19-3116; Rev 2; 9/10 3.2Gbps, Low-Power, Compact, SFP Laser Driver Features Fully Compatible with SFP and SFF-8472 Specifications The MAX3736 is a compact, +3.3V multirate laser driver for SFP/SFF applications up to 3.2Gbps. The device accepts differential data and provides bias and modulation currents for driving a laser. DC-coupling to the laser allows for multirate applications, and reduces the number of external components. The wide 5mA to 60mA (85mA AC-coupled) modulation current range and 1mA to 100mA bias current make the MAX3736 ideal for driving FP/DFB laser diodes in fiberoptic modules. The laser current setting can be controlled by a current DAC, a voltage DAC, or a resistor. Very low power dissipation, small package size, and reduced component count, make this part an ideal solution for SFP-module applications. The MAX3736 is available in a small 3mm x 3mm, 16-pin thin QFN package. It operates over a -40C to +85C temperature range. Programmable Modulation Current from 5mA to 60mA (DC-Coupled) Programmable Modulation Current from 5mA to 85mA (AC-Coupled) Programmable Bias Current from 1mA to 100mA 56ps Edge Transition Times 22mA (typ) Power-Supply Current Multirate Operation Up to 3.2Gbps On-Chip Pullup Resistor for DIS 16-Pin, 3mm x 3mm Thin QFN Package Ordering Information PART Applications Gigabit Ethernet SFP/SFF Transceiver Modules TEMP RANGE PIN-PACKAGE MAX3736ETE -40C to +85C 16 Thin QFN-EP* MAX3736ETE+ -40C to +85C 16 Thin QFN-EP* 1G/2G Fibre-Channel SFP/SFF Transceiver Modules +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad. Multirate OC-3 to OC-48 FEC SFP/SFF Transceiver Modules Pin Configuration appears at end of data sheet. 10G Ethernet LX-4 Modules Typical Application Circuit HOST BOARD SFP OPTICAL TRANSMITTER +3.3V SUPPLY FILTER HOST FILTER 15 56 0.01F VCC VCC_RX 0.1F OUT- 8.2pF IN+ 50 10 0.1F TX_DISABLE MOD-DEF1 MOD-DEF2 BIASSET DIS MODSET MAX3736 INBC_MON 50 OUT+ BIAS GND SERDES FERRITE BEAD LASER CONTROLLER ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com. 1 MAX3736 General Description MAX3736 3.2Gbps, Low-Power, Compact, SFP Laser Driver ABSOLUTE MAXIMUM RATINGS Operating Junction Temperature Range ..........-55C to +150C Storage Temperature Range .............................-55C to +150C Die Attach Temperature ..................................................+400C Lead Temperature (soldering, 10s) .................................+300C Soldering Temperature (reflow) Lead(Pb)-free...............................................................+260C Containing lead(Pb) .....................................................+240C Power-Supply Voltage VCC ..................................-0.5V to +6.0V Voltage at IN+, IN-, DIS..........................-0.5V to (VCC + 0.5V) Voltage at BC_MON, MODSET, BIASSET .............-0.5V to +3.0V Voltage at OUT+, OUT-.........................+0.5V to (VCC + 1.5V) Voltage at BIAS ....................................+0.5V to (VCC + 0.5V) Current into BIAS, OUT+, OUT- ......................-20mA to +150mA Current into IN+, IN-....................................-20mA to +20mA Continuous Power Dissipation (TA = +85C) 16-Pin Thin QFN (derate 25mW/C above +85C) .............2W Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS (VCC = +2.97V to +3.63V, TA = -40C to +85C. Typical values are at VCC = +3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Power-Supply Current SYMBOL CONDITIONS ICC Excludes the laser bias and modulation currents (Note 2) VID VID = VIN+ - VIN-, Figure 1 MIN TYP MAX UNITS 22 35 mA 2.4 VP-P I/O SPECIFICATIONS Differential Input Voltage Common-Mode Input Voltage 0.2 0.6 VCC VINCM V Differential Input Resistance RIN 85 100 115 DIS Input Pullup Resistance RPULL 4.7 7.2 10.0 k VDIS = VCC DIS Input Current 15 VDIS = VGND, VCC = 3.3V, RPULL = 7.4k DIS Input High Voltage VIH DIS Input Low Voltage VIL -450 2.0 A V 0.8 V 100 mA 100 A BIAS GENERATOR Bias Current Range Bias Off-Current BIASSET Current Gain IBIAS IBIASOFF GBIAS Current into BIAS pin 1 Current into BIAS pin, DIS asserted high (Note 3) 5mA IBIAS 10mA 70 85 95 10mA IBIAS 100mA 79 85 91 A/A BIASSET Current Gain Stability 10mA IBIAS 100mA (Note 4) -4.4 +4 % BIASSET Current Gain