1:2 Differential PECL/LVPECL/ECL Fanout Bufferww1.microchip.com/downloads/en/DeviceDoc/sy89311u_eb.pdfU1 SY89311U Micrel(4) 1:2 Differential PECL/LVPECL/ECL Fanout Buffer 1 +2.5V AC-Coupled

August 2004 [email protected] or (408) 955-1690

1:2 Differential PECL/LVPECL/ECLFanout Buffer

SY89311U Evaluation Board

General DescriptionThe SY89311U evaluation board is designed forconvenient setup and quick evaluation of theSY89311U. It allows the user to evaluate the partover the full voltage range of the part.The evaluation board standard configuration is AC-coupled for direct interface to a 50Ω compatibleoscilloscope without split supplies. For applicationsthat require a DC-coupled configuration, step-by-stepinstructions for modifying the board are included.The board is fully assembled and tested and isaccompanied with all necessary documentation.Data sheets and support documentation can be foundon Micrel’s web site at www.micrel.com.

Features• SY89311U• Single +2.5V, +3.3V or +5V 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-coupled operation

Related Documentation• SY89311U, 2.5V/3.3V/5V 1:2 Differential

PECL/LVPECL/ECL Fanout Buffer Data Sheet

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Evaluation Board

Micrel SY89311U Evaluation Board


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Evaluation Board DescriptionThe SY89311U evaluation board is initially configuredfor +3.3V operation. The board can be easily modifiedfor +2.5V or +5V operation.The default configuration for the board is the AC-coupled configuration and all boards are shipped withthis configuration. The choice between twoconfigurations offers the user flexibility in selecting theboard that is right for his particular application.AC-Coupled Evaluation BoardThe AC-coupled configuration is suited to mostcustomer applications and is preferred by the majorityof users because of its ease-of-use. It requires only asingle power supply and offers the most flexibility ininterfacing to a variety of signal sources.The DC-bias levels and AC-coupling capacitors aresupplied on-board for each input, making itunnecessary to vary the offset voltage or change anycomponents on the board as the power supplyvoltage varies over the +3.3V +10% operating range.The user needs only to supply a minimum inputvoltage swing and the bias voltage will automaticallyadjust the input to the correct level as the powersupply voltage varies.To modify the +3.3V AC-coupled evaluation boardinto a +2.5V or +5V AC-coupled evaluation board,resistor values for R9, R10, R11 and R12 at theinputs and R2, R4, R6 and R8 at the outputs need tobe changed as shown in the following table.

VCC R2-R8 R9/R11 R10/R12

2.5V 82Ω 104Ω 96Ω

3.3V 82Ω 82Ω 130Ω

5.0V 180Ω 68Ω 192Ω

Table 1. Resistor Values

DC-Coupled Evaluation BoardFor DC-coupled operation, the board can be modifiedto use two power supplies in a “split-supplyconfiguration.” The term split-supply simply meansthe +3.3V supply is split into a +2V and –1.3V, the+2.5V supply is split into a +2V and –0.5V, or for a+5V supply it is split into a +2V and –3V power supplyconfiguration. This effectively offsets the board by+2V. The +2V offset in this two-power supplyconfiguration then provides the correct terminationsfor the device by setting the Ground potential on theboard to be exactly 2 volts below the VCC supply. TheVEE voltage is then set to the appropriate negativevoltage so the device power pins still see a full 2.5V,3.3V or 5V potential between VCC and VEE.Step-by-step instructions for modifying an AC-coupledevaluation board for DC-coupled operation aresupplied in the “Modifying your AC-Coupled Board forDC-Coupled Operation” section.



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AC-Coupled Evaluation Board(Default +3.3V Configuration)

I/O Power Supply VCC GND VEE

AC-Coupled Input/AC-Coupled Output 2.5V System +2.5V 0V 0VAC-Coupled Input/AC-Coupled Output 3.3V System +3.3V 0V 0VAC-Coupled Input/AC-Coupled Output 5V System +5V 0V 0V

Table 1. AC-Coupled Evaluation Board Power Supply Connections



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Bill of MaterialsAC-Coupled Evaluation Board (Default +3.3V)

Item Part Number Manufacturer Description Qty.C1, C2, C3,C4, C5, C6

VJ0402Y104KXXAT Vishay(1) 0.1µF, 25V, 10% Ceramic Capacitor, Size 0402,X7R Dielectric

6

C7, C8 VJ0402Y103KXXAT Vishay(1) 0.01µF, 25V, 10% Ceramic Capacitor, Size 0402,X7R Dielectric

2

C9 293D685X0025BT Vishay(1) 6.8µF, 20V, Tantalum Electrolytic Capacitor, Size C 1

