2.0GHz, Low Power, 1:6 LVPECL Fanout Buffer with 2:1 Input MUX and Internal Termination SY89856U Evaluation Board General Description Features The SY89856U evaluation board is designed for convenient setup and quick evaluation of the SY89856U. The board is optimized to interface directly to a 50Ω oscilloscope. For best AC performance, the board is configured in ACcoupled In and AC-coupled Out configuration. For applications that require a DC-coupled configuration, step-by-step instructions for modifying the board are included. • Fully assembled and tested SY89856U • +2.5V or +3.3V power supply • AC-coupled configuration for ease-of-use • I/O interface includes on-board termination • Fully assembled and tested • Can be reconfigured for DC-coupling operation Related Documentation • SY89856U 2.0GHz, Low Power, 1:6 LVPECL Fanout Buffer with 2:1 Input MUX and Internal Termination Data Sheet _______________________________________________________________________________________________________ Evaluation Board MLF and MicroLeadFrame are trademarks of Amkor Technology, 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 2005 M9999-031505 [email protected] or (408) 955-1690 Micrel, Inc. Evaluation Board Description The default configuration for the SY89856U board is AC-coupled. The choice between AC-coupled and DCcoupled configurations offers the user flexibility for specific applications. With the current board layout, Q0 is meant for DC-coupled operation. In default ACcoupled configuration, Q0 is not brought out. AC-Coupled Evaluation Board The AC-coupled configuration is suited to most customer applications and is preferred by the majority of users because of its ease-of-use. It requires only a single power supply and offers the most flexibility in interfacing to a variety of signal sources. The DC-bias levels and AC-coupling capacitors are supplied on-board for each input, making it unnecessary to vary the offset voltage or change any components on the board as the power supply voltage varies over the +2.5V +5% and +3.3V +10% operating range. The user needs only to supply a minimum input voltage swing and the bias voltage will automatically adjust the input to the correct level as the power supply voltage varies. March 2005 SY89856U Evaluation Board DC-Coupled Evaluation Board For applications that are not suited to AC-coupling such as clock applications that can be turned off for extended periods of time, the board can be user-configured for DC-coupled operation. This can be accomplished by modifying the board to use two power supplies into a “split-supply configuration”. Since LVPECL is referenced to VCC, and standard PECL termination is 50Ω to VCC-2V. Split-supply is an easy method to interface to a 50Ω (to ground) scope. Therefore, a 3.3V supply will be split into +2V and -1.3V, and a 2.5V supply will be split into a +2V and -0.5V. The +2V offset in this two-power supply configuration provides the correct terminations for the device by setting the Ground potential on the board to be exactly 2 volts below the VCC supply. The VEE voltage is then set to –1.3V for 3.3V devices, or –0.5V for 2.5V devices to ensure proper VCC to VEE voltage difference. Any-Input Interface The unique internal input termination sets the input common mode voltage. This enables the input to interface with any differential signal over the supply voltage without modifying the board. 2 M9999-031505 [email protected] or (408) 955-1690 Micrel, Inc. SY89856U Evaluation Board Evaluation Board AC-Coupled Evaluation Board I/O Power Supply VCC GND VEE AC-Coupled Input/AC-Coupled Output 2.5V +2.5V 0V 0V AC-Coupled Input/AC-Coupled Output 3.3V +3.3V 0V 0V Table 1. AC-Coupled Evaluation Board Power Supply Connections March 2005 3 M9999-031505 [email protected] or (408) 955-1690 Micrel, Inc. SY89856U Evaluation Board Evaluation Board DC-Coupled Evaluation Board I/O Power Supply VCC GND VEE DC-Coupled Input/DC-Coupled Output 2.5V +2.0V 0V -0.5V DC-Coupled Input/DC-Coupled Output 3.3V +2.0V 0V -1.3V Table 2. DC-Coupled Evaluation Board Power Supply Connections March 2005 4 M9999-031505 [email protected] or (408) 955-1690 Micrel, Inc. SY89856U Evaluation Board 7. Using equal length 50Ω impedance coaxial cables, connect the signal source to the inputs on the evaluation board (SMA1 and SMA2 or SMA3 and SMA4). AC-Coupled Evaluation Board Setup Setting up the SY89856U AC-coupled Evaluation Board The following steps describe the procedure for setting up the evaluation board: 1. Set the voltage setting for a DC supply to be either 2.5V or 3.3V depending upon your application and turn off the supply. 2. Connect the GND and VEE terminal to the negative side of a DC power supply. This is the 0V ground potential. 3. Connect the VCC terminal to the positive side of a DC power supply. 4. Turn on the power supply and verify the power supply current is <160mA. 5. Turn off the power supply. 6. Using a differential signal source, set the amplitude of each side of the differential pair to be 800mV (1600mV measured differentially). Set the offset to be a positive value, the value of this offset is not critical, since the AC-coupled inputs will automatically bias to the correct offset. Turn off or disable the outputs of the signal source. March 2005 8. Using equal length 50Ω impedance coaxial cables, connect the outputs of the evaluation board (SMA5 and SMA6 or SMA7 and SMA8 or SMA9 and SMA10 or SMA11 and SMA12 or SMA13 and SMA14 or to the oscilloscope or other measurement device that has an internal 50Ω termination. Any of these 10 outputs that are not connected to a scope or other instrument should be terminated with a 50Ω to ground at the SMA on the board. 