Linearity 10mA IBIAS 100mA (Note 5) -2.3 +2.3 % Bias Overshoot During SFP module hot plugging; see Figure 3 (Notes 5, 6) 10 % Bias-Current Monitor Gain Bias-Current Monitor Gain Stability (Notes 4, 5) 2 (Note 5) 13.7 mA/A |4| 1mA IBIAS 5mA 5mA IBIAS 10mA -7 10mA IBIAS 100mA -5 |2.8| |2.4| _______________________________________________________________________________________ +7 +5 % 3.2Gbps, Low-Power, Compact, SFP Laser Driver (VCC = +2.97V to +3.63V, TA = -40C to +85C. Typical values are at VCC = +3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25C, unless otherwise noted.) (Note 1) PARAMETER Modulation Current Range SYMBOL IMOD CONDITIONS MIN Current into OUT+, RL = 15, VOUT+ and VOUT- 0.6V (DC-coupled) 5 Current into OUT+, RL = 15, VOUT+ and VOUT- 2.0V (AC-coupled) 5 TYP MAX UNITS 60 mAP-P 85 MODULATOR Modulation Current Gain GMOD (Note 3) 5mA IMOD 10mA 70 85 95 10mA IMOD 85mA 79 85 91 A/A Modulation Current Gain Stability 10mA IMOD 85mA (Notes 4, 5) -4.4 +4 % Modulation Current Gain Linearity 10mA IMOD 85mA (Note 5) -3.3 +3.3 % IBIASSET = 0.15mA; IMODSET = 0.7mA Bias Current Gain and Modulation Current Gain Matching (Notes 5, 7) Modulation OFF Current IMODOFF 2.3 IBIASSET = IMODSET = 0.15mA 0.1 1.4 IBIASSET = IMODSET = 0.4mA 0.1 1 IBIASSET = IMODSET = 0.6mA 0.1 1 IBIASSET = IMODSET = 0.9mA 0.1 DIS asserted high % 1 100 A Rise Time tR 20% to 80%; 10mA IMOD 60mA (Note 5) 48 80 ps Fall Time tF 80% to 20%; 10mA IMOD 60mA (Note 5) 58 80 ps 10mA IMOD 60mA; 2.67Gbps; 223-1 PRBS 16 38 10mA IMOD 60mA; 3.2Gbps; K28.5 pattern 17 38 10mA IMOD 60mA; 155Mbps; 223-1 PRBS 30 10mA IMOD 60mA; 3.2Gbps; K28.5; TA = +100C 6.3 10mA IMOD 60mA (Note 5) 0.6 Deterministic Jitter (Notes 5, 8) Random Jitter psP-P ps 1 psRMS Note 1: Specifications at -40C are guaranteed by design and characterization. Note 2: Maximum value is specified at IMOD = 60mA and IBIAS = 100mA. BC_MON connected to VCC. Note 3: Modulation current gain, GMOD, is defined as GMOD = IMOD / IMODSET. Bias current gain, GBIAS, is defined as GBIAS = IBIAS / IBIASSET. The nominal gain is measured at VCC = +3.3V and TA = +25C. Note 4: Gain stability is defined as [(Gain) - (Nom_Gain)] / (Nom_Gain) over the listed current range, temperature, and supply variation. Nominal gain is measured at VCC = +3.3V, TA = +25C. The voltage at the BC_MON pin must not exceed 1.39V. Note 5: Guaranteed by design and characterization; see Figure 2. Note 6: VCC turn-on time must be less than 0.8s, DC-coupled interface. Note 7: The gain matching is defined as ABS [(GMOD/GBIAS - GMODNOM/GBIASNOM)/(GMODNOM/GBIASNOM)] over the specified temperature and voltage supply range. Note 8: For supply noise tolerance, noise is added to the supply (100mVP-P) up to 2MHz; see Figure 3. _______________________________________________________________________________________ 3 MAX3736 ELECTRICAL CHARACTERISTICS (continued) MAX3736 3.2Gbps, Low-Power, Compact, SFP Laser Driver VOLTAGE VIN+ VCC VCC 100mV MIN 1200mV MAX VIN- 25 26 OUT- (VIN+) - (VIN-) 30 200mVP-P MIN 2400mVP-P MAX MAX3736 CURRENT IOUT+ 1.1pF OSCILLOSCOPE OUT+ IOUT+ IMOD Figure 1. Definition of Single-Ended Input Voltage Range SOURCE NOISE VOLTAGE SUPPLY Figure 2. Output Termination for Characterization HOST BOARD FILTER DEFINED BY SFP MSA MODULE TO LASER DRIVER VCC OPTIONAL 1H 0.1F 50 130 10F OPTIONAL 0.1F Figure 3. Supply Filter Typical Operating Characteristics (Typical values are at VCC = 3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25C, unless otherwise noted.) 1870MHz FILTER 223 - 1 PRBS C4 919ps/div 4 58ps/div 58ps/div _______________________________________________________________________________________ MAX3736 toc03 ER = 8.2dB, OC-48 FILTER 231 - 1 PRBS, 1310 FP LASER MAX3736 toc02 117 MHz FILTER, 231 - 1 PRBS 1310nm FP LASER ELECTRICAL EYE (2.488Gbps) OPTICAL EYE (2.488Gbps) MAX3736 toc01 OPTICAL EYE (155Mbps) 3.2Gbps, Low-Power, Compact, SFP Laser Driver BIAS CURRENT MONITOR GAIN vs. TEMPERATURE 70 80 MAX3736 toc06 EXCLUDES IBIAS AND IMOD 18 70 60 50 40 IMOD (mAP-P) GAIN (mA/A) 60 16 14 30 50 40 30 20 12 20 10 10 10 -15 10 35 60 85 0 -40 -15 10 35 60 85 1 RMODSET (k) EDGE TRANSITION TIME vs. MODULATION AMPLITUDE BIAS CURRENT vs. BIAS RESISTANCE 80 