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19-1961; Rev 0; 2/01
MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit
General Description
The MAX3287 shortwave or VCSEL evaluation kit (EV kit) is an assembled, surface-mount demonstration board that allows easy optical and electrical evaluation of the MAX3287/MAX3288 1.25Gbps laser drivers or the MAX3297/MAX3298 2.5Gbps laser drivers in the common-cathode configuration. Short-wavelength laser diodes (wavelength 980nm) and vertical cavity-surface emitting lasers (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. When used with the MAX3287/MAX3297, the laser bias current regulates to keep a constant photodiode current (for shortwave laser diodes). When used with the MAX3288/MAX3298, the laser bias current is directly sensed and held constant. This EV kit includes an extra blank circuit without components to demonstrate a small, tight layout optimized for optical evaluation. o Drives Common-Cathode Lasers o Includes Socket for Laser Insertion o Evaluates MAX3287 (installed) or MAX3288/97/98 o Adjustable DC Bias Current (MAX3288/98) o Adjustable Photodiode Current (MAX3287/97) o Adjustable Modulation Current o Adjustable Modulation-Current Tempco o Configured for Electrical Operation, No Laser Necessary o Extra-Small-Size Blank Circuit (for optical evaluation only)
Features
Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
Ordering Information
PART MAX3287EVKIT TEMP. RANGE 0C to +70C IC PACKAGE 16 TSSOP
Component List
DESIGNATION QTY C1-C4, C13, C14, C22, C40, C52 C11 C12 C23 D1 J1, J2 9 DESCRIPTION 0.01F 10%, 10V min, X7R ceramic capacitors (0402) 0.1F 10%, 10V min, X7R ceramic capacitor (0603) Open, user supplied (0402)* 10F 10%, 16V tantalum capacitor AVX TAJC106K016 Open, user supplied (laser diode and photodiode assembly; Figure 1) Test points Mouser 151-203 SMA connectors (edge mount) EFJohnson 142-0701-801 or Digi-Key J502-ND 2-pin header (0.1in centers) 3-pin header (0.1in centers) Ferrite beads Murata BLM11HA102SG R11 R12, R23 1 2 DESIGNATION QTY L3 L4 Q1 Q2 Q6 R2 0 2 R3 R4 R5 R9 R10 JU3 L1, L2 1 2 1 1 0 1 1 1 1 1 1 1 1 DESCRIPTION Ferrite bead (included but not installed) Murata BLM11HA102SG Ferrite bead Murata BLM11HA601SG Open Zetex FMMT591A Zetex FMMT491A 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% resistor (0402) 5.1k 5% resistor (0402) 200 variable resistor Bourns or Digi-Key 3296W-201-ND 0 resistors (0402)
1 0 1
J4, J5, J15 JU1
3 1
*See page 2 for note. ________________________________________________________________ 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.
MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
Component List (continued)
DESIGNATION QTY R13 R20 R24 R37 TP1, TP2, TP3, TP9, TP10 R38 U2, U3 U2, U3 U2, U3 U2, U3 U5 1 1 0 1 6 1 2 2 2 2 1 DESCRIPTION 24.9 1% resistor (0402)* 49.9 1% resistor (0402) 24.9 1% resistor (0402) 36 5% resistor (0603) Test points Mouser 151-203 1k 5% resistor (0402) MAX3287CUE (16-pin TSSOP-EP) MAX3288CUE (16-pin TSSOP-EP, included but not installed) MAX3297CUE (16-pin TSSOP-EP, included but not installed) MAX3298CUE (16-pin TSSOP-EP, included but not installed) MAX4322EUK (5-pin SOT23)
*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.
Electrical Quick Start
Electrical Quick Start with the MAX3287/MAX3297 and 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 SP1 SP2 SP3 SP4 SP5 SP6 SP7 SP8 STATUS Closed Closed Open Closed Closed Closed Open Open
Refer to the MAX3287/MAX3297 common-cathode laser with photodiode application circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet.
2
2) Make sure nothing is installed in the laser socket (Figure 1). 3) Confirm that R24 is installed. 4) Make sure L3 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 Q2 to (28 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 five turns. 10) Make sure there is no jumper on JU1 (FLTDLY). 11) Put a jumper between pins 1 and 2 of JU3 to provide power to the main circuit (instead of to the optimized layout circuit). 12) Attach a cable with 50 characteristic impedance between the J15 SMA output connector and the input of the oscilloscope. Make sure the oscilloscope input is 50 terminated. 13) Attach differential sources to SMA connectors J4 and J5. 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 J1 (VCC) and J2 (GND) test points. Set the current limit to 300mA. 15) While monitoring the voltage across R37 (TP3 to GND), adjust R5 (RSET) until the desired DC bias current is obtained. Turning the R5 potentiometer screw clockwise increases the DC bias current. 16) While monitoring the J15 SMA connector output on the oscilloscope, adjust R4 (R MODSET) until the desired modulation current is obtained. Turning the R4 potentiometer screw clockwise increases the modulation current.
