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SM840051
10 Gigabit Ethernet Ultra-Low Jitter Clock Synthesizer
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 RotaryWaveTM 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.
Features
* Generates a single LVCMOS/LVTTL output * Output Frequencies: 77.76, 78.125, 80.56, 155.52, 156.25, and 161.13MHz * RMS Phase Jitter at 156.25MHz( 1.875MHz-20MHz): 58fs (typical) * 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 19.44MHz * Industrial temperature range: -40C to +75C * Available in 8-pin TSSOP package
Applications
* 10 Gigabit Ethernet * SONET/SDH
____________________________________________________________________________ Block Diagram
RotaryWave is a 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
May 2010
M9999-050710-C hbwhelp@micrel.com or (408) 955-1690
Micrel, Inc.
SM840051
Ordering Information(1)
Part Number SM840051KA SM840051KA TR
Note: 1. Devices are Green, RoHS-compliant and PFOS-compliant. 2. Tape and Reel.
(2)
Package Type K-8 K-8
Operating Range -40C to +75C -40C to +75C
Package Marking 840051 840051
Lead Finish NiPdAu NiPdAu
Pin Configuration
8-Pin TSSOP (K-8)
Pin Description
Pin Number 1 2 3 4 5 6 7 8 Pin Name VDDA OE XTAL OUT XTAL IN FSEL GND Q0 VDD Type P I O I I P O P Pull down Pull-up Level Pin Function Analog power. Output Enable: 1 = Enable, 0 = Disable. Crystal Output. Crystal Input. Frequency Select Pin. Ground. Single Ended LVCMOS Clock Out. Core Power.
Configuring the SM840051 (Frequency Table)
Xtal Frequency (MHz) 20.141601 20.141601 19.53125 19.53125 19.44 19.44 FSEL 0 1 0 1 0 1 Output Frequency (MHz) 161.132812 80.566406 156.25 78.125 155.52 77.76
Output Enable
OE 0 1 Output Disable Enable
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Micrel, Inc.
SM840051
Absolute Maximum Ratings(1)
Supply Voltage (VDD)...................................................+4.6V Input Voltage (VIN) ................................ -0.50V to VDD+0.5V Output Voltage (VOUT) .......................... -0.50V to VDD+0.5V Lead Temperature (soldering, 20sec.)....................... 260C Storage Temperature (Ts) .........................-65C to +150C
Operating Ratings(2)
Supply Voltage (VIN)............................. +2.375V to +3.465V Ambient Temperature (TA) .......................... -40C to +75C Junction Thermal Resistance TSSOP (JA).....................................................150C/W
DC Electrical Characteristics
VDD = 2.5V 5%; TA = -40C to +75C, unless noted.
Symbol VDD VDDA IDD IDDA Parameter Core Supply Voltage Analog Supply Voltage Core Supply Current Analog Supply Current No load Condition Min 2.375 2.375 Typ 2.50 2.50 12 48 Max 2.625 2.625 20 55 Units V V mA mA
DC Electrical Characteristics
VDD = 3.3V 5%; TA = -40C to +75C, unless noted.
Symbol VDD VDDA IDD IDDA Parameter Core Supply Voltage Analog Supply Voltage Core Supply Current Analog Supply Current No load Condition Min 3.135 3.135 Typ 3.30 3.30 15 49 Max 3.465 3.465 25 60 Units V V mA mA
LVCMOS Electrical Characteristics
VDD = 2.5V and 3.3V 5%; TA = -40C to +75C, unless noted.
Symbol VIH VIL VOH VOL IIH IIL IIH IIL
Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating.
Parameter Input HIGH Voltage Input LOW Voltage Output HIGH Voltage Output LOW Voltage Input HIGH Current Input LOW Current Input HIGH Current Input LOW Current
Condition VDD = 3.3V 5% VDD = 2.5V 5% VDD = 3.3V 5% VDD = 2.5V 5% VDD = 3.3V 5% VDD = 2.5V 5% Output Enable input Output Enable input FSEL input FSEL input
Min 2 1.7 -0.30 -0.30 2.6 1.8
Typ
Max VDD +0.3 VDD + 0.3 0.80 0.70
Units V V V V V V
0.5 5 -150 150 -5
V A A A A
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Micrel, Inc.
