TOP VIEW FAULT FAULT POR GND PORDLY. Maxim Integrated Products 1

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1 ; Rev 3; 7/02 General Description The / series of products are highspeed laser drivers for fiber optic LAN transmitters, optimized for Gigabit Ethernet applications. Each device contains a bias generator, laser modulator, and comprehensive safety features. Automatic power control (APC) adjusts the laser bias current to maintain average optical power at a constant level, regardless of changes in temperature or laser properties. For lasers without a monitor photodiode, these products offer a constant-current mode. The circuit can be configured for use with conventional shortwave (780nm to 850nm) or longwave (1300nm) laser diodes, as well as verticalcavity surface-emitting lasers (VCSELs). The series ( MAX3289) is optimized for operation at 1.25Gbps, and the series ( MAX3299) is optimized for 2.5Gbps operation. Each device can switch 30mA of laser modulation current at the specified data rate. Adjustable temperature compensation is provided to keep the optical extinction ratio within specifications over the operating temperature range. This series of devices is optimized to drive lasers packaged in low-cost TO-46 headers. Deterministic jitter (DJ) for the is typically 22ps, allowing a 72% margin to Gigabit Ethernet DJ specifications. These laser drivers provide extensive safety features to guarantee single-point fault tolerance. Safety features include dual enable inputs, dual shutdown circuits, and a laser-power monitor. The safety circuit detects faults that could cause dangerous light output levels. A programmable power-on reset pulse initializes the laser driver at startup. The / are available in a compact, 5mm 5mm, 28-pin QFN package; a 5mm 5mm, 32-pin TQFP package; or in die form. The MAX3287/MAX3288/ MAX3289 and MAX3297/MAX3298/MAX3299 are available in a 16-pin TSSOP-EP package. Gigabit Ethernet Optical Transmitter Fibre Channel Optical Transmitter ATM LAN Optical Transmitter Applications Features 7ps Deterministic Jitter () 22ps Deterministic Jitter () +3.0V to +5.5V Supply Voltage Selectable Laser Pinning (Common Cathode or Common Anode) (/) 30mA Laser Modulation Current Temperature Compensation of Modulation Current Automatic Laser Power Control or Constant Bias Current Integrated Safety Circuits Power-On Reset Signal QFN Package Available Ordering Information PART TEMP RANGE PPACKAGE CGI 0 C to +70 C 28 QFN (5mm x 5mm)** CHJ 0 C to +70 C 32 TQFP (5mm x 5mm) C/D 0 C to +70 C Dice* Ordering Information continued at end of data sheet. *Dice are designed to operate from T J = 0 C to +110 C, but are tested and guaranteed only at T A = +25 C. **Exposed pad. TOP VIEW POR PORDLY Pin Configurations VCC VCC MAX3289/ MAX Typical Application Circuits and Selector Guide appear at end of data sheet. LV VCC VCC QFN* *Exposed pad is connected to. Pin Configurations continued at end of data sheet. Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 MAX3289/ MAX3299 ABSOLUTE MAXIMUM RATINGS Supply Voltage at v to +7.0V Voltage at,, PORDLY,, LV,,,,,,,,,, V to ( + 0.5V) Voltage at,...( - 2V) to ( + 2V) Current into,, POR,...-1mA to +25mA Current into,...60ma Continuous Power Dissipation (T A = +70 C) 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 32-Pin TQFP (derate 14.3mW/ C above +70 C) mW 28-Pin QFN (derate 28.7mW/ C above +70 C) mW 16-Pin TSSOP (derate 27mW/ C above +70 C) mW Operating Temperature Range...0 C to +70 C Operating Junction Temperature Range...0 C to +150 C Processing Temperature (die) C Storage Temperature Range C to +150 C Lead Temperature (soldering, 10s) C ( = +3.0V to +5.5V, T A = 0 C to +70 C, unless otherwise noted. Typical values are at = +3.3V, R = open and T A = +25 C; see Figure 1a.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Current Data Input Voltage Swing TTL Input Current TTL Input High Voltage TTL Input Low Voltage, Output High Voltage, Output Low Voltage BIAS GERATOR (Note 1) Current, Shutdown Current Sink Current Source Voltage Nominal Voltage Voltage During Fault Input Current Input Current POWER-ON RESET POR Threshold POR Hysteresis DETECTION Fault Threshold High Fault Threshold Low Fault Threshold I CC V ID V IH V IL V OH V OL V Figure 1a, R MOD = 1.82kΩ Total differential signal, peak-to-peak, Figure 1a 0 V PIN I OH = -100µA I OL = 1mA = = low, V 0.6V 0.8 = low, V - 1V 0.8 I 2mA, = APC loop is closed Common-cathode configuration Common-anode configuration Normal operation ( = low) V = LV = LV = open V + 5% V + 20% V - 20% V - 5% ma mv µa V V V V µa ma V V V µa µa V mv V Fault Threshold /MAX3288//MAX mv, Fault Threshold 0.9 V 2

