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| 19-1644; Rev 0; 1/00 MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit General Description The MAX3296 shortwave or vertical cavity-surface emitting laser (VCSEL) evaluation kit (EV kit) is an assembled, surface-mount demonstration board that allows easy optical and electrical evaluation of the MAX3286 1.25Gbps laser driver or the MAX3296 2.5Gbps laser driver in the common-cathode configuration. Shortwavelength laser diodes (wavelength 980nm) and VCSELs typically require a common-cathode configuration. In the common-cathode configuration, the laser's cathode connects to ground and the laser is driven at its anode. The MAX3296 shortwave or VCSEL EV kit regulates the laser bias current to keep a constant photodiode current or the kit directly senses the laser bias current and holds it constant. Refer to the MAX3296EVKIT-LW for evaluation of the MAX3286/MAX3296 with long-wavelength laser diodes in the common-anode configuration. o Drives Common-Cathode Lasers o Includes Socket for Laser Insertion o LED Fault Indicator o Evaluates Either MAX3286 or MAX3296 (installed) o Adjustable DC Bias Current for VCSELs o Adjustable Photodiode Current o Adjustable Modulation Current o Adjustable Modulation Current Tempco o Configured for Electrical Operation, No Laser Necessary Features Evaluates: MAX3286/MAX3296 Ordering Information PART MAX3296EVKIT-SW TEMP. RANGE 0C to +70C IC PACKAGE 32 TQFP Component List DESIGNATION QTY C1-C5, C13, C14, C22, C25, C26 C11 C12 C23 D1 D3 J1, J2, J5 10 DESCRIPTION 0.01F 10%, 16V min, X7R ceramic capacitors (0402) 0.1F 10%, 16V min, X7R ceramic capacitor (0402) Open, user supplied (0402)* 10F 10%, 16V tantalum capacitor AVX TAJC106K016 Open, user supplied (laser diode and photodiode assembly; see Figure 1) Red LED SMA connectors (edge mount) EFJohnson 142-0701-801 or Digi-Key J502-ND Test points Mouser 151-203 2-pin headers (0.1in centers) Digi-Key S1012-36-ND Ferrite beads Murata BLM11HA102SG Ferrite bead Murata BLM11HA601SG R5 R9, R30 R10 R11 R12 R13 R20 R22 1 2 1 1 1 1 1 1 DESIGNATION QTY L8 Q1 1 0 1 0 1 3 Q2 Q4 R2 R3 R4 1 0 1 1 1 1 1 DESCRIPTION Ferrite bead (included but not installed) Murata BLM11HA102SG Open Zetex FMMT491A Zetex FMMT591A 115 1% resistor (0402) 100k variable resistor Bourns or Digi-Key 3296W-104-ND 50k variable resistor Bourns or Digi-Key 3296W-503-ND 10k variable resistor Bourns or Digi-Key 3296W-103-ND 1k 5% resistors (0402) 5.1k 5% resistor (0402) 200 variable resistor Bourns or Digi-Key 3296W-201-ND 0 resistor (0402) 24.9 1% resistor (0402)* 49.9 1% resistor (0402) 36 5% resistor (0603) J7, J8 JU1-JU5 L1, L2 L4 2 5 2 1 Component List continues on next page. *These components are part of the compensation network, which reduces overshoot and ringing. Parasitic series inductance introduces a zero into the laser's frequency response. R13 and C12 add a pole to cancel this zero. The optimal values depend upon the laser used. Maxim recommends R13 = 24.9 and C12 = 2pF as a starting point. ________________________________________________________________ Maxim Integrated Products 1 For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769. MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3286/MAX3296 Component List (continued) DESIGNATION QTY R23 R24 R25 TP1, TP3, TP4, TP9, TP10, TP14, TP15, TP19, TP20 U1 U1 U2 1 1 1 9 1 1 1 DESCRIPTION 0 resistor (0603) 24.9 1% resistor (0402) 511 1% resistor (0402) Test points Mouser 151-203 MAX3296CHJ (32-pin TQFP) MAX3286CHJ (32-pin TQFP, included but not installed) MAX4322EUK (5-pin SOT23) Evaluating the MAX3286 The MAX3296 shortwave EV board can easily be modified to accommodate the MAX3286. Desolder and remove the MAX3296 (the EV board ships with the MAX3296 installed), and replace it with the MAX3286 (included with the EV kit). No other circuit modifications are necessary. Electrical Quick Start Electrical Quick Start with Simulated Photodiode Feedback 1) Configure the board so that it will servo the DC bias current, achieving a fixed photodiode current and activating the photodiode emulator circuit. Set up the following shunts: SHUNT SP3 SP4 SP5 SP6 SP7 SP8 SP9 SP10 SP11 STATUS Open Closed Closed Closed Closed Closed Open Open Closed 2) Make sure nothing is installed in the laser socket (Figure 1). 