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MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit
S M A
MAX3287 MAX3288 MAX3297 MAX3298
2
1
3
4
2 = LASER-DIODE ANODE 4 = PHOTODIODE CATHODE 1, 3 = GROUND (LASER-DIODE CATHODE/PHOTODIODE ANODE)
Figure 1. Optical Connection Diagram
Electrical Quick Start with the MAX3288/MAX3298 and Bias-Current Feedback (VCSEL)
1) Configure the board to directly regulate the DC bias current. Set up the following shunts:
SHUNT SP1 SP2 SP3 SP4 SP5 SP6 SP7 SP8 STATUS Open Closed Closed Open Closed Open Closed Closed
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. 9) Make sure there is no jumper on JU1 (FLTDLY). 10) Put a jumper between pins 1 and 2 of JU3 to provide power to the main circuit (instead of to the optimized layout circuit). 11) Attach a 50 characteristic impedance cable between the J15 SMA output connector and the input of the oscilloscope. Make sure the oscilloscope input is 50 terminated. 12) Attach differential sources to SMA connectors J4 and J5. 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 J1 (VCC) and J2 (GND) test points. Set the current limit to 300mA. 14) While monitoring the voltage between TP3 and GND, 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 J15 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.
Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
2 3) 4) 5) 6)
Refer to the MAX3288/MAX3298 common-cathode laser without photodiode application circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet. Make sure nothing is installed in the laser socket (Figure 1). Confirm that R24 is installed. Make sure L3 is not installed. Confirm that C12 is open. Without a laser installed, no compensation network is necessary. Set the R11 potentiometer to midscale by turning the screw counterclockwise until a faint click is felt,
Emulating a Photodiode During Electrical Evaluation
When evaluating the MAX3287/MAX3297 without a laser (see Electrical Quick Start with the MAX3287/ MAX3297 and Simulated Photodiode Feedback), the MAX3287/MAX3297 DC bias circuitry operates using a photodiode emulator circuit. When shunts SP1 and SP2 are shorted, U5 (MAX4322), Q6 (FMMT491A), and R38 form a current-controlled current source that emulates the behavior of the photodiode in the laser assembly. R37 takes the place of the laser diode, and the photodiode emulator circuitry sinks a current from the collector of Q6 equal to 3% of the current through R37. This sim3
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MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
ulates 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. 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 J15 to match the laser loading. 10) Make sure there is no jumper on JU1 (FLTDLY). 11) Put a jumper between pins 1 and 2 of JU3 to provide power to the main circuit (instead of to the optimized layout circuit). 12) Attach differential sources to SMA connectors J4 and J5. 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 J1 (VCC) and J2 (GND) test points. 14) 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. 15) 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. 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.
Optical Quick Start
Optical Quick Start with the MAX3287/MAX3297 and 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 SP1 SP2 SP3 SP4 SP5 SP6 SP7 SP8 STATUS Open Open Open Closed Closed Closed Open Open
Refer to the MAX3287/MAX3297 common-cathode laser with photodiode applications circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet. 2) Remove R24. 3) Install L3. 4) Connect a laser to the board (Figure 1). 5) Set the R5 (R SET) potentiometer 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.
4
Optical Quick Start with the MAX3288/ MAX3298 and Bias-Current Feedback (VCSELs)
1) Configure the board to directly regulate the laser bias current. Set up the following shunts:
SHUNT SP1 SP2 SP3 SP4 SP5 SP6 SP7 SP8 STATUS Open Open Closed Open Closed Open Closed Closed
Refer to the MAX3288/MAX3298 common-cathode laser without photodiode applications circuit in the MAX3286-MAX3289/MAX3296-MAX3299 data sheet.