3 ELECTRICAL CHARACTERISTICS (continued) ( = +3.0V to +5.5V, T A = 0 C to +70 C, unless otherwise noted. Typical values are at = +3.3V, R = open and T A = +25 C; see Figure 1a.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS SHUTDOWN I = 10µA, asserted Voltage at I = 15mA, not asserted V I = 1mA, not asserted LASER MODULATOR Data Rate series 1.25 series 2.5 Gbps Minimum Laser Modulation Current 2 ma Maximum Laser Modulation Current Tolerance of Modulation Current Modulation-Current Edge Speed Deterministic Jitter (Note 2) Random Jitter, RMS (Note 3) Shutdown Modulation Current Modulation-Current Temperature Coefficient Differential Input Resistance Output Resistance Input Bias Voltage LASER SAFETY CIRCUIT POR Delay t PORDLY R L 25Ω 30 R MOD = 1.9kΩ (i MOD = 30mA) R MOD = 13kΩ (i MOD = 5mA) % to 80% series series R MOD = 13kΩ (i MOD = 5mA) series series series series R MOD = 4.1kΩ (i MOD = 15mA) R MOD = 1.9kΩ (i MOD = 30mA) R MOD = 13kΩ (i MOD = 5mA) R MOD = 4.1kΩ (i MOD = 15mA) R MOD = 1.9kΩ (i MOD = 30mA) Tempco = max, R MOD = open; Figure 5 Tempco = min, R = open; Figure 5 C PORDLY =, / only Single ended PORDLY = open Fault Time t (Note 4) 22 Glitch Rejection at ma % ps ps ps µa ppm/ C Ω Ω V µs ms µs µs MAX3289/ MAX3299 3

4 MAX3289/ MAX3299 ELECTRICAL CHARACTERISTICS (continued) ( = +3.0V to +5.5V, T A = 0 C to +70 C, unless otherwise noted. Typical values are at = +3.3V, R = open and T A = +25 C; see Figure 1a.) (T A = +25 C, unless otherwise noted.) 100,000 10,000 PARAMETER Duration or Minimum Pulse Width Required to Reset a Latched Fault Reset After,, or POR Transition Asserted After = Low or = High POR DELAY vs. C PORDLY SYMBOL t t _RESET t RESET t SHUTDN toc01 CONDITIONS C = 0 C = 270pF / only, Figure 1b, C = open / only, Figure 1b, C = / only, Figure 1b / only, Figure 1b Note 1: Common-anode configuration refers to a configuration where =, =, and an NPN device is used to set the laser bias current. Common-cathode configuration refers to a configuration where =, =, and a PNP device is used to set the laser bias current. Note 2: Deterministic jitter measured with a repeating K28.5 bit pattern Deterministic jitter is the peak-topeak deviation from the ideal time crossings per ANSI X3.230, Annex A. Note 3: For Fibre Channel and Gigabit Ethernet applications, the peak-to-peak random jitter is 14.1 times the RMS jitter. Note 4: Delay from a fault on until is asserted high. 10, DURATION vs. C Typical Operating Characteristics toc02 MIN TYP MAX UNITS µs ns 6 µs EYE DIAGRAM µs µs toc03 DELAY (µs) DELAY (µs) , ,000 CAPACITANCE (pf) ,000 CAPACITANCE (pf) 50ps/div 2.5Gbps, 1310nm LASER, 27-1 PRBS, i MOD = 15mA 4

5 (T A = +25 C, unless otherwise noted.) OPTICAL OUTPUT QFN STARTUP (COM-ANODE CONFIGURATION) 5µs/div TQFP PIN toc04 TSSOP-EP MAX3287 MAX3297 MAX3289 MAX3299 Typical Operating Characteristics (continued) OPTICAL OUTPUT TSSOP-EP MAX3288 MAX3298 SHUTDOWN 10µs/div NAME toc05 EYE DIAGRAM 100ps/div 1.25Gbps, 1310nm LASER, PRBS, i mod = 15mA Pin Description FUNCTION 1 1 Inverting Fault Indicator. See Table 1. 2, 16, 19 N.C. No Connect 2 3 Noninverting Fault Indicator. See Table POR Power-On Reset. POR is a TTL-compatible output. See Figure 14. 4, 13, 19 5, 14, 22, 30 1, 6 1, 6 Ground 5 6 Enable TTL Input. Laser output is enabled only when is high and is low. If is left unconnected, the laser is disabled. toc06 MAX3289/ MAX PORDLY Inverting Enable TTL Input. Laser output is enabled only when is low or grounded and is high. If is left unconnected, the laser is disabled. Power-On Reset Delay. To extend the delay for the power-on reset circuit, connect a capacitor to PORDLY. See the Design Procedure section. 5

