Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - laser controller Laser diode driver (LWL) QSOP 20 Surface-mount

________________General Description

The MAX3766 is a complete, easy-to-program laser

driver for fiber optic LAN transmitters, optimized for

operation at 622Mbps. It includes a laser modulator,

automatic power control (APC), and a failure indicator

with latched shutdown.

Laser modulation current can be programmed up to

60mA at 622Mbps. A programmable modulation tem-

perature coefficient can be used to keep the transmit-

ted extinction ratio nearly constant over a wide

temperature range. The modulator operates at data

rates up to 1.25Gbps at reduced modulation current.

APC circuitry uses feedback from the laser’s monitor

photodiode to adjust the laser bias current, producing

constant output power regardless of laser temperature

or age. The MAX3766 supports laser bias currents up

to 80mA.

The MAX3766 provides extensive laser safety features,

including a failure indicator with latched shutdown and

a smooth start-up bias generator. These features help

ensure that the transmitter output does not reach haz-

ardous levels. The MAX3766 is available in a compact

20-pin QSOP and dice.

________________________Applications

622Mbps ATM Transmitters

1.25Gbps Fiber Optic LAN Transmitters

1.25Gbps Ethernet Transmitters

____________________________Features

♦ 60mA Modulation Current

♦ 80mA Bias Current

♦ 200ps Edge Speed

♦ Modulation-Current Temperature Compensation

♦ Automatic Power Control

♦ Laser-Fail Indicator with Latched Shutdown

♦ Smooth Laser Start-Up

MAX3766

622Mbps LAN/WAN Laser Driver with

Automatic Power Control and Safety Shutdown

________________________________________________________________ Maxim Integrated Products 1

19-1249; Rev 1; 11/04

EVALUATION KIT

AVAILABLE

Ordering Information

*Dice are designed to operate over this range, but are tested and

guaranteed at T

= +25°C only. Contact factory for availability.

+Denotes lead-free package.

Typical Application Circuits appear at end of data sheet.

Pin Configuration

REF1

POWERSET

GNDOUTMOD

REF2

BIASMAX

TOP VIEW

BIAS

OUT+

OUT-

CCOUT

GND

IN+

IN-

GND

FAIL

SAFETYENABLE

MAX3766

QSOP

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 408-737-7600 ext. 3468.

PART TEMP RANGE PIN-PACKAGE

MAX3766EEP -40°C to +85°C 20 QSOP

MAX3766EEP+ -40°C to +85°C 20 QSOP

MAX3766E/D -40°C to +85°C Dice*

Summary of content (20 pages)

PAGE 1
9-1249; Rev 1; 11/04 KIT ATION EVALU E L B AVAILA 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown ____________________________Features The MAX3766 is a complete, easy-to-program laser driver for fiber optic LAN transmitters, optimized for operation at 622Mbps. It includes a laser modulator, automatic power control (APC), and a failure indicator with latched shutdown. Laser modulation current can be programmed up to 60mA at 622Mbps.
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MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown ABSOLUTE MAXIMUM RATINGS Supply Voltage, VCC, VCCOUT .................................-0.5V to 7.0V Voltage at IN+, IN-, ENABLE, SAFETY, FAIL ...........................................-0.5V to (VCC + 0.5V) Voltage at MOD, BIASMAX, POWERSET, TC ..........-0.5V to 4.0V Current out of REF1, REF2 .................................-0.1mA to 10mA Current into OUT+, OUT- ....................................
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622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown PARAMETER CONDITIONS Monitor-Diode Current Programmable Range MIN TYP 15 2.1 MAX UNITS 2000 µA 2.3 V Monitor-Diode Bias Voltage VCC - VMD 1.5 Upper