3) Confirm that R24 is installed. 4) Make sure L8 is not installed. 5) Confirm that C12 is open. Without a laser installed, no compensation network is necessary. 6) Set potentiometer R5 (RSET) to midscale by turning the screw counterclockwise until a faint click is felt, then clockwise for 15 full revolutions (30 full revolutions in the 0 to 10k range of the multiturn potentiometer). This sets the regulation point for the simulated photodiode current to (2.65V - 1.7V) / 5k = 190A. The photodiode emulator circuit regulates the DC bias current out of Q4 to 28 x 190A 5mA. 7) Set potentiometer R4 (RMOD) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 50k range of the multiturn potentiometer). This minimizes the modulation current. 8) Set potentiometer R3 (RTC) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 100k range of the multiturn potentiometer). This minimizes the temperature coefficient (tempco) of the modulation current. 9) Set potentiometer R11 to 30 of resistance by turning the screw clockwise until a faint click is felt, then counterclockwise for five turns. 10) Place jumpers across JU2 (EN), JU3 (EN), and JU4 (PORDLY). 11) If you intend to power the board from a +5V supply, place a jumper across JU1 (LV). Do not apply power yet. 12) Make sure there is no jumper on JU5 (FLTDLY). 13) Attach a cable with 50 characteristic impedance between the J5 SMA output connector and the input of the oscilloscope. Make sure the oscilloscope input is 50 terminated. 14) Attach differential sources to SMA connectors J1 and J2. Each source should have a peak-to-peak amplitude between 100mV and 830mV. 15) Apply either +3.3V or +5V power to the board at the J7 (VCC) and J8 (GND) test points. Set the current limit to 300mA. 16) While monitoring the voltage on TP19, adjust R5 (RSET) until the desired DC bias current is obtained. Turning the R5 potentiometer screw clockwise increases the DC bias current. Refer to the MAX3286/MAX3296 Common-Cathode Laser with Photodiode application circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet. 2 _______________________________________________________________________________________ MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit 17) While monitoring the J5 SMA connector output on the oscilloscope, adjust R4 (RMOD) until the desired modulation current is obtained. Turning the R4 potentiometer screw clockwise increases the modulation current. 9) Place jumpers across JU2 (EN), JU3 (EN), and JU4 (PORDLY). 10) If you intend to power the board from a +5V supply, place a jumper across JU1 (LV). Do not apply power yet. 11) Make sure there is no jumper on JU5 (FLTDLY). 12) Attach a cable with 50 characteristic impedance between the J5 SMA output connector and the input of the oscilloscope. Make sure the oscilloscope input is 50 terminated. 13) Attach differential sources to SMA connectors J1 and J2. Each source should have a peak-to-peak amplitude between 100mV and 830mV. 14) Apply either +3.3V or +5V power to the board at the J7 (VCC) and J8 (GND) test points. Set the current limit to 300mA. 15) While monitoring the voltage on TP19, adjust R11 until the desired DC bias current is obtained. Turning the R11 potentiometer screw clockwise increases the DC bias current. 