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MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit
2) Remove R24 3) Install L3. 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 J15 to match the laser loading. 9) Make sure there is no jumper on JU1 (FLTDLY). 10) Put a jumper between pins 1 and 2 of JU3 to provide power to the main circuit (instead of to the optimized layout circuit). 11) Attach differential sources to SMA connectors J4 and J5. Each source should have a peak-to-peak amplitude between 100mV and 830mV. 12) Apply either +3.3V or +5V power to the board at the J1 (VCC) and J2 (GND) test points. Set the current limit to 300mA. 13) 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. 14) 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. 15) 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.
Detailed Description
Evaluating the MAX3288/MAX3297/MAX3298
The MAX3287 EV kit ships with the MAX3287 installed in the circuit, but the board can be modified to accommodate the MAX3288, MAX3297, or MAX3298. The MAX3287 comes in an exposed-paddle package. The exposed paddle is an area of exposed metal leadframe underneath the 16-pin package that is soldered to a copper thermal pad. To evaluate the MAX3288/ MAX3297/MAX3298, first follow these steps to remove the MAX3287 from the board: 1) Use a solder wick to remove as much solder as possible from the leads on the MAX3287. 2) Using a small metal pick, heat each lead, and gently lift it from its pad (being careful not to damage the underlying trace). 3) Flip the board over and notice that there is a hole underneath the exposed paddle of the MAX3287 in the middle of the thermal pad. Place the tip of a soldering iron into the hole in the thermal pad; the MAX3287 should fall away from the board. 4) Use the solder wick to remove any residual solder around the thermal pad. Once the MAX3287 has been removed, any of the other three ICs may be mounted on the board.
Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
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5
Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
OUTR20 49.9 VCC C40 0.01F C12 OPEN C13 0.01F VCC 3 1 Q2 2 1 3 VCC R11 200 RMON D1 3 SP1 Q6 R9 R10 1k 5.1k SP8 SP4
MAX4322
J1 2 JU3 C2 0.01F SP5 VCC SP3 Q1 2 TP9 TP2 C11 0.1F 1
L4
3
1 GND TC 16 15 2 FLTDLY MODSET 14 3 VCC VCC 4 IN+ OUT- 13 12 5 OUT+ IN11 6 VCC GND 10 7 BIASDRV REF 9 SHDNDRV
8
MD
L5
VCC2 VCC2 C6 0.01F R25 OPEN R22 OPEN C27 0.1F
C8 0.01F C17 0.01F R27 24.9 VCC2
L8
MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit
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L1 C14 0.01F R12 0 L3 R24 24.9 TP10 VCC2 R4 50k RMOD L2 SP2 R13 24.9 C52 0.01F VCC R3 100k RTC
C32 0.01F VCC2 C31 0.01F C30 0.01F J7 J6 R30 115
16 1 GND TC 15 2 FLTDLY MODSET 14 3 VCC VCC 4 IN+ OUT- 13 12 5 OUT+ IN11 6 VCC GND 10 7 BIASDRV REF 8 MD SHDNDRV 9
Figure 2. MAX3287 EV Kit Schematic
R23 0
6
U2 MAX3287
1 TP3 FLTDLY JU1 SP7 TP1 VCC C1 0.01F C3 0.01F J4 J5 C4 0.01F RSET R5 10k R2 115 1% SP6 R38 1k C22 0.01F
U5
J15
VCC1
J2
C23 10F
GND
4
R37 36
VCC2 VCC2
C25 OPEN
R42 0 C28 0.01F R1 36 Q4
R26 24.9
U3
L9
MAX3287
D3
R29 OPEN
C29 0.01F
NOTE: THE CIRCUIT ENCLOSED IN DOTTED LINES IS A BLANK, UNSTUFFED LAYOUT ON THE MAX3287 EV KIT BOARD.
MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
Table 1. Adjustment and Control Descriptions
COMPONENT JU1 R3 NAME FLTDLY RTC FUNCTION Placing a jumper on JU1 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 turns 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 turns 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 10k. The laser average power increases when the potentiometer screw turns 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.
R4
RMOD
R5
RSET
R11
RMOD
1.0"
1.0"
Figure 3. MAX3287 EV Kit Component Placement Guide
Figure 4. MAX3287 EV Kit PC Board Layout--Component Side
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7
MAX3287 Shortwave or VCSEL (Common Cathode) Evaluation Kit Evaluates: MAX3287/MAX3288/MAX3297/MAX3298
1.0"
1.0"
Figure 5. MAX3287 EV Kit PC Board Layout--Solder Side
Figure 6. MAX3287 EV Kit PC Board Layout--Ground Plane
1.0"
Figure 7. MAX3287 EV Kit PC Board Layout--Power Plane
Maxim makes no warranty, presentation 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) 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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