sm840051 Micrel Semiconductor, sm840051 Datasheet

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sm840051

Manufacturer Part Number
sm840051
Description
Gigabit Ethernet Ultra-low Jitter Clock Synthesizer
Manufacturer
Micrel Semiconductor
Datasheet
General Description
The SM840051 clock synthesizer was designed for
Ethernet standards. The SM840051 is optimized for 77.76,
78.125, 80.56, 155.52, 156.25, and 161.13MHz, using a
crystal at 1/8th the output frequency. The SM840051
includes a unique power reduction methodology, along
with a patented RotaryWave™ architecture, that provides
a stable clock with very low noise for optimized
performance. This yields an overall improved Bit Error
Rate (BER) and improved waveform integrity.
Power supplies of either 3.3V or 2.5V are supported, with
superior jitter and phase noise performance. An FSEL pin
supports 4x or 8x multiplication of the crystal frequency.
The SM840051 provides ultra-low jitter, and consumes low
power.
Datasheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
____________________________________________________________________________
Block Diagram
RotaryWave is a trademark of Multigig, Inc.
May 2010
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (
Features
• Generates a single LVCMOS/LVTTL output
• Output Frequencies: 77.76, 78.125, 80.56, 155.52,
• RMS Phase Jitter at 156.25MHz( 1.875MHz-20MHz):
• Integrated loop filter components
• Operates with either a 3.3V or 2.5V supply
• Power consumption is <77mA @ 3.3 V
• Fundamental parallel resonant crystal
• Crystal Frequencies: 20.141601MHz,19.53125MHz, and
• Industrial temperature range: –40°C to +75°C
• Available in 8-pin TSSOP package
Applications
• 10 Gigabit Ethernet
• SONET/SDH
408
10 Gigabit Ethernet Ultra-Low Jitter Clock
156.25, and 161.13MHz
58fs (typical)
19.44MHz
) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
SM840051
Synthesizer
hbwhelp@micrel.com
or (408) 955-1690
M9999-050710-C

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sm840051 Summary of contents

Page 1

... Rate (BER) and improved waveform integrity. Power supplies of either 3.3V or 2.5V are supported, with superior jitter and phase noise performance. An FSEL pin supports multiplication of the crystal frequency. The SM840051 provides ultra-low jitter, and consumes low power. Datasheets and support documentation can be found on Micrel’s web site at: www.micrel.com. ...

Page 2

... Pin Configuration Pin Description Pin Number Pin Name 1 VDDA XTAL OUT 4 XTAL IN 5 FSEL 6 GND VDD Configuring the SM840051 (Frequency Table) Xtal Frequency (MHz) 20.141601 20.141601 19.53125 19.53125 19.44 19.44 Output Enable OE Output 0 Disable 1 Enable May 2010 Package Operating Range Type K-8 -40° ...

Page 3

... 2.5V ± 3.3V ± 2.5V ± 3.3V ± 2.5V ±5% DD Output Enable input Output Enable input FSEL input FSEL input 3 SM840051 (2) )............................. +2.375V to +3.465V IN ) .......................... –40°C to +75°C A ).....................................................150°C/W JA Min Typ Max 2.375 2.50 2.625 2.375 2.50 2.625 Min Typ Max 3 ...

Page 4

... Condition Integration Range: 1.875M to 20MHz 20% to 80% Unit -85 dBc/Hz -122 dBc/Hz -130 dBc/Hz -127 dBc/Hz -140 dBc/Hz -165 dBc/Hz -166 dBc/Hz Min Typ Fundamental Parallel Resonant 19.44 4 SM840051 Min Typ Max 77.76 162.4 58 100 350 Max Units 20.3 MHz 50 Ω M9999-050710-C hbwhelp@micrel.com ...

Page 5

... A single LVCMOS output, capable of driving a 50 ohm load, is provided, which may be tri-stated by the OE input. The design of the SM840051 consumes very low power in the PLL due to a patented technology in the VCO and the associated dividers. The VCO range is ~3.2GHz to 3.5GHz ...

Page 6

... Micrel, Inc. Switching Waveforms May 2010 6 hbwhelp@micrel.com SM840051 M9999-050710-C or (408) 955-1690 ...

Page 7

... Micrel, Inc. Power Supply Filtering The SM840051 provides separate power supply pins to isolate any high switching noise from outputs to internal core blocks. VDD and VDDA should be individually connected to the power plane through vias. Bypass capacitors should be used for each pin. Figure 2, illustrates how the power supply filter for 3 ...

Page 8

... Cb1 + Cd1) May 2010 Example 18pF 2pF 4pF Trim Cap = (18pF) - (2pF +4pF) = 30pF The SM840051 has been characterized with 19.44MHz, 1 18pF parallel resonant crystal. The trim capacitors Ct1 and Ct2 were optimized to minimize the ppm error. (Ct2 + Cb2 + Cd2) To minimize the board capacitance, a short trace from pin to crystal footprint without vias is desirable ...

Page 9

... Micrel, Inc. Board Layout May 2010 9 hbwhelp@micrel.com SM840051 M9999-050710-C or (408) 955-1690 ...

Page 10

... 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 May 2010 8-Pin TSSOP (K-8) indemnify Micrel for any damages resulting from such use or sale. © 2010 Micrel, Incorporated. 10 SM840051 M9999-050710-C hbwhelp@micrel.com or (408) 955-1690 ...

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