9. Turn on the power supply and verify the current is <200mA. 10. Enable the signal source and monitor the outputs. 5 M9999-031505 [email protected] or (408) 955-1690 Micrel, Inc. SY89856U Evaluation Board 5. Turn on the power supply and verify that the power supply current is <160mA. Using a voltmeter. 6. Turn off the power supply. 7. Disable the outputs of the differential signal source and set the VOH = VCC–1.0V and the VOL = VCC–1.75V) as shown in the following table: Modifying AC-Coupled Outputs for DCCoupled Operation When DC-coupling is Necessary For applications when AC-coupling is not appropriate, the board can be reconfigured for DC-coupled operation. An example when DC-coupling is required is if the input data or clock can be disabled. This would result in a DC-signal at the inputs and the on-board biasing resistors (R1 and R2) would apply the same level to both the true and complement inputs. Since these inputs are differential, this would result in an intermediate non-differential state at the inputs and the outputs would be in an indeterminate condition. Reconfiguring the board for DC-coupled operation and using two power supplies can avoid this condition. Reconfiguring the AC-coupled Board into a DCcoupled Board The following procedure details the steps for converting an AC-coupled board to a DC-coupled board: I/O Voltage Level +3.3V Supply +2.5V Supply VOH = VCC–1.0V +2.3V +1.5V VOL = VCC–1.75V +1.55V +0.75V Table 3. LVPECL I/O Levels 8. Using equal length 50Ω impedance coaxial cables, connect the outputs of the evaluation board (SMA5 and SMA6 or SMA7 and SMA8 or SMA9 and SMA10 or SMA11 and SMA12 or SMA13 and SMA14 or SMA15 and SMA16) to the oscilloscope or other measurement device that has an internal 50Ω termination. Any of these 12 outputs that are not connected to a scope or other instrument should be terminated with a 50Ω termination-to-ground at the SMA on the board. 9. Turn on the power and verify the current is <200mA. 10. Enable the signal source and monitor the outputs. 1. Disconnect VREF-AC0 and VT0 2. Disconnect VREF-AC1 and VT1 3. Remove resistors R2-R11 4. Replace capacitors C1–C4 and C7–C16 with 0Ω resistors. Setting up the DC-coupled Evaluation Board The following steps describe the procedure for setting up the DC-coupled evaluation board: 1. Set the voltage for DC supply number 1 to be 2.0V and connect it to J1 (VCC). 2. Set the voltage for DC supply number 2 to be – 1.3V (for 3.3V operation) or –0.5V (for 2.5V operation) and connect it to J3 (VEE). 3. Connect the negative side of power supply 1 to the positive side of power supply 2. This is the 0V ground potential for the board. 4. Turn off the power supplies and connect the GND terminal on the board, J2, to the negative side of a DC power supply 1 and the positive side of DC power supply 2 Evaluation Board Layout PC Board Layout The evaluation board is constructed with Rogers 4003 material and is coplanar in design, fabricated to minimize noise, achieve high bandwidth and minimize crosstalk. L1 GND and Signal L2 GND L3 VCC L4 GND Table 4. Layer Stack March 2005 6 M9999-031505 [email protected] or (408) 955-1690 Micrel, Inc. SY89856U Evaluation Board Bill of Materials Item Part Number Manufacturer (1) C1-C18 C21, C22 VJ0402Y104KXXAT Vishay C19, C20 293D685X0025C2T Vishay(1) J1 J2, J3 R1 111-0702-001 111-0703-001 CRCW04023001F Description Qty. 0.1µF, 25V, 10% Ceramic Capacitor, Size 0402, X7R Dielectric 20 6.8µF, 20V, Tantalum Electrolytic Capacitor, Size C 2 Johnson (2) Red Banana Jack 1 Johnson (2) Black Banana Jack 2 (1) 3kΩ, 10%, 1/16W Resistor SMD, Size 0402 1 (1) 82Ω, 1/10W, 5% Thick-film Resistor, Size 0402 10 Jack Assembly End Launch SMA 16 Vishay R2-R11 CRCW040282R5F SMA1SMA16 142-0701-851 Johnson(2) Vishay SW1 CT2182LPST-ND DigiKey(3) 2-Position Dip 1 U1 SY89856U Micrel(4) 2.0GHz, Low-Power, 1:6 LVPECL Fanout Buffer with 2:1 Input MUX and Internal Termination 1 Additional Components for AC-Coupled Outputs Item C1-C4, C7-C18 Part Number CRCW0402000F Manufacturer (1) Vishay Description Qty. 0Ω, 1/16W, Resistor SMD, Size 0402 16 Notes: 1. Vishay: www.vishay.com. 2. Johnson: www.johnsoncomponents.com. 3. DigiKey: www.digikey.com. 4. Micrel, Inc.: www.micrel.com. March 2005 7 M9999-031505 [email protected] or (408) 955-1690 Micrel, Inc. SY89856U Evaluation Board Micrel Cross Reference Application Hints and Notes To find an equivalent Micrel part, go to Micrel’s website at: http://www.micrel.com and follow the steps below: 1. Click on Dynamic Cross Reference. 2. Enter competitor’s part number in the Dynamic Cross Reference field. 3. To download a PDF version of this information, click on the Cross Reference PDF tab. For application notes on high speed termination on PECL and LVPECL products, clock synthesizer products, SONET jitter measurement, and other High Bandwidth products go to Micrel’s website at http://www.micrel.com/. Once in Micrel’s website, follow the steps below: 1. Click on “Product Info.” 2. In the Applications Information Box, choose “Application Hints and Application Notes.” HBW Support Hotline: 408-955-1690 Email Support: [email protected] 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. © 2005 Micrel, Incorporated. March 2005 8 M9999-031505 [email protected] or (408) 955-1690