C10 VJ0805Y103KXXAT Vishay(1) 0.01µF, 25V, 10% Ceramic Capacitor, Size 0805 1

R2, R4, R6,R8, R9, R11,R13, R14,R15, R16

CRCW040282R5F Vishay(1) 82Ω, 1/16W, 5% Thick-film Resistor, Size 0402 10

R10, R12 Vishay(1) 130Ω, 1/16W, 5% Thick-film Resistor, Size 0402 2

R8 180Ω, 1/16W, 5% Thick-film Resistor, Size 0402 4J1 5011K-ND Digi-Key(2) PC Test point Multi-purpose Black 1

J3 5010K-ND Digi-Key(2) PC Test point Multi-purpose Red 1

SMA1, SMA2,SMA3, SMA4,SMA6, SMA7

142-0701-851 JohnsonComponents(3)

Jack Assembly End Launch SMA 6

U1 SY89311U Micrel(4) 1:2 Differential PECL/LVPECL/ECL Fanout Buffer 1

+2.5V AC-Coupled Evaluation BoardItem Part Number Manufacturer Description Qty.R9, R11 CRCW04021040F Vishay(1) 104Ω, 1/16W, 5% Thick-film Resistor, Size 0402 2

R10, R12 CRCW0402960F Vishay(1) 96Ω, 1/16W, 5% Thick-film Resistor, Size 0402 2

+5.0V AC-Coupled Evaluation BoardItem Part Number Manufacturer Description Qty.R2, R4,R6, R8

CRCW04021800F Vishay(1) 180Ω, 1/16W, 5% Thick-film Resistor, Size 0402 4



Notes:1. Vishay: www.vishay.com2. Digi-Key: www.digikey.com3. Johnson Components: www.johnsoncomponents.com4. Micrel, Inc.: www.micrel.com



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AC-Coupled Evaluation Board SetupSetting Up the AC-coupled Evaluation BoardThe following steps describe the procedure for settingup the evaluation board:

1. Set the voltage setting for a DC supply to beeither 3.3V or 5.0V depending on yourapplication and turn off the supply.

2. Connect the GND terminal to the negativeside of a DC power supply. This is the 0Vground potential.

3. Connect the VCC terminal to the positive sideof a DC power supply

4. Turn on the power supply and verify that thepower supply current is <100mA.

5. Turn off the power supply.6. Using a differential signal source set the

amplitude of each side of the differential pairto be 800mV (1600mV measureddifferentially). Set the offset to be a positivevalue, the value of this offset is not critical,as the AC-coupled inputs will beautomatically biased to the correct offset.Turn off or disable the outputs of the signalsource.

7. Using equal length 50Ω impedance coaxialcables, connect the signal source to theinputs on the evaluation board (SMA2 andSMA3).

8. Using equal length 50Ω impedance coaxialcables, connect the outputs of the evaluationboard (SMA1, SMA2, SMA3 and SMA4) tothe oscilloscope or other measurementdevice that has an internal 50Ω termination.

9. Turn on the power and verify the current is<100mA.

10. Enable the signal source and monitor theoutputs.

Evaluation Board LayoutPC Board LayoutThe evaluation boards are constructed with Rogers4003 material and are coplanar in design fabricatedto minimize noise, achieve high bandwidth andminimize crosstalk.

L1 Signal/GNDL2 Impedance GNDL3 VCC Power/VEE PowerL4 Signal/GND

Table 2. Layer Stack



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Modifying DC-Coupled Outputsfor AC-Coupled OperationWhen DC-coupling is NecessaryFor applications where AC-coupling is notappropriate, the board can be reconfigured for DC-coupled operation. An example where DC-coupling isrequired is if the input data or clock can be disabled.This would result in a DC-signal at the inputs and theon-board biasing resistors (R9, R10, R11 and R12)would apply the same level to both the true andcomplement inputs. Since these inputs are differentialthis would result in an intermediate non-differentialstate at the inputs and the outputs would be in anindeterminate condition. Reconfiguring the board forDC-coupled operation and using two power suppliescan avoid this condition.Reconfiguring an AC-Coupled Board into a DC-Coupled BoardThe following procedure details the steps forconverting an AC-coupled board to a DC-coupledboard:

1. Remove resistors R2, R4, R6, R8, R9, R10,R11 and R12.

2. Add in resistors R17 and R18 as shown inthe loading diagram.

3. Replace capacitors C1, C2, C3 and C4, C5and C6 with 0Ω resistors.

4. Remove the soldered-wire shorting barbetween J2 (VEE) and the ground plane.

5. Install components J2, C11 and C12. Theselocations should look like the components inJ3, C9 and C10.

6. For easy identification, remove the solderdot from the adjacent AC-coupled silkscreenlabel on the front of the board and add asolder dot to the DC-coupled.