SM840051
AC Electrical Characteristics
VDD = 2.5V and 3.3V 5%; TA = -40C to +75C, unless noted.
Symbol FOUT tJITTER t R / tF ODC Parameter Output frequency RMS phase jitter @ 156.25MHz Output rise/fall time Output Duty Cycle Integration Range: 1.875M to 20MHz 20% to 80% 100 48 50 Condition Min 77.76 58 350 52 Typ Max 162.4 Units MHz fs ps %
Test Circuit
3.3V Carrier Frequency, 156.25MHz
Offset from Carrier 100Hz 1kHz 10kHz 100kHz 1MHz 10MHz 40MHz Measured Phase Noise -85 -122 -130 -127 -140 -165 -166 Unit dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz
Crystal Characteristics(1)
Parameter Mode of Oscillation Frequency Equivalent Series Resistance (ESR) Shunt Capacitor Drive Level
Note: 1. Devices are Green, RoHS-compliant and PFOS-compliant
Min 19.44
Typ
Max 20.3 50 7 1
Units MHz pF mW
Fundamental Parallel Resonant
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Micrel, Inc.
SM840051 providing high resolution and easy integer divide ratios. Output Divider ratios are fixed at either /20 or /40 controlled via the FSEL pin, and the feedback divider also fixed at /160. Duty Cycle is inherently improved and guarantees tight control and stability on this critical specification. This provides improved specifications for Duty Cycle, Jitter, Phase Noise, Power Consumption, and noise sensitivity. Additionally, the SM840051 will operate at either 3.3V or 2.5V supplies.
Functional Description
The SM840051 synthesizer provides a high performance solution to frequency generation. Low cost crystals of 20.141601MHz, 19.53125MHz, and 19.44MHz are used to provide low jitter output clocks of 161.132MHz, 156.25MHz , and 155.52MHz, respectively. 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
RMS Phase Noise/Jitter
Phase Noise Plot: 156.25MHz @ 3.3V
RMS Phase Jitter (Random) 1.875MHz to 20MHz = 58 fs (typical)
Noise Power dBc/Hz
(Random) 1.875MHz to 20MHz
Offset Frequency ( Hz)
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Micrel, Inc.
SM840051
Switching Waveforms
May 2010
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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 3.3V and 2.5V is configured. Crystal Loading
SM840051
Crystal Recommendations This device requires a parallel resonance crystal. Substituting a series resonance crystal will cause this device to operate at the wrong frequency and violate the ppm specifications. To achieve low ppm error, the total capacitance the crystal will see must be considered to calculate the appropriate capacitive loading (CL). Load Capacitance at each side: Trim Capacitance = Ct = (2*CL-(Cb + Cd)) CL: Crystal load capacitance. Defined by manufacturer Ct: External trim capacitors. (Trimmed CL Load capacitance to get the right ppm) Cb: Board capacitance (vias, traces, etc.) Cd: Internal capacitance of the device (lead frame, bond wires, pin, etc.)
Equivalent Series Resistance (ESR) Max. 50 Cut Load Cap. 18pF Shunt Cap. Max. 7pF Drive Max. 0.1mW
Figure 2. Power Supply Filter
AT
Crystal Input Interface
May 2010
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Micrel, Inc. Total capacitance seen by crystal = CL = 1 1 (Ct1 + Cb1 + Cd1) + 1 (Ct2 + Cb2 + Cd2)
SM840051 Example: CL = 18pF, Cb = 2pF, Cd = 4pF Trim Cap = Ct = 2 (18pF) - (2pF +4pF) = 30pF The SM840051 has been characterized with 19.44MHz, 18pF parallel resonant crystal. The trim capacitors Ct1 and Ct2 were optimized to minimize the ppm error. To minimize the board capacitance, a short trace from pin to crystal footprint without vias is desirable. It is preferable to have ground shielding or distance between the crystal traces and noisy signals on the board.
May 2010
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Micrel, Inc.
SM840051
Board Layout
May 2010
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M9999-050710-C hbwhelp@micrel.com or (408) 955-1690
Micrel, Inc.
SM840051
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
The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use. Micrel reserves the right to change circuitry and specifications at any time without notification to the customer. Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant 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. (c) 2010 Micrel, Incorporated.
May 2010
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