6 MAX3289/ MAX3299 QFN TQFP PIN TSSOP-EP MAX3287 MAX3297 MAX3289 MAX3299 TSSOP-EP MAX3288 MAX3298 NAME LV 10, 22, 23, 26 11, 25, 26, 29 3, 11, 14 3, 11, 14 Supply Voltage Pin Description (continued) FUNCTION Fault Delay Input. Determines the delay of the and outputs. A capacitor attached to ensures proper startup. (See Typical Operating Characteristics.) = : holds low and high. When =, = high, = low, and is within the operational range, the safety circuitry is inactive. Low-Voltage Operation. Connect to for 4.5V to 5.5V operation. Leave open for 3.0V to 5.5V operation (Table 2) Noninverting Data Input Inverting Data Input Reference Voltage. A resistor connected at to determines the laser power when APC is used with common-cathode lasers. Polarity Input. is used for programming the laser-pinning polarity (Table 4). Inverting Polarity Input. is used for programming the laser-pinning polarity (Table 4). Monitor Diode Connection. is used for automatic power control Laser Bias Current Monitor. Used for programming laser bias current in VCSEL applications. Shutdown Driver Output. Provides a redundant laser shutdown. Bias-Controlling Transistor Driver. Connects to the base of an external PNP or NPN transistor. 6

7 QFN PIN and and and TQFP CONDITION LV = and < 4.5V V > 2.95V = PIN Table 1. Typical Fault Conditions V < - 540mV TSSOP-EP MAX3287 MAX3297 MAX3289 MAX3299 V > 1.15 V (nom), V < 0.85 V (nom) = low or open, = high or open V and V 0.8V TSSOP-EP MAX3288 MAX3298 NAME EP EP EP Exposed Pad Pin Description (continued) Table 2. LV Operating Range LV Open Grounded FUNCTION Modulation-Current Output. See Typical Application Circuits. Modulation-Current Output. See Typical Application Circuits. Modulation-Current Set. The resistor at programs the temperature-stable component of the laser modulation current. Temperature-Compensation Set. The resistor at programs the temperature-increasing component of the laser modulation current. Ground. This must be soldered to the circuit board ground for proper thermal performance. See Layout Considerations. OPERATING VOLTAGE RANGE (V) >3.0 >4.5 MAX3289/ MAX3299 7

8 MAX3289/ MAX3299 VID *MURATA BLM11HA102 I CC R MOD MODULATION CONTROL 50Ω I OUT FERRITE BEAD* 50Ω i MOD 3/2 Figure 1a. Output Load for AC Specification POR OPTICAL OUT t PORDLY NOTE: TIMING IS NOT TO SCALE. Figure 1b. Fault Timing t t _RESET t RESET R L (OP) L = 3.9nH LASER EQUIVALT LOAD t SHUTDN ON RESET BY SHUTDOWN BY 25Ω i MOD L = 3.9nH R L = 25Ω VOLTS V V V ID = V - V CURRT i MOD DIFFERTIAL INPUT RESULTING SIGNAL TIME 100mVp-p MIN 830mVp-p MAX 200mVp-p MIN 1660mVp-p MAX Detailed Description The / series of laser drivers contain a bias generator with APC, laser modulator, power-on reset (POR) circuit, and safety circuitry (Figures 2a and 2b). Bias Generator Figure 3 shows the bias generator circuitry containing a power-control amplifier, controlled reference voltage, smooth-start circuit, and window comparator. The bias generator combined with an external PNP or NPN transistor provides DC laser current to bias the laser in a lightemitting state. When there is a monitor diode () in the laser package, the APC circuitry adjusts the laser-bias current to maintain average power over temperature and changing laser properties. The input is connected to 8

9 LV PORDLY PORDLY POR POR CIRCUIT SAFETY BIAS GERATOR LASER MODULATOR LV SMOOTH- START POR POR CIRCUIT Figure 2a. Simplified Laser Driver Functional Diagram SAFETY CIRCUITRY the anode or cathode of a monitor photodiode or to a resistor-divider, depending on the specific application circuit. Three application circuits are supported: common-cathode laser with photodiode, commoncathode laser without photodiode, and common- anode laser with photodiode (as shown in the Design Procedure section). The and inputs determine the laser pinning (common cathode, common anode) (Table 4). The smooth-start circuitry prevents current spikes to the laser during power-up or enable; this ensures compliance with safety requirements and extends the life of the laser. The power-control amplifier drives an external transistor to control the laser bias current. In a fault condition, the power-control amplifier s output is disabled (high 1.7V +1.7V CONTROLLED ERCE GERATOR V 1.97V 1.53V BIAS GERATOR MAX3289/ MAX3299 INPUT BUFFER LASER MODULATOR 50Ω 50Ω MODULATION CURRT GERATOR R R MOD Figure 2b. Laser Driver Functional Diagram 9