Setting Up the DC-coupled Evaluation BoardThe follow steps describe the procedure for setting upthe DC-coupled evaluation board:

1. Set the voltage for DC supply number 1 tobe 2.0V and connect it to J3 (VCC).

2. Set the voltage for DC supply number 2 tobe –1.3V (for 3.3V operation), –0.5V (for2.5V operation) or –3.0V (for 5.0V operation)and connect it to J3 (VEE).

3. Connect the negative side of power supply 1to the positive side of power supply 2. Thisis the 0V ground potential for the board.

4. Turn off the power supplies and connect theGND terminal on the board to the negativeside of a DC power supply 1 and the positiveside of DC power supply 2

5. Turn on the power supply and verify that thepower supply current is <100mA. Using avoltmeter.

6. Turn off the power supply.7. Disable the outputs of the differential signal

source and set the VOH = VCC–1.0V and theVOL = VCC–1.75V) as shown in the followingtable.

I/O VoltageLevel

+2.5VSupply

+3.3VSupply

+5.0VSupply

VOH = VCC–1.0V +1.0V +1.0V +1.0VVOL = VCC–1.75V +0.25V +0.25V +0.25V

Table 3. Power Supply Table

8. Using equal length 50Ω impedance coaxialcables, connect the signal source to theinputs on the evaluation board (SMA6 andSMA7).

9. Using equal length 50Ω impedance coaxialcables, connect the outputs of the evaluationboard (SMA1, SMA2, SMA3 and SMA4) tothe oscilloscope or other measurementdevice that has an internal 50Ω termination.

10. Turn on the power and verify the current is<100mA.

11. Enable the signal source and monitor theoutputs.



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DC-Coupled Evaluation Board(Default +3.3V Configuration)

I/O Power Supply VCC GND VEE

AC-Coupled Input/AC-Coupled Output 2.5V System +2V 0V –0.5VAC-Coupled Input/AC-Coupled Output 3.3V System +2V 0V –1.3VAC-Coupled Input/AC-Coupled Output 5V System +2V 0V –3.0V

Table 4. DC-Coupled Evaluation Board Power Supply Connections



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Loading Diagram Showing Modifications for DC-Coupled Board



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Bill of MaterialsDC-Coupled Evaluation Board

Item Part Number Manufacturer Description Qty.C1, C2, C3,C4, C5, C6

CRCW04020R00F Vishay(1) Replace capacitors with resistors: 0Ω, 1/16W, 5%Thick-film Resistor, Size 0402

4

C11 293D685X0025BT Vishay(1) 6.8µF, 20V, Tantalum Electrolytic Capacitor, Size C 1

C12 VJ0805Y103KXXAT Vishay(1) 0.01µF, 25V, 10% Ceramic Capacitor, Size 0805 1

R17, R18 CRCW040249R9F Vishay(1) 49.9Ω, 1/16W, 5% Thick-film Resistor, Size 0402 1

J2 5011K-ND Digi-Key(2) PC Test Point Multi-purpose Red 1

Notes:1. Vishay: www.vishay.com2. Digi-Key: www.digikey.com



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Micrel Cross ReferenceTo find an equivalent Micrel part, go to Micrel’swebsite at: http://www.micrel.com and following thesteps below:

1. Click on Dynamic Cross Reference2. Enter competitor’s part number in the

Dynamic Cross Reference field3. To download a PDF version of this

information, click on the Cross ReferencePDF tab

HBW SupportHotline: 408-955-1690Email Support: [email protected]

Application Hints and NotesFor application notes on high speed termination onPECL and LVPECL products, clock synthesizerproducts, SONET jitter measurement, and other HighBandwidth product go to Micrel Semiconductorswebsite at http://www.micrel.com/. Once in Micrel’swebsite, follow the steps below:

1. Click on “Product Info”.2. In the Applications Information Box, choose

“Application Hints and Application Notes.

MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USATEL +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 forits 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 aproduct can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended forsurgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significantinjury 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 riskand Purchaser agrees to fully indemnify Micrel for any damages resulting from such use or sale.

© 2004 Micrel, Incorporated.

Documents

1:2 Differential PECL/LVPECL/ECL Fanout Bufferww1.microchip.com/downloads/en/DeviceDoc/sy89311u_eb.pdfU1 SY89311U Micrel(4) 1:2 Differential PECL/LVPECL/ECL Fanout Buffer 1 +2.5V AC-Coupled