70 60 50 40 30 80 MAX3736 toc09 90 70 EDGE TRANSITION TIME (ps) 100 100 10 TEMPERATURE (C) TEMPERATURE (C) MAX3736 toc08 -40 IBIAS (mA) SUPPLY CURRENT (mA) 20 MAX3736 toc05 80 MODULATION CURRENT vs. MODSET RESISTANCE (ZL = 15) MAX3736 toc07 SUPPLY CURRENT vs. TEMPERATURE FALL TIME 60 50 40 RISE TIME 30 20 20 10 0 10 1 10 RBIASSET (k) 100 10 20 30 40 50 60 IMOD (mA) _______________________________________________________________________________________ 5 MAX3736 Typical Operating Characteristics (continued) (Typical values are at VCC = 3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25C, unless otherwise noted.) Typical Operating Characteristics (continued) (Typical values are at VCC = 3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25C, unless otherwise noted.) DETERMINISTIC JITTER vs. MODULATION CURRENT MAX3736 toc11 2.7Gbps 223-1 PRBS 50 DIFFERENTIAL S11 vs. FREQUENCY 0 MAX3736 toc10 60 -5 40 -10 IS11I (dB) DJ (psP-P) MAX3736 3.2Gbps, Low-Power, Compact, SFP Laser Driver 30 -15 20 -20 10 -25 0 -30 20 10 30 40 50 60 0 IMOD (mAP-P) 2 4 6 8 10 FREQUENCY (GHz) Pin Description 6 PIN NAME 1, 4, 9, 12, 15 FUNCTION VCC 2 IN+ Noninverted Data Input 3 IN- Inverted Data Input 5 BIASSET A current DAC, a voltage DAC, or a resistor, connected from this pin to ground, sets the desired bias current for the laser (see the Programming the Laser Bias Current section). 6 MODSET A current DAC, a voltage DAC, or a resistor, connected from this pin to ground, sets the desired bias current for the laser (see the Programming the Laser Modulation Current section). 7 BC_MON Bias Current Monitor Output. Current out of this pin develops a ground-referenced voltage across an external resistor that is proportional to the bias current. +3.3V Supply Voltage. All pins must be connected to VCC. 8 BIAS 10 OUT+ Laser Bias Current Output Noninverted Modulation Current Output. IMOD flows into this pin when input data is high. 11 OUT- Inverted Modulation Current Output. IMOD flows into this pin when input data is low. 13, 14 GND Ground 16 DIS Transmitter Disable, TTL. Laser output is disabled when DIS is asserted high or left unconnected. The laser output is enabled when this pin is asserted low. -- EP Exposed Pad. Must be soldered to the circuit board ground for proper thermal and electrical performance (see the Exposed-Pad Package section). _______________________________________________________________________________________ 3.2Gbps, Low-Power, Compact, SFP Laser Driver MAX3736 DIS VCC VCC 82pF 16k 7.2k OUT+ 24k 50 OUT- 50 IN+ IN- VCC VCC BIAS VCC x1 x85 x85 BC_MON 1.2V 1.2V MAX3736 BIASSET MODSET Figure 4. Functional Diagram Detailed Description The MAX3736 laser driver consists of three operational blocks: a bias current generator, a modulation current generator, and a high-speed modulation path. The laser-biasing block includes a monitor output for biassensing purposes. Both the bias and modulation generating blocks are enabled and disabled by the DIS pin. The high-speed modulation path provides a 100 differential input resistance. Bias Current Monitor The MAX3736 features a bias current monitor (BC_MON). This monitor is realized by mirroring a fraction of the bias current and developing a voltage across an external resistor connected to ground. For example, connecting a 100 resistor to ground gives the following relationship: VBC_MON = (IBIAS / 73) x 100. For compliance, the voltage on BC_MON must be kept below 1.39V. Bias Current Generator Modulation Current Generator To maintain constant average optical power, the MAX3736 is designed to interface to a laser controller IC. The laser controller IC controls the MAX3736, and maintains a constant laser power using an automatic power-control (APC) circuit. A back-facet photodiode, mounted in the laser package, is used to convert the optical power into a photocurrent. The laser controller IC adjusts the laser bias current so the monitor photodiode's current matches the level programmed by the user. It does this by adjusting the current sourced by the MAX3736's BIASSET pin. The MAX3736 reacts by increasing or decreasing the laser current at BIAS. The laser's modulation amplitude can be controlled by placing