SM843251-156
ClockWorks™ 10-Gigabit Ethernet,
156.25MHz, Ultra-Low Jitter LVPECL Clock
Frequency Synthesizer
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
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
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Block Diagram
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Ordering Information(1)
Part Number Package Type Operating Range Packag e Marking
SM843251-156KA K-8 Industrial 843251-156
SM843251-156KA TR(2) K-8 Industrial 843251-156
Notes:
1. Devices are Green-, RoHS-, and PFOS-compliant.
2. Tape and Reel.
Pin Configur ation
8-Pin TSSOP (K-8)
Pin Description
Pin Number Pin Name Type Level Pin Function
1 VDDA PWR Analog 2.5V or 3.3V Power Supply. No filter resistor needed.
2 VEE PWR Ground.
3 XTAL_OUT O, (SE) 12pF crystal Crystal Reference Output, no load caps needed.
4 XTAL_IN I, (SE) 12pF crystal Crystal Reference Input, no load caps needed.
5 NC
− No Connect
6 /Q0 O, (DIF) LVPECL Differential Clock Output
7 Q0 O, (DIF) LVPECL Differential Clock Output
8 VDD PWR 2.5V or 3.3V Power Supply
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Absolute Maximum Ratings(1)
Supply Voltage (VDDA, VDD,) ........................................+4.6V
Input Voltage (VIN) ...............................−0.50V to VDD + 0.5V
LVPECL Output Current (IOUT)
Continuous............................................................50mA
Surge ..................................................................100mA
Lead Temperature (soldering, 20sec.)....................... 260°C
Case Temperature ..................................................... 115°C
Storage Temperature (Ts) .........................−65°C to +150°C
Operating Ratings(2)
Supply Voltage (VDD, VDDA) ........................+2.375 to +3.465
Ambient Temperature (TA) ..........................–40°C to +85°C
Junction Thermal Resistance
TSSOP (θJA)(Still Air).......................................141°C/W
DC Electrical Characteristics(3)
VDD = VDDA = 3.3V ±5%; TA = –40°C to +85°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
VDD Core Supply Voltage 3.135 3.30 3.465 V
VDDA Analog Supply Voltage 3.135 3.30 3.465 V
IDDA Analog Supply Current Included in IEE 50 60 mA
IEE Total Supply Current No load 88 110 mA
VDD = VDDA = 2.5V ±5%; TA = –40°C to +85°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
VDD Core Supply Voltage 2.375 2.50 2.625 V
VDDA Analog Supply Voltage 2.375 2.50 2.625 V
IDDA Analog Supply Current Included in IEE 50 60 mA
IEE Total Supply Current No load 80 100 mA
LVPECL DC Electrical Char acteristics(3, 4)
VDD = VDDA = 2.5V ±5% or 3.3V ±5%, TA = –40°C to +85°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
VOH Output High Voltage 50Ω to VDD − 2V VDD – 1.145 VDD – 0.97 VDD – 0.845 V
VOL Output Low Voltage 50Ω to VDD − 2V VDD – 1.945 VDD – 1.77 VDD – 1.645 V
VSWING Peak-to-Peak Output Voltage Swing 0.6 0.8 1.0 V
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.
2. The data sheet limits are not guaranteed if the device is operated beyond the operating ratings.
3. 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.
4. See Figure 4 for load test circuit example.
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AC Electrical Characteristics(5)
VDD = VDDA = 2.5V ±5% or 3.3V ±5%, TA = –40°C to +85°C, unless noted.
Symbol Parameter Condition Min. Typ. Max. Units
FOUT Output Frequency 25MHz Crystal 156.25 MHz
tJITTER RMS Phase Jitter (Output = 156.25 MHz) Integration Range: 1.875MHz to 20MHz 110 fs
tR / tF Output Rise/Fall Time 20% to 80% 80 175 350 ps
ODC Output Duty Cycle 48 50 52 %
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.
Crystal Characteristics
Parameter Condition Min. Typ. Max. Units
Mode of Oscillation 12pF Load Fundamental, Parallel Resonant
Frequency 25 MHz
Equivalent Series Resistance (ESR) 50 Ω
Shunt Capacitor, C0 3 7 pF
Correlation Drive Level 100 300 uW
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Figure 1. Duty Cycle Timing
Figure 2. All Outputs Rise/Fall Time
Figure 3. RMS Phase Noise/Jitter
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Figure 4. LVPECL Output Load and Test Circuit
Figure 5. Crystal Input Interface
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Package Information
8-Pin TSSOP (K-8)
MICREL, INC. 2180 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL +1 (408) 944-0800 FAX +1 (408) 474-1000 WEB http://www.micrel.com
Micrel makes no representations or warranties with respect to the accuracy or completeness of the information furnished in this data sheet. This
information is not intended as a warranty and Micrel does not assume responsibility for its use. Micrel reserves the right to change circuitry,
specifications and descriptions at any time without notice. No license, whether express, implied, arising by estoppel or otherwise, to any intellectual
property rights is granted by this document. Except as provided in Micrel’s terms and conditions of sale for such products, Micrel assumes no liability
whatsoever, and Micrel disclaims any express or implied warranty relating to the sale and/or use of Micrel products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical impla
into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A
Purchaser’s use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser’s own risk and Purchaser agrees to fully
indemnify Micrel for any damages resulting from such use or sale.
can nt
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or (408) 955-1690
