SM802108
ClockWorks™ 10GbE & GbE (156.25MHz,
125MHz) Ultra-Low Jitter, LVPECL
Frequency Synthesizer
General Description
The SM802108 is a member of the ClockWorks™ family of
devices from Micrel and provides an extremely low-noise
timing solution for GbE and 10GbE Ethernet clock signals.
It is based upon a unique patented RotaryWave
®
architecture that provides very low phase noise.
The device operates from a 3.3V or 2.5V power supply
and synthesizes two LVPECL output clocks at 156.25MHz
and another two at 125MHz. The SM802108 accepts a 25
MHz crystal or LVCMOS reference clock.
Data sheets and support documentation can be found on
Micrel’s web site at:
www.micrel.com.
Features
•
Generates two LVPECL clock outputs at 156.25MHz
and two LVPECL clock outputs at 125MHz
•
2.5V or 3.3V operating range
•
Typical phase jitter @ 156.25MHz
(1.875MHz to 20MHz): 110fs (typical) at 3.3V
•
Industrial temperature range
•
Green, RoHS, and PFOS compliant
•
Available in 24-pin 4mm
×
4mm QFN package
Applications
•
10Gigabit Ethernet
•
Gigabit Ethernet
___________________________________________________________________________________________________________
Block Diagram
ClockWorks is a trademark of Micrel, Inc
RotaryWave is a registered trademark of Multigig, 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
January 2011
M9999-012111-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM802108
Ordering Information
Part Number
SM802108UMG
SM802108UMGR
Note:
1. Devices are Green, RoHS, and PFOS compliant.
Marking
802108
802108
Shipping
Tube
Tape and Reel
Junction Temperature Range
–40°C to +85°C
–40°C to +85°C
Package
24-Pin QFN
24-Pin QFN
Pin Configuration
24-Pin QFN
(Top View)
Pin Description
Pin Number
16, 17
20, 21
23, 24
3, 4
1
2
Pin Name
/Q0, Q0
/Q1, Q1
/Q2, Q2
/Q3, Q3
VDDO2
VSSO2
Pin Type
O, (DIF)
O, (DIF)
PWR
PWR
Pin Level
LVPECL
LVPECL
Pin Function
Differential Clock Outputs from Bank 1
156.25MHz
Differential Clock Outputs from Bank 2
125MHz
Power Supply for Output Bank 2
Power Supply Ground for Output Bank 2
PLL Bypass, Selects Output Source
5
PLL_BYPASS
I, (SE)
LVCMOS
0 = Normal PLL Operation
1 = Output from Input Reference Clock or Crystal
45KΩ pull-down
6
XTAL_SEL
I, (SE)
LVCMOS
Selects PLL Input Reference Source
0 = REF_IN, 1 = XTAL, 45KΩ pull-up
January 2011
2
M9999-012111-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM802108
Pin Description (Continued)
Pin Number
7, 12, 15, 19
8
9
10
11
13, 14
18
22
Pin Name
TEST
VDD
REF_IN
XIN
XOUT
VSS
VDDO1
VSSO1
PWR
I, (SE)
I, (SE)
O, (SE)
PWR
PWR
PWR
LVCMOS
12pF crystal
12pF crystal
Pin Type
Pin Level
Pin Function
Factory Test Pins, Do not connect anything to these pins.
Core Power Supply
Reference Clock Input
Crystal Reference Input, no load caps needed.
See Fig. 5.
Crystal Reference Output, no load caps needed.
See Fig. 5.
Core Power Supply Ground
Power Supply for Output Bank 1
Power Supply Ground for Output Bank 1
Application Information
Input Reference
When operating with a crystal input reference, do not
apply a switching signal to REF_IN.
Crystal Layout
Keep the layers under the crystal as open as possible.
Do not place switching signals or noisy supplies under
the crystal.