10 MAX3289/ MAX3299 impedance). This ensures that the PNP or NPN transistor is turned off, removing the laser-bias current. (See the Applications Information section.) The pin provides a controlled reference voltage dependent upon the voltage at. The voltage at is V = ( - V ). A resistor connected at determines the laser power when APC is used with common-cathode lasers. See the Design Procedure section for setting the laser power. Modulation Circuitry The modulator circuitry consists of an input buffer, current generator, and high-speed current switch (Figure 4). The modulator drives up to 30mA of modulation current into a 25Ω load. Many of the modulator performance specifications depend on the total modulator current (IOUT) (Figure 1a). To ensure good driver performance, the voltage at and must not be less than VCC - 1V. The amplitude of the modulation current is set with resistors at the and temperature coefficient () pins. The resistor at (RMOD) programs the temperature-stable portion of modulation current, while the resistor at (R) programs the temperatureincreasing portion of the modulation current. Figure 5 shows modulation current as a function of temperature for two extremes: R is open (the modulation current has zero temperature coefficient) and RMOD is open (the modulation temperature coefficient is 4000ppm). Intermediate tempco values of modulation current can be obtained as described in the Design Procedure section. Table 3 is the R and RMOD selection table. Safety Circuitry The laser driver can be used with two popular safety systems. APC maintains laser safety using local feedback. Safety features monitor laser driver operation and Table 3. R and RMOD Selection Table i MOD = 30mA i MOD = 15mA i MOD = 5mA TEMPCO (ppm/ C) R MOD R R MOD R R MOD R (kω) (kω) (kω) (kω) (kω) (kω) ARITY_ ABLE 2.95V SMOOTH- START _ +1.53V GLIH REJECT +1.97V POWER- CONTROL AMPLIFIER +1.7V CONTROLLED ERCE VOLTAGE V = ( - V ) ITOR_ Figure 3. Bias Generator Circuitry R 400Ω - 0.3V 400Ω 0.8V INPUT BUFFER MODULATION CURRT GERATOR 4000ppm/ C ERCE _ CURRT SWIH ABLE Figure 4. Laser Modulator Circuitry R MOD WINDOW COMPARATOR ABLE 50Ω - 540mV 50Ω CURRT AMPLIFIER 0.8V 1.2V ERCE MOD_ 10

11 force a shutdown if a fault is detected. The shutdown condition is latched until reset by a toggle of,, or power. Another safety system, Open Fiber Control (OFC), uses safety interlocks to prevent eye hazards. To accommodate the OFC standard, the / series provide dual enable inputs and dual fault outputs. The safety circuitry contains fault detection, dual enable inputs, latched fault outputs, and a pulse generator (Figure 6). Safety circuitry monitors the APC circuit to detect unsafe levels of laser emission during single-point failures. A single-point failure can be a short to or, or between any two IC pins. imod/(imod AT+ 52 C) R 1.9kΩ R MOD = OP TEMPCO = 4000ppm/ C R = OP TEMPCO = 50ppm/ C JUNCTION TEMPERATURE ( C) Figure 5. Modulation Current vs. Temperature for Maximum and Minimum Temperature Coefficient (FROM POR CIRCUIT) _ ITOR ARITY MOD_ DETECTION Pulse Generator During startup, the laser is not emitting light and the APC loop is not closed, triggering a fault signal. To allow startup, an internal fault-delay pulse disables the safety system for a programmable period of time, allowing the driver to begin operation. The length of the pulse is determined by the capacitor connected at and should be set 5 to 10 times longer than the APC time constant. The internal safety features can be disabled by connecting to. Note that must be high, must be low, and must be in the operational range for laser operation. Fault Detection The / series has extensive and comprehensive fault-detection features. All critical nodes are monitored for safety faults, and any node voltage that differs significantly from its expected value results in a fault (Table 1). When a fault condition is detected, the laser is shut down. See the Applications Information section for more information on laser safety. Shutdown The laser drivers offer dual redundant bias shutdown mechanisms. The output drives an optional external MOSFET semiconductor. The bias and modulation drivers have separate, internal disable signals. Latched Fault Output Two complementary outputs are provided with the / series. In the event of a fault, these outputs latch until one of three events occurs: 1) The power is switched off, then on. PULSE GERATOR t R Q RESET DOMINANT LAH S MAX3289/ MAX3299 ABLE Figure 6. Simplified Safety Circuit Schematic 11