16) While monitoring the J5 SMA connector output on the oscilloscope, adjust R4 (R MOD ) until the desired modulation current is obtained. Turning the R4 potentiometer screw clockwise increases the modulation current. Evaluates: MAX3286/MAX3296 Electrical Quick Start with Bias-Current Feedback (VCSEL) 1) Configure the board to directly regulate the DC bias current. Set up the following shunts: SHUNT SP3 SP4 SP5 SP6 SP7 SP8 SP9 SP10 SP11 STATUS Closed Open Closed Closed Open Open Closed Closed Open Refer to the MAX3286/MAX3296 Common-Cathode Laser Without Photodiode application circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet. 2) Make sure nothing is installed in the laser socket (Figure 1). 3) Confirm that R24 is installed. 4) Make sure L8 is not installed. 5) Confirm that C12 is open. Without a laser installed, no compensation network is necessary. 6) Set potentiometer R11 to midscale by turning the screw counterclockwise until a faint click is felt, then clockwise for 15 full revolutions (30 full revolutions in the 0 to 200 range of the multiturn potentiometer). This sets the regulation point for the laser bias current to 0.25V / 100 = 2.5mA. 7) Set potentiometer R4 (RMOD) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 50k range of the multiturn potentiometer). This minimizes the modulation current. 8) Set potentiometer R3 (RTC) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 100k range of the multiturn potentiometer). This minimizes the tempco of the modulation current. Emulating a Photodiode During Electrical Evaluation When evaluating the MAX3286/MAX3296 without a laser (see Electrical Quick Start sections), the MAX3286/MAX3296 DC bias circuitry operates using a photodiode emulator circuit. When shunts SP6 and SP7 are shorted, U2 (MAX4322), Q2 (FMMT491A), and R30 form a current-controlled current source that emulates the behavior of the photodiode in the laser assembly. R22 takes the place of the laser diode, and the photodiode emulator circuitry sinks a current from the collector of Q2 equal to 3% of the current through R22. This simulates the behavior of a laser diode and photodiode assembly where a fraction of the laser light reflects onto the photodiode, which then outputs a small current proportional to the light emitted. _______________________________________________________________________________________ 3 MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3286/MAX3296 _________________Optical Quick Start Optical Quick Start with Photodiode Feedback 1) Configure the board so that it will servo the laser bias current, achieving a fixed photodiode current. Set up the following shunts: SHUNT SP3 SP4 SP5 SP6 SP7 SP8 SP9 SP10 SP11 STATUS Open Closed Closed Open Open Closed Open Open Closed 10) Place jumpers across JU2 (EN), JU3 (EN), and JU4 (PORDLY). 11) If you intend to power the board from a +5V supply, place a jumper across JU1 (LV). Do not apply power yet. 12) Make sure there is no jumper on JU5 (FLTDLY). 13) Attach differential sources to SMA connectors J1 and J2. Each source should have a peak-to-peak amplitude between 100mV and 830mV. 14) Apply either +3.3V or +5V power to the board at the J7 (VCC) and J8 (GND) test points. 15) While monitoring the laser output, adjust R5 (RSET) until the desired laser bias current is obtained. Turning the R5 potentiometer screw clockwise increases the laser bias current. 16) While monitoring the laser output, adjust R4 (RMOD) until the desired laser modulation current is obtained. Turning the R4 potentiometer screw clockwise increases the laser modulation current. 17) Look at the "eye" output on the oscilloscope. Laser overshoot and ringing can be improved by appropriate selection of R13 and C12, as described in the Designing the Laser-Compensation Filter Network section of the MAX3286-MAX3289/MAX3296- MAX3299 data sheet. Refer to the MAX3286/MAX3296 Common-Cathode Laser with Photodiode applications circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet. 2) Remove R24. 3) Install L8. 4) Connect a laser to the board (Figure 1). 