Truth Table
PLL_BYPASS
0
1
−
−
XTAL_SEL
−
−
0
1
INPUT
−
−
REF_IN
XTAL
OUTPUT
PLL
XTAL/REF_IN
−
−
January 2011
3
M9999-012111-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM802108
Absolute Maximum Ratings
(1)
Supply Voltage (V
DD
, V
DDOx
) ........................................+4.6V
Input Voltage (V
IN
). ............................. –0.50V to V
DD
+ 0.5V
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
DDOx
) ................. +2.375V to +3.465V
Ambient Temperature (T
A
) .......................... –40°C to +85°C
Junction Thermal Resistance
(3)
QFN (θ
JA
)
Still-Air.........................................................50°C/W
QFN (ψ
JB
)
Junction-to-Board .......................................30°C/W
DC Electrical Characteristics
(4)
V
DD
= V
DDO1/2
= 3.3V
±5%
or 2.5V
±5%
V
DD
= 3.3V
±5%,
V
DDO1/2
= 3.3V
±5%
or 2.5V
±5%
T
A
=
−40°C
to
+85°C.
Symbol
V
DD
, V
DDOx
V
DD
, V
DDOx
I
DD
I
DD
Parameter
2.5V Operating Voltage
3.3V Operating Voltage
Supply current V
DD
+ V
DDO
Supply current V
DD
+ V
DDO
Outputs open; REF_IN source,
XTAL_SEL = 0
Outputs open; CRYSTAL source,
XTAL_SEL = 1
Condition
Min.
2.375
3.135
Typ.
2.5
3.3
130
145
Max.
2.625
3.465
165
185
Units
V
V
mA
mA
LVPECL DC Electrical Characteristics
(4)
V
DD
= V
DDO1/2
= 3.3V
±5%
or 2.5V
±5%
V
DD
= 3.3V
±5%,
V
DDO1/2
= 3.3V
±5%
or 2.5V
±5%
T
A
=
−40°C
to
+85°C.
R
L
= 50Ω to V
DDO
−
2V
Symbol
V
OH
V
OL
V
SWING
Note:
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.
Package thermal resistance assumes exposed pad is soldered (or equivalent) to the devices most negative potential on the PCB.
The circuit is designed to meet the AC and DC specifications shown in the above table(s) after thermal equilibrium has been established.
Parameter
Output High Voltage
Output Low Voltage
Output Voltage Swing
Condition
Min.
V
DDO
– 1.145
V
DDO
– 1.945
0.6
Typ.
V
DDO
– 0.97
V
DDO
– 1.77
0.8
Max.
V
DDO
– 0.845
V
DDO
– 1.645
1.0
Units
V
V
V
2.
3.
4.
January 2011
4
M9999-012111-A
hbwhelp@micrel.com
or (408) 955-1690
Micrel, Inc.
SM802108
LVCMOS (PLL_BYPASS, XTAL_SEL) DC Electrical Characteristics
(4)
V
DD
= 3.3V
±5%,
or 2.5V
±5%,
T
A
=
−40°C
to
+85°C.
Symbol
V
IH
V
IN
I
IH
I
IL
Parameter
Input High Voltage
Input Low Voltage
Input High Current
Input Low Current
V
DD
= V
IN
= 3.465V
V
DD
= 3.465V, V
IN
= 0V
−5
Condition
Min.
2
−0.3
Typ.
Max.
V
DD
+ 0.3
0.8
150
Units
V
V
μA
μA
REF_IN DC Electrical Characteristics
(4)
V
DD
= 3.3V
±5%,
or 2.5V
±5%,
T
A
=
−40°C
to
+85°C.
Symbol
V
IH
V
IL
I
IN
I
IN
Parameter
Input High Voltage
Input Low Voltage
Input Current
Input Current
XTAL_SEL = V
IL
, V
IN
= 0V to V
DD
XTAL_SEL = V
IH
, V
IN
= V
DD
Condition
Min.
1.1
−0.3
−5
20
Typ.
Max.
V
DD
+ 0.3
0.6
5
Units
V
V
μA
µA
Crystal Characteristics
NDK NX2520SA
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
January 2011
5
M9999-012111-A
hbwhelp@micrel.com
or (408) 955-1690
传感器
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