12 MAX3289/ MAX3299 LV 25k 36k 28k 1.2V BANDGAP Figure 7. Power-On Reset Circuit PORDLY VARIABLE DELAY 2) is switched low, then high. 3) is switched to high, then low. = 0.7s/µF C PORDLY Power-On Reset (POR) Figure 7 shows the POR circuit for the / series devices. A POR signal asserts low when is in the operating range. The voltage operating range is determined by the LV pin, as shown in Table 2. POR contains an internal delay to reject noise on during power-on or hot-plugging. The delay can be extended by adding capacitance to the PORDLY pin. The POR comparator includes hysteresis to improve noise rejection. The laser driver is shut down while is out of the operating range. Design Procedure Select Laser Select a communications-grade laser with a rise time of 260ps or better for 1.25Gbps, or 130ps or better for 2.5Gbps applications. To obtain the / s AC specifications, the instantaneous output voltage at must remain above - 1V at all times. Select a high-efficiency laser that requires low modulation current and generates low-voltage swing at. Laser package inductance can be reduced by trimming the leads. Typical package leads have inductance of 25nH/in (1nH/mm); this inductance causes a larger voltage swing across the laser. A compensation filter network can also be used to reduce ringing, edge speed, and voltage swing. POR Programming the Modulation Current Resistors at the and pins set the amplitude of the modulation current. The resistor R MOD sets the temperature-stable portion of the modulation current while the resistor R sets the temperatureincreasing portion of the modulation current. To determine the appropriate temperature coefficient from the slope efficiency (α) of the laser, use the following equation: Laser tempco = where α is the slope of the laser output power to the laser current. For example, suppose a laser has a slope efficiency α 25 of 0.021mW/mA at +25 C, which reduces to 0.018mW/mA at +70 C. Using the above equation will produce a laser tempco of -3175ppm/ C. To obtain the desired modulation current and tempco for the device, the following two equations can be used to determine the required values of R MOD and R : ( R + 250Ω ) 52 tempco RMOD = 250Ω ( tempco) where tempco = -laser tempco. Figure 8a shows a family of curves derived from these equations. The straight diagonal lines depict constant tempcos. The curved lines represent constant modulation currents. If no temperature compensation is desired, Figure 8b displays a series of curves that show laser modulation current with respect to R MOD for different loads. The following useful equations were used to derive Figure 8a and the equations at the beginning of this section. The first assumes R L = 25Ω. imod = 51 α α ( 70 C 25 C) 021. R = tempco imod 115. RMOD + Ω R + Ω A ( + ( T C) ) imod( 70 C) = imod( 25 C) + imod( 25 C) ( tempco)( 70 C 25 C) A [ ] ( ) 250 Ω [ ppm/ C] [ ] Programming the Bias Current/APC Three application circuits are described below: common-cathode laser with photodiode, common-cathode laser without photodiode, and common-anode laser α 12

13 R (kω) Table 4. Pin Setup for Each Laser Configuration Type DEVICE / 1 500ppm 1000ppm 1500ppm R L = 25Ω VCC 2000ppm R MOD (kω) MAX3287/MAX ppm 3000ppm 3500ppm 5mA 10mA 15mA 20mA 25mA 30mA Figure 8a. R vs. R MOD for Various Conditions LASER MODULATION CURRT (imod) (ma) Ω LOAD NOTE: R = OP 25Ω LOAD 50Ω LOAD R MOD (kω) Figure 8b. Laser-Modulation Current vs. R MOD DESCRIPTION Common cathode with photodiode with photodiode. The and inputs determine the laser pinning (common cathode, common anode) and affect the smooth-start circuits (Table 4). Common Cathode with Photodiode (Optical Feedback) In the common cathode with photodiode configuration, a servo control loop is formed by external PNP Q1, the laser diode, the monitor diode, RSET, and the powercontrol amplifier (Figure 9). The voltage at is stabilized to 1.7V. The monitor photodiode current (I D ) is set by (V - V) / RSET = 0.95 / RSET. Determine the desired monitor current (ID), then select RSET = 0.95 / ID. The APC loop is compensated by C. A capacitor must be placed from to VCC to ensure lownoise operation and to reject power-supply noise. The time constant governs how quickly the laser bias current reacts to a change in the average total laser current (I + imod). A capacitance of 0.1µF is sufficient to obtain a loop time constant in excess of 1µs, provided that RDEG is chosen appropriately. Resistor R DEG may be necessary to ensure the APC loop s stability when low bias currents are desired. The voltage across R DEG should not be any larger than 250mV at maximum bias current. The discrete components used with the common cathode with photodiode configuration are as follows: RSET = 0.95 / ID C = 0.1µF (typ) RDEG = 0.25 / I BIAS(MAX) LASER PINNING MAX3289/ MAX3299 / VCC MAX3288/MAX3298 Common cathode without photodiode / MAX3289/MAX3299 VCC Common anode with photodiode / VCC VCC Not allowed; fault occurs / Not allowed; fault occurs 13

14 MAX3289/ MAX3299 Q1 = general-purpose PNP, β >100, f t > 5MHz B1 = ferrite bead (see Bias Filter section) M1 = general-purpose PMOS device (optional) Common Cathode with Current Feedback In the common-cathode configuration with current feedback, a servo control loop is formed by an external PNP transistor (Q1), R, the controlled-reference voltage block, RSET, R, and the power-control amplifier (Figure 10). The voltage at is stabilized to 1.7V. The voltage at is set by the resistors R SET and R. As in the short-wavelength configuration, a 0.1µF C connected between and VCC is MAX3287 MAX3297 I D R SET PHOTO DIODE Figure 9. Common-Cathode Laser with Photodiode MAX3288 MAX3298 R SET I D /96 ONLY R /96 ONLY sufficient to obtain approximately a 1µs APC loop time constant. This improves power-supply noise rejection. To select the external components: 1) Determine the required laser bias current: IBIAS = ITH + imod / 2 2) Select R and RSET. Maxim recommends RSET = 1kΩ, R = 5kΩ, which results in - V 250mV. 3) Select R where R = 250mV / I BIAS, assuming R SET = 1kΩ and R = 5kΩ. CONTROLLED ERCE VOLTAGE V = 2.65V SMOOTH- START 1.7V CONTROLLED ERCE VOLTAGE V = 2.65V V ( - V ) SMOOTH- START 1.7V POWER-CONTROL AMPLIFIER POWER-CONTROL AMPLIFIER FERRITE BEAD B1 R FERRITE BEAD B1 M1 Q1 M1 Q1 R DEG LASER LASER I BIAS C I BIAS C Figure 10. Common Cathode with Current Feedback (PNP Configuration) 14

15 The relationship between laser bias current and R is shown in Figure 11. The remaining discrete components used with the common cathode without photodiode configuration are as follows: Q1 = general-purpose PNP, β >100, ft > 5MHz B1 = ferrite bead (see Bias Filter section) M1 = general-purpose PMOS device (optional) C = 0.1µF (typ) Common Anode with Photodiode In the common-anode configuration with photodiode, a servo control loop is formed by an external NPN transistor (Q1), the laser diode, the monitor diode, R SET, and the power-control amplifier. The voltage at is stabilized to 1.7V. The monitor photodiode current is set by I D = V / R SET (Figure 12). Determine the desired monitor current (I D ), then select R SET = 1.7V / I D. LASER BIAS CURRT (ma) k 10k MAX3289 MAX3299 R (Ω) ITOR DIODE R SET R SET = 1kΩ R = 5kΩ Figure 11. Common Cathode without Photodiode Laser I D /96 ONLY SMOOTH- START 1.7V C and a degeneration resistor (R DEG ) must be connected to the bias transistor (in this case NPN) to obtain the desired APC loop time constant. This improves power-supply (and ground) noise rejection. A capacitance of 0.1µF is sufficient to obtain time constants of up to 5µs in most cases. The voltage across R DEG should not be larger than 250mV at maximum bias current. The discrete components used with the common anode with photodiode configuration are summarized as follows: R SET = 1.7 / ID C = 0.1µF (typ) R DEG = 0.25 / I BIAS(MAX) Q1 = general-purpose NPN, β > 100, f t > 5MHz B1 = ferrite bead (see Bias Filter section) M1 = general-purpose PMOS (optional) Programming POR Delay A capacitor may be added to PORDLY to increase the delay for which POR will be asserted low (meaning that is within the operational range) when powering up the part. The delay will be approximately: See Typical Operating Characteristics. POWER-CONTROL AMPLIFIER C t = PORDLY [] s ( ) LASER I BIAS FERRITE BEAD B1 Q1 R DEG C MAX3289/ MAX3299 Figure 12. Common Anode with Photodiode 15