5) Set potentiometer R5 (RSET) to midscale by turning the screw counterclockwise until a faint click is felt, then clockwise for 15 full revolutions (30 full revolutions in the 0 to 10k range of the multiturn potentiometer). This sets the regulation point for the photodiode current to (2.65V - 1.7V) / 5k = 190A. 6) Set potentiometer R4 (RMOD) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 50k range of the multiturn potentiometer). This minimizes the modulation current (AC drive applied to laser). 7) Set potentiometer R3 (RTC) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 100k range of the multiturn potentiometer). This minimizes the tempco of the modulation current. 8) Set potentiometer R11 to 30 of resistance by turning the screw clockwise until a faint click is felt, then counterclockwise five turns. 9) Attach a 50 SMA terminator to J5 to match the laser loading. 4 Optical Quick Start with Bias-Current Feedback (VCSELs) 1) Configure the board to directly regulate the laser bias current. Set up the following shunts: SHUNT SP3 SP4 SP5 SP6 SP7 SP8 SP9 SP10 SP11 STATUS Closed Open Closed Open Open Open Closed Closed Open Refer to the MAX3286/MAX3296 Common-Cathode Laser Without Photodiode application circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet. 2) Remove R24. 3) Install L8. _______________________________________________________________________________________ MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit 4) Connect a laser to the board (Figure 1). 5) Set potentiometer R11 to midscale by turning the screw counterclockwise until a faint click is felt, then clockwise for 15 full revolutions (30 full revolutions in the 0 to 200 range of the multiturn potentiometer). This sets the regulation point for the laser bias current to 0.25V / 100 = 2.5mA. 6) Set potentiometer R4 (RMOD) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 50k range of the multiturn potentiometer). This minimizes the modulation current. 7) Set potentiometer R3 (RTC) to maximum resistance by turning the screw counterclockwise until a faint click is felt (30 full revolutions in the 0 to 100k range of the multiturn potentiometer). This minimizes the tempco of the modulation current. 8) Attach a 50 SMA terminator to J5 to match the laser loading. 9) Place jumpers across JU2 (EN), JU3 (EN), and JU4 (PORDLY). Section continues on page 8. S M A 2 Evaluates: MAX3286/MAX3296 1 4 1, 3 = GROUND 2 = LASER-DIODE ANODE 4 = PHOTODIODE CATHODE (LASER-DIODE CATHODE/PHOTODIODE ANODE) 3 MAX3286 MAX3296 Figure 1. Optical Connection Diagram Table 1. Adjustment and Control Descriptions COMPONENT D3 JU1 JU2 JU3 JU4 JU5 NAME FAULT LV EN EN PORDLY FLTDLY FUNCTION The LED shines red when a fault has occurred. The fault condition can be cleared by removing, then reinstalling, jumpers at JU2 or JU3. Placing a jumper on JU1 connects the LV pin to ground and programs the power-on reset circuit for +4.5V to +5.5V operation. Placing a jumper on JU2 ties the EN pin to VCC. When JU2 is not installed, the EN pin is pulled low by its internal pull-down. Placing a jumper on JU3 ties the EN pin to ground. When JU3 is not installed, the EN pin is pulled high by its internal pull-up. Placing a jumper on JU4 connects the PORDLY pin to a 0.01F capacitor (C5). Leaving JU4 open floats the PORDLY pin and minimizes the power-on reset time. Placing a jumper on JU5 disables the laser-driver safety features. Potentiometer R3, in conjunction with potentiometer R4 (RMOD), sets the tempco of the laser modulation current. Turn the potentiometer screw counterclockwise to increase the resistance. The tempco decreases when the potentiometer screw is turned counterclockwise. Potentiometer R4, in conjunction with potentiometer R3 (RTC), sets the peak-to-peak amplitude of the laser modulation current. Turn the potentiometer screw counterclockwise to increase the resistance. The laser