a resistor from MODSET to ground. To set the modulation amplitude, see the I MOD vs. R MODSET graph in the Typical Operating Characteristics. A more advanced control scheme employs the use of a laser controller IC to control modulation current to stabilize the extinction ratio. For more information on controlling the extinction ratio, refer to Application Note 1092: HFAN-02.3.1: Maintaining Average Power and Extinction Ratio, Part 1, Slope Efficiency and Threshold Current. _______________________________________________________________________________________ 7 MAX3736 3.2Gbps, Low-Power, Compact, SFP Laser Driver High-Speed Modulation Driver The output stage is composed of a high-speed differential pair and a programmable modulation current source. The MAX3736 is optimized for driving a 15 load; the minimum instantaneous voltage required at OUT+ is 0.6V. Modulation current swings up to 60mA are possible. To interface with the laser diode, a damping resistor (RD) is required for impedance matching. The combined resistance of the series damping resistor and the equivalent series resistance of the laser diode should equal 15. To reduce optical output aberrations and dutycycle distortion caused by laser diode parasitic inductance, an RC shunt network might be necessary. Refer to Application Note 274: HFAN-02.0: Interfacing Maxim Laser Drivers with Laser Diodes for more information. At high data rates, e.g., 2.5Gbps, any capacitive load at the cathode of a laser diode degrades optical output performance. Because the BIAS output is directly connected to the laser cathode, minimize the parasitic capacitance associated with the pin by using an inductor to isolate the BIAS pin parasitics from the laser cathode. In the absence of input data, the modulation current switches to OUT-, squelching the transceiver output. Disable The DIS pin disables the modulation and bias current. The typical enable time is 2s for bias current and 1s for modulation current. The typical disable time is 200ns for bias current and 250s for modulation current. The DIS pin has a 7.4k internal pullup resistor. Design Procedure Programming the Modulation Current There are three methods for setting the modulation current on the MAX3736 laser driver. The current can be set by using a current DAC, a voltage DAC in series with a resistor, or by using a resistor connected to GND. To program the laser modulation current using a current DAC, attach the DAC to the MODSET pin and set the current using the following equation: To program the laser modulation current using a voltage DAC, attach the DAC to the MODSET pin through a series resistor, RSERIES, and set the current using the following equation: IMOD = 1.2V - VDAC x 85 RSERIES To program the laser modulation current using a resistor, place the resistor from MODSET to ground. IMOD current can be calculated by the following equation: IMOD = 1.2V x 85 RMODSET Programming the Bias Current There are three methods for setting the bias current on the MAX3736 laser driver. The current can be set by using a current DAC, a voltage DAC in series with a resistor, or by using a resistor connected to GND. To program the laser bias current using a current DAC, attach the DAC to the BIASSET pin and set the current using the following equation: IBIAS = IBIASET x 85 To program the laser bias current using a voltage DAC, attach the DAC to the BIASSET pin through a series resistor, RSERIES, and set the current using the following equation: IBIAS = 1.2V - VDAC x 85 RSERIES To program the laser bias current using a resistor, place the resistor from BIASSET to ground. IBIAS current can be calculated by the following equation: IBIAS = 1.2V RBIASET x 85 IMOD = IMODSET x 85 8 _______________________________________________________________________________________ 3.2Gbps, Low-Power, Compact, SFP Laser Driver MAX3736 VCC VCC MAX3736 82pF PACKAGE 16k MAX3736 PACKAGE VCC 0.43nH IN+ OUT- 0.65nH 0.11pF 0.11pF 0.43nH 50 OUT+ 0.11pF VCC 50 IN0.11pF 0.65nH 24k Figure 5. Simplified Input Circuit Schematic Input Termination Requirements The MAX3736 data inputs are SFP MSA compliant. Onchip 100, differential input impedance is provided for optimal termination (Figure 5). Because of the on-chip biasing network, the MAX3736 inputs self-bias to the proper operating point to accommodate AC-coupling. Applications Information Data Input Logic Levels The MAX3736 is directly compatible with +3.3V reference CML. Either DC or AC-coupling can be used for CML referenced to +3.3V. For all other logic types, AC-coupling should be used. DC coupling to CML is fine, but it negates the squelching function on the modulation path. Modulation Currents Exceeding 60mA For applications requiring a modulation current greater than 60mA, headroom is insufficient for proper operation of the laser driver if the laser is DC-coupled. To avoid this problem, the MAX3736 modulation output can be AC-coupled to the cathode of a laser diode. An external pullup inductor is necessary to DC-bias the modulation output at VCC. Such a configuration isolates laser forward voltage from the output circuitry and allows the output at OUT+ to swing above and below the supply Figure 6. Simplified Output Circuit Schematic voltage (VCC). When AC-coupled, the MAX3736 modulation current can be programmed from 5mA to 85mA. Refer to Maxim Application Note HFAN 02.0: Interfacing Maxim's Laser Drivers to Laser Diodes for more information on AC-coupling laser drivers to laser diodes. Interface Models Figures 5 and 6 show simplified input and output circuits for the MAX3736 laser driver. Layout Considerations To minimize loss and crosstalk, keep the connections between the MAX3736 output and the laser as short as possible. Use good high-frequency layout techniques and multilayer boards with an uninterrupted ground plane to minimize EMI and crosstalk. Exposed-Pad Package The exposed pad on the 16-pin QFN provides a very low thermal resistance path for heat removal from the IC. The pad is also electrical ground on the MAX3736 and must be soldered to the circuit board ground for proper thermal and electrical performance. Refer to Application Note 862: HFAN-08.1: Thermal Considerations of QFN and Other Exposed-Paddle Packages for additional information. _______________________________________________________________________________________ 9 Chip Information Laser Safety and IEC 825 Using the MAX3736 laser driver alone does not ensure that a transmitter design is compliant with IEC 825. The entire transmitter circuit and component selections must be considered. Customers must determine the level of fault tolerance required by their application. Please recognize that Maxim products are not designed or authorized for use as components in systems intended for surgical implant into the body, for applications intended to support or sustain life, or for any other application where the failure of a Maxim product could create a situation where personal injury or death may occur. PROCESS: SiGe BiPOLAR Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. Note that a "+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status. PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND PATTERN NO. 16 TQFN-EP T1633-2 21-0136 90-0030 VCC 1 IN+ 2 VCC GND GND TOP VIEW DIS Pin Configuration 16 15 14 13 12 VCC 11 OUT- MAX3736 4 EP 9 5 6 7 8 BIAS VCC 10 OUT+ BC_MON 3 MODSET IN- BIASSET MAX3736 3.2Gbps, Low-Power, Compact, SFP Laser Driver VCC THIN QFN (3mm x 3mm) THE EXPOSED PAD MUST BE CONNECTED TO GROUND FOR PROPER THERMAL AND ELECTRICAL PERFORMANCE. 10 ______________________________________________________________________________________ 3.2Gbps, Low-Power, Compact, SFP Laser Driver REVISION NUMBER REVISION DATE 0 12/03 1 2 DESCRIPTION PAGES CHANGED Initial release -- 2/06 Added lead(Pb)-free part to the Ordering Information table 1 9/10 Removed the dice package from the Ordering Information table and the Electrical Characteristics table Note 1; removed the Wire-Bonding Die, Chip Topography/Pad Configuration, Chip Topography, and Bonding Coordinates sections and Table 1; added the soldering information for leaded and lead-free packages to the Absolute Maximum Ratings section; added the Package Information table 1, 2, 3, 9, 10, 11 Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 11 (c) 2010 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX3736 Revision History