16 MAX3289/ MAX3299 Designing the Bias Filter and Output Pullup Beads To reduce deterministic jitter, add a ferrite-bead inductor between the collector of the biasing transistor and either the anode or cathode of the laser, depending on type (see Typical Operating Characteristics). Use a ferrite-bead inductor with an impedance >100Ω between ƒ = 10MHz and ƒ = 2GHz, and a DC resistance < 3Ω. Maxim recommends the Murata BLM11HA102SG. These inductors are also desirable for tying the and pins to. Designing the Laser-Compensation Filter Network Laser package inductance causes the laser impedance to increase at high frequencies, leading to ringing, overshoot, and degradation of the output eye pattern. A lasercompensation filter network can be used to reduce the output load seen by the laser driver at high frequencies, thereby reducing output ringing and overshoot. The compensation components (RCOMP and C COMP ) are most easily determined by experimentation. Begin with RCOMP = 25Ω and CCOMP = 2pF. Increase CCOMP until the desired transmitter eye is obtained (Figure 13). Quick Shutdown To reduce laser shutdown time, a FET device can be attached to as shown in Figure 10. This will provide a typical laser power shutdown time of less than 10µs. Applications Information Laser Safety and IEC 825 The International Electrotechnical Commission (IEC) determines standards for hazardous light emissions from fiber optic transmitters. IEC 825 defines the maximum light output for various hazard levels. The / series provides features that facilitate compliance with IEC 825. A common safety requirement is single-point fault tolerance, whereby one unplanned short, open, or resistive connection does not cause excess light output. When these laser drivers are used, as shown in the Typical Operating Circuits, the circuits respond to faults as listed in Table 5. Using these laser drivers 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 applications, recognizing that Maxim products are not designed or authorized for use as components in systems intended for surgical implant POWER Figure 13. Laser Compensation UNCOMPSATED CORRECTLY COMPSATED OVERCOMPSATED TIME 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. Layout Considerations The / series comprises high-frequency products. Their performance largely depends upon the circuit board layout. Use a multilayer circuit board with a dedicated ground plane. Use short laser package leads placed close to the modulator outputs. Power supplies must be capacitively bypassed to the ground plane with surface-mount capacitors placed near the power-supply pins. The dominant pole of the APC circuit is normally located at. To prevent a second pole in the APC (that can lead to oscillations), ensure that parasitic capacitance at is minimized. Common Questions Laser output is ringing or contains overshoot. This is often caused by inductive laser packaging. Try reducing the length of the laser leads. Modify the compensation components to reduce the driver s output edge speed (see Design Procedure). Extreme ringing can be caused by low voltage at the OUT± pins. This may indicate that pullup beads or a lower modulation current are needed. Low-frequency oscillation on the laser output. This is more prevalent at low temperatures. The APC may be oscillating. Try increasing the value of C or increasing the value of R DEG. Ensure that the parasitic capacitance at the node is kept very small (<10pF). The APC is not needed. Connect to ground to disable fault detection. Connect to and to. and can be left open. 16

17 Table 5. Circuit Response to Various Single-Point Faults PIN NAME POR CIRCUIT RESPONSE TO OVERVOLTAGE OR SHORT TO Does not affect laser power Does not affect laser power Normal condition for circuit operation Fault state* occurs CIRCUIT RESPONSE TO UNDERVOLTAGE OR SHORT TO GROUND Does not affect laser power Does not affect laser power PORDLY LV (also MAX3288/98) (also MAX3287/97/ 89/99), Does not affect laser power Fault state* occurs Does not affect laser power If is a TTL HIGH, a fault state* occurs; otherwise, the circuit is in normal operation If is a TTL HIGH, a fault state* occurs; otherwise, the circuit is in normal operation In common cathode without photodiode configuration, a fault state* occurs; otherwise, does not affect laser power Does not affect laser power. If optional FET is used, the laser output is shut off. Any fault that occurs cannot be reset. Does not affect laser power. Does not affect laser power Fault state* occurs Fault state* occurs Does not affect laser power Does not affect laser power Fault state* occurs Normal condition for circuit operation Fault state* occurs if is less than +4.5V If is a TTL LOW, a fault state* occurs; otherwise, the circuit is in normal operation If is a TTL LOW, a fault state* occurs; otherwise, the circuit is in normal operation Fault state* occurs Does not affect laser power Does not affect laser power Does not affect laser power In common-cathode configurations, a fault state* occurs; otherwise, does not affect laser power Fault state* occurs, Does not affect laser power Does not affect laser power In common-cathode configurations, the laser bias current is shut off. In common anode, high laser power triggers a fault state.* Shutdown occurs if a shutdown FET (M1) is used. If shutdown FET is not used, other means must be used to prevent high laser power. Does not affect laser power Does not affect laser power In common-anode configurations, the laser bias current is shut off. In common cathode, high laser power triggers a fault state.* Shutdown occurs if a shutdown FET (M1) is used (Figures 9, 10). Fault state* occurs Fault state* occurs MAX3289/ MAX3299 *A fault state will assert the pins, disable the modulator outputs, disable the bias output, and assert the pin. 17

18 MAX3289/ MAX3299 The modulator is not needed. Leave and open. Connect to VCC, to, and leave and OUT open. Wirebonding Die The / series uses bondpads with gold metalization. Make connections to the die with gold wire only, using ball-bonding techniques. Wedge bonding is not recommended. Bondpad size is 4mil square. Die thickness is typically 15mils (0.38mm). 2.5k Figure 14. Logic Outputs 4k 0.2pF,, POR PACKAGE 1.5nH 1pF 50Ω Interface Models Figures show typical input/output models for the / series of laser drivers. If dice are used, replace the package parasitic elements with bondwire parasitic elements. 550Ω Figure 15. Output 50Ω 1pF PACKAGE 1.5nH 10k 0.2pF 60Ω Figure 16. Modulator Outputs 18