modulation-current amplitude decreases when the potentiometer screw is turned counterclockwise. Potentiometer R5 adjusts the desired laser DC-current bias point. Potentiometer R5 sets the resistance from MD to ground, and MD regulates to 1.7V. Turn the potentiometer screw clockwise to decrease the resistance. The total range is 0 to 100k. The laser average power increases when the potentiometer screw is turned clockwise. R11 adjusts the amount of degeneration in the bias transistor when using a photodiode. When directly sensing bias current, R11 sets the regulation point. R3 RTC R4 RMOD R5 RSET R11 -- _______________________________________________________________________________________ 5 Evaluates: MAX3286/MAX3296 TC VCC VCC GND VCC OUT- VCC Q1 VCC SP3 R11 200 TP3 FAULT TP1 POR A C RED LED MODSET R25 511 FAULT SP5 VCC U1 MAX3296 SP4 VCC TP15 R9 1k R10 5.1k SP9 SP8 OUT+ FLTDLY LV VCC IN+ IN- GND REF C5 0.01F 9 10 11 12 13 14 15 16 N.C. MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit Figure 2. MAX3296 SW EV Kit Schematic R23 0 VCC C14 0.01F L8 1 L1 R13 24.9 TP20 SP6 2 1 3 D1 4 L2 VCC TP10 MODSET C2 0.01F TP9 TC TP4 32 31 30 29 28 27 26 25 C11 0.1F Q4 FMMT591A R4 50k RMOD C13 0.01F R24 24.9 C12 OPEN 2 R12 0 C25 0.01F SP7 Q2 FMMT491A E TP19 C B1 MAX4322 U2 3 JU3 EN 4 1 FAULT 2 N.C. 3 FAULT 4 POR 5 GND 6 EN 7 EN 8 PORDLY BIASDRV 24 23 SHDNDRV 22 GND 21 MON 20 MD 19 N.C. 18 POL 17 POL R30 1k R22 36 JU5 FLTDLY SP11 VCC TP14 VCC C23 10F C26 0.01F J1 J2 C1 0.01F C3 0.01F C4 0.01F R2 115 1% R5 10k RSET SP10 C22 0.01F JU1 LV 6 J5 R20 49.9 R3 100k RTC D3 VCC EN JU2 JU4 PORDLY VCC J7 L4 J8 _______________________________________________________________________________________ GND MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3286/MAX3296 1.0" 1.0" Figure 3. MAX3296 SW EV Kit Component Placement Guide--Top Silkscreen Figure 4. MAX3296 SW EV Kit PC Board Layout--Component Side 1.0" 1.0" Figure 5. MAX3296 SW EV Kit PC Board Layout--Ground Plane Figure 6. MAX3296 SW EV Kit PC Board Layout--Power Plane _______________________________________________________________________________________ 7 MAX3296 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3286/MAX3296 10) If you intend to power the board from a +5V supply, place a jumper across JU1 (LV). Do not apply power yet. 11) Make sure there is no jumper on JU5 (FLTDLY). 12) Attach differential sources to SMA connectors J1 and J2. Each source should have a peak-to-peak amplitude between 100mV and 830mV. 13) Apply either +3.3V or +5V power to the board at the J7 (VCC) and J8 (GND) test points. Set the current limit to 300mA. 14) While monitoring the laser output, adjust R11 until the desired DC bias current is obtained. Turning the R11 potentiometer screw clockwise increases the DC bias current. 15) While monitoring the laser output, adjust R4 (R MOD ) until the desired modulation current is obtained. Turning the R4 potentiometer screw clockwise increases the modulation current. 16) Look at the "eye" output on the oscilloscope. Laser overshoot and ringing can be improved by appropriate selection of R13 and C12 as described in the Designing the Laser-Compensation Filter Network section of the MAX3286-MAX3289/ MAX3296- MAX3299 data sheet. 1.0" Figure 7. MAX3296 SW EV Kit PC Board Layout--Solder Side Maxim makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Maxim assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters can and do vary in different applications. All operating parameters, including "typicals" must be validated for each customer application by customer's technical experts. Maxim products are not designed, intended or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Maxim product could create a situation where personal injury or death may occur. 8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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