, high-accuracy
synthesis of clock signals. It includes a patented
RotaryWave
®
architecture that provides a very stable clock
with very low noise.
Power supplies of either 2.5V or 3.3V are supported, with
superior jitter and phase noise performance. The device
synthesizes a 156.25MHz, low-noise, LVPECL output for
Ethernet applications. The crystal reference frequency is
25MHz.
The SM843251-156 is an excellent replacement for IDT
FemtoClocks®, with improved waveform integrity, and
jitter.
Data sheets and support documentation can be found on
Micrel’s web site at:
www.micrel.com.
Features
•
Generates a low-noise 156.25MHz LVPECL output
•
2.5V or 3.3V operating voltage
•
Typical phase jitter @156.25MHz~110fs
(1.875MHz
−
20MHz)
•
Crystal frequency: 25MHz
•
156.25MHz output frequency
•
Phase Noise @ 156.25MHz:
−
1kHz:
−123dBc/Hz
−
10kHz:
−130dBc/Hz
−
100kHz:
−135dBc/Hz
−
1MHz:
−140dBc/Hz
−
10MHz:
−161dBc/Hz
−
20MHz:
−166/dBc/Hz
•
Industrial temperature range
•
Green-, RoHS-, and PFOS-compliant
•
Available in 8-pin TSSOP
Applications
•
Gigabit Ethernet
•
10-Gigabit Ethernet
_______________________________________________________________________________________________________
Block Diagram
ClockWorks is a trademark of Micrel, Inc.
RotaryWave is a registered trademark of Multigig, Inc.
FemtoClocks is a registered trademark of IDT, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
408
) 944-0800 • fax + 1 (408) 474-1000 •
http://www.micrel.com
October 2010
M9999-100110-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM843251-156
Ordering Information
(1)
Part Number
SM843251-156KA
SM843251-156KA TR
Notes:
1.
2.
Devices are Green-, RoHS-, and PFOS-compliant.
Tape and Reel.
(2)
Package Type
K-8
K-8
Operating Range
Industrial
Industrial
Package Marking
843251-156
843251-156
Pin Configuration
8-Pin TSSOP (K-8)
Pin Description
Pin Number
1
2
3
4
5
6
7
8
Pin Name
V
DDA
V
EE
XTAL_OUT
XTAL_IN
NC
/Q0
Q0
V
DD
Type
PWR
PWR
O, (SE)
I, (SE)
−
O, (DIF)
O, (DIF)
PWR
LVPECL
LVPECL
12pF crystal
12pF crystal
Level
Pin Function
Analog 2.5V or 3.3V Power Supply. No filter resistor needed.
Ground.
Crystal Reference Output, no load caps needed.
Crystal Reference Input, no load caps needed.
No Connect
Differential Clock Output
Differential Clock Output
2.5V or 3.3V Power Supply
October 2010
2
M9999-100110-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM843251-156
Absolute Maximum Ratings
(1)
Supply Voltage (V
DDA
, V
DD
,) ........................................+4.6V
Input Voltage (V
IN
) ...............................−0.50V to V
DD
+ 0.5V
LVPECL Output Current (I
OUT
)
Continuous............................................................50mA
Surge ..................................................................100mA
Lead Temperature (soldering, 20sec.)....................... 260°C
Case Temperature ..................................................... 115°C
Storage Temperature (T
s
) .........................−65°C to +150°C
Operating Ratings
(2)
Supply Voltage (V
DD,
V
DDA
) ........................ +2.375 to +3.465
Ambient Temperature (T
A
) .......................... –40°C to +85°C
Junction Thermal Resistance
TSSOP (θ
JA
)(Still Air).......................................141°C/W
DC Electrical Characteristics
(3)
V
DD
= V
DDA
= 3.3V ±5%; T
A
= –40°C to +85°C, unless noted.
Symbol
V
DD
V
DDA
I
DDA
I
EE
Parameter
Core Supply Voltage
Analog Supply Voltage
Analog Supply Current
Total Supply Current
Included in I
EE
No load
Condition
Min.
3.135
3.135
Typ.
3.30
3.30
50
88
Max.
3.465
3.465
60
110
Units
V
V
mA
mA
V
DD
= V
DDA
= 2.5V ±5%; T
A
= –40°C to +85°C, unless noted.
Symbol
V
DD
V
DDA
I
DDA
I
EE
Parameter
Core Supply Voltage
Analog Supply Voltage
Analog Supply Current
Total Supply Current
Included in I
EE
No load
Condition
Min.
2.375
2.375
Typ.
2.50
2.50
50
80
Max.
2.625
2.625
60
100
Units
V
V
mA
mA
LVPECL DC Electrical Characteristics
(3, 4)
V
DD
= V
DDA
= 2.5V ±5% or 3.3V ±5%, T
A
= –40°C to +85°C, unless noted.
Symbol
V
OH
V
OL
V
SWING
Notes:
1.
Permanent device damage may occur if absolute maximum ratings are exceeded. This is a stress rating only and functional operation is not implied
at conditions other than those detailed in the operational sections of this data sheet. Exposure to absolute maximum rating conditions for extended
periods may affect device reliability.
The data sheet limits are not guaranteed if the device is operated beyond the operating ratings.
The circuit is designed to meet the DC specifications shown in the above table after thermal equilibrium has been established with a transverse
airflow greater than 500 lfpm.
See Figure 4 for load test circuit example.
Parameter
Output High Voltage
Output Low Voltage
Peak-to-Peak Output Voltage Swing
Condition
50Ω to V
DD
−
2V
50Ω to V
DD
−
2V
Min.
V
DD
– 1.145
V
DD
– 1.945
0.6
Typ.
V
DD
– 0.97
V
DD
– 1.77
0.8
Max.
V
DD
– 0.845
V
DD
– 1.645
1.0
Units
V
V
V
2.
3.
4.
October 2010
3
M9999-100110-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM843251-156
AC Electrical Characteristics
(5)
V
DD
= V
DDA
= 2.5V ±5% or 3.3V ±5%
, T
A
= –40°C to +85°C, unless noted.
Symbol
F
OUT
t
JITTER
t
R
/ t
F
O
DC
Note:
5.
The circuit is designed to meet the AC specifications shown in the above table(s) after thermal equilibrium has been established with a transverse
airflow greater than 500 lfpm.
Parameter
Output Frequency
RMS Phase Jitter (Output = 156.25 MHz)
Output Rise/Fall Time
Output Duty Cycle
Condition
25MHz Crystal
Integration Range: 1.875MHz to 20MHz
20% to 80%
Min.
Typ.
156.25
110
Max.
Units
MHz
fs
80
48
175
50
350
52
ps
%
Crystal Characteristics
Parameter
Mode of Oscillation
Frequency
Equivalent Series Resistance (ESR)
Shunt Capacitor, C0
Correlation Drive Level
Condition
12pF Load
Min.
Typ.
Max.
Units
MHz
Ω
pF
uW
Fundamental, Parallel Resonant
25
50
3
7
100
300
October 2010
4
M9999-100110-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM843251-156
Figure 1. Duty Cycle Timing
Figure 2. All Outputs Rise/Fall Time
Figure 3. RMS Phase Noise/Jitter
October 2010
5
M9999-100110-A
hbwhelp@micrel.com
or (408) 955-1690
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