19 40Ω 1.5nH 1.5nH INPUT COM-MODE VOLTAGE - 0.3V R IN Q1, Q2 > 100kΩ Figure 17. Data Inputs 0.2pF 0.2pF PACKAGE 1pF 1pF 400Ω 400Ω Q1 Q2 MAX3289/ MAX Ω Figure 18. Output 19

20 MAX3289/ MAX3299 TOP VIEW N.C. POR PORDLY DATA RATE/DEVICE 1.25Gbps TQFP Ordering Information (continued) VCC VCC LV VCC 2.5Gbps PART TEMP RANGE PPACKAGE MAX3287CUE 0 C to +70 C 16 TSSOP-EP** MAX3288CUE 0 C to +70 C 16 TSSOP-EP** MAX3289CUE 0 C to +70 C 16 TSSOP-EP** VCC N.C N.C. CGI 0 C to +70 C 28 QFN (5mm x 5mm)** CHJ 0 C to +70 C 32 TQFP (5mm x 5mm) C/D 0 C to +70 C Dice* COM ANODE WITH PHOTODIODE Longwave MAX3297CUE 0 C to +70 C 16 TSSOP-EP** MAX3298CUE 0 C to +70 C 16 TSSOP-EP** MAX3299CUE 0 C to +70 C 16 TSSOP-EP** LASER CONFIGURATION COM CATHODE WITH PHOTODIODE Shortwave or VCSEL MAX3287 MAX3289 MAX3297 MAX3299 TSSOP-EP* COM CATHODE WITH PHOTODIODE VCSEL Selector Guide Pin Configurations (continued) MAX3288 MAX3298 TSSOP-EP* PACKAGE 32 TQFP/28 QFN/Dice MAX3287 MAX TSSOP-EP MAX3288 MAX TSSOP-EP MAX3289 MAX TSSOP-EP *EXPOSED PAD IS CONNECTED TO. *Dice are designed to operate from T J = 0 C to +110 C, but are tested and guaranteed only at T A = +25 C. **Exposed pad. 20

21 / COM-CATHODE VCSEL WITH PHOTODIODE DATA INPUT 115Ω / COM-CATHODE VCSEL WITHOUT PHOTODIODE DATA INPUT 115Ω PORDLY POR LV PORDLY POR LV +3.0V TO +5.5V R R MOD R SET +3.0V TO +5.5V Typical Application Circuits C 0.1µF 25Ω C 0.1µF 25Ω C COMP R COMP C COMP R COMP R 5k PMOSFET (OPTIONAL) PNP TRANSISTOR FERRITE BEAD R PNP TRANSISTOR FERRITE BEAD MAX3289/ MAX3299 R R MOD R SET 1k 21

22 MAX3289/ MAX3299 / COM-ANODE LASER WITH PHOTODIODE DATA INPUT 115Ω MAX3287/MAX3297 COM-CATHODE VCSEL WITH PHOTODIODE DATA INPUT 115Ω PORDLY POR LV Typical Application Circuits (continued) +3.0V TO +5.5V MAX3287 MAX Ω R R MOD R SET +3.0V TO +5.5V C 0.1µF C COMP R COMP C 0.1µF C COMP 18Ω FERRITE BEAD NPN TRANSISTOR R DEG R DEG PNP TRANSISTOR FERRITE BEAD 25Ω R COMP R R MOD R SET 22

23 MAX3288/MAX3298 COM-CATHODE VCSEL WITHOUT PHOTODIODE DATA INPUT 115Ω MAX3289/MAX3299 COM-ANODE LASER WITH PHOTODIODE DATA INPUT 115Ω MAX3288 MAX3298 MAX3289 MAX3299 Typical Application Circuits (continued) +3.0V TO +5.5V R R MOD R SET 1k +3.0V to +5.5V C 0.1µF 25Ω 25Ω C COMP R COMP C COMP R COMP 18Ω R 5k R PNP TRANSISTOR FERRITE BEAD FERRITE BEAD MAX3289/ MAX3299 C 0.1µF NPN TRANSISTOR R R SET R MOD R DEG 23

24 MAX3289/ MAX3299 LV PORDLY HF34Z-1Z N.C " (1.346mm) POR TRANSISTOR COUNT: 1154 SUBSTRATE CONNECTED TO 0.072" (1.829mm) LV HF34Z PORDLY N.C. Chip Topographies 0.053" (1.346mm) POR TRANSISTOR COUNT: 1154 SUBSTRATE CONNECTED TO 0.072" (1.829mm 24

25 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to 32L QFN.EPS MAX3289/ MAX

26 MAX3289/ MAX3299 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to 32L,TQFP.EPS 26

27 Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to TSSOP.EPS MAX3289/ MAX3299 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. 27 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.