SM840021 125MHz Ultra-Low Jitter Clock Synthesizer General Description Features The SM840021 synthesizer was designed for Ethernet applications. This clock synthesizer is optimized for 125MHz using a standard 25MHz fundamental parallel resonant crystal, with unparalleled stability and accuracy over the full operating range. The SM840021 design includes a unique power reduction methodology, along with a patented RotaryWaveTM architecture that provides a very stable clock with very low noise for optimized performance yielding an overall improved Bit Error Rate (BER) and improved waveform integrity. Datasheets and support documentation can be found on Micrel’s web site at: www.micrel.com. • • • • • • • • • • Generates an optimized 125MHz LVCMOS Output Integrated loop filter components RMS Phase Jitter: 250 fs (typ) Operates with either a 3.3V or 2.5V supply Power consumption is <77mA @ 3.3V Input frequency: 25MHz parallel resonant crystal Output frequency: 125MHz Temperature range: –40°C to +75°C Green, RoHS-compliant and PFOS-compliant Available in 8-pin TSSOP package Applications • Gigabit Ethernet • Datacom/Telecom • Ethernet Switch ___________________________________________________________________________________________________________ Block Diagram 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 March 2010 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 Ordering Information(1) Part Number SM840021KA (2) SM840021KA TR Package Type Operating Range Package Marking Lead Finish K-8 -40°C to +75°C 840021 NiPdAu K-8 -40°C to +75°C 840021 NiPdAu Note: 1. Devices are Green, RoHS-compliant and PFOS-compliant. 2. Tape and Reel Pin Configuration 8-Pin TSSOP (K-8) Pin Description Pin Number Pin Name Type 1 VDDA P Level Pin Function 2 OE I 3 XTAL OUT O 4 XTAL IN I 5 NC 6 GND P 7 Q0 O Single Ended LVCMOS Clock Out. 8 VDD P Core Power. Analog Power. Pull-up Output Enable: 1 = Enable, 0 = Disable. Crystal Output. Crystal Input. No Connect. Ground. Output Enable March 2010 OE Output 0 Disable 1 Enable 2 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 Absolute Maximum Ratings(1) Operating Ratings(2) 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.)....................... 260°C Storage Temperature (Ts) .........................–65°C to +150°C Supply Voltage (VIN)............................. +2.375V to +3.465V Ambient Temperature (TA) .......................... –40°C to +75°C Junction Thermal Resistance TSSOP (θJA).....................................................150°C/W DC Electrical Characteristics VDD = 2.5V ±5%; TA = –40°C to +75°C, unless noted. Min Typ Max Units VDD Symbol Core Supply Voltage Parameter 2.375 2.50 2.625 V VDDA Analog Supply Voltage 2.375 2.50 2.625 V IDD Core Supply Current IDDA Analog Supply Current Condition No load 12 20 mA 48 55 mA Min Typ Max Units DC Electrical Characteristics VDD = 3.3V ±5%; TA = -40°C to +75°C, unless noted. Symbol Parameter VDD Core Supply Voltage 3.135 3.30 3.465 V VDDA Analog Supply Voltage 3.135 3.30 3.465 V IDD Core Supply Current IDDA Analog Supply Current Condition No load 15 22 mA 49 55 mA Typ Max Units LVCMOS DC Characteristics VDD = 2.5V ±5% and 3.3V ±5%; TA = -40°C to +75°C, unless noted. Symbol Parameter Condition Min VIH Input HIGH Voltage VIL Input LOW Voltage IIH Input HIGH Current VDD = VIN = 3.465V IIL Input LOW Current VDD = 3.465V; VIN = 0V VOH Output HIGH Voltage(3) VOL Output LOW Voltage(3) 3.3V Operation 2 VDD +0.3 V 2.5V Operation 1.7 VDD + 0.3 V 3.3V Operation -0.3 0.8 V 2.5V Operation -0.3 0.7 V 5 µA -150 µA VDD = 3.3V ±5% 2.6 V VDD = 2.5V ±5% 1.8 VDD = 3.3V ±5% or VDD = 2.5V ±5% V 0.5 V Notes: 1. Exceeding the absolute maximum rating may damage the device. 2. The device is not guaranteed to function outside its operating rating. 3. Outputs terminated with 50Ω to VDD/2. See Parameters measurements 3.3V load test circuit. March 2010 3 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 AC Electrical Characteristics VDD = 2.5V ±5% and 3.3V ±5%; TA = -40°C to +75°C, unless noted. Symbol Parameter Condition FOUT Output Frequency 25MHz Crystal Min Typ Max 125 tJITTER RMS phase jitter @ 125MHz Integration Range: 1.875MHz to 20MHz t R / tF Output Rise/Fall Time 20% to 80% ODC Output Duty Cycle MHz 250 100 48 50 Units fs 350 ps 52 % Test Circuit 3.3V Carrier Frequency, 125MHz Offset from Carrier Measured Phase Noise Unit 100Hz -103 dBc/Hz 1kHz -126 dBc/Hz 10kHz -134 dBc/Hz 100kHz -130 dBc/Hz 1MHz -143 dBc/Hz 1.875MHz -152 dBc/Hz 10MHz -166 dBc/Hz 20MHz -167 dBc/Hz March 2010 4 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 Functional Description providing a precision clock at 125MHz. Duty Cycle is inherently improved to provide a tight control and stability on this critical specification. The device provides improved specifications for Duty Cycle, Jitter, Phase Noise, Power Consumption, and noise sensitivity. Additionally, the SM840021 will operate at either 3.3V or 2.5V supplies. The SM840021 provides a high performance and high accuracy solution for a precision clock source at 125MHz derived, from a low cost 25MHz Xtal. The design of the SM840021 consumes very low power in the PLL due to a proprietary technology in the VCO and the associated dividers. The output divider is fixed at ÷26, and the feedback divider is also fixed at ÷130 March 2010 5 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 RMS Phase Noise/Jitter Phase Noise Plot: 125MHz @ 3.3V March 2010 6 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 Switching Waveforms March 2010 7 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 Power Supply Filtering The SM840021 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 3.3 V and 2.5 V is configured. Crystal Loading 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 of the crystal must be considered in order to calculate 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.) Figure 2. Equivalent Series Resistance (ESR) Max. Cut 70Ω AT Load Cap. Shunt Cap. Max. Drive Max. 7pF 0.1mW Crystal Input Interface March 2010 8 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 Total capacitance seen by crystal = CL = Example: CL = 18pF, Cb = 2pF, Cd = 4pF Trim Cap = Ct = 2 (18pF) - (2pF +4pF) = 30pF The SM840021 has been characterized with 25MHz, 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. 1 1 (Ct1 + Cb1 + Cd1) + 1 (Ct2 + Cb2 + Cd2) Board Layout March 2010 9 M9999-031810-B [email protected] or (408) 955-1690 Micrel, Inc. SM840021 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. © 2010 Micrel, Incorporated. March 2010 10 M9999-031810-B [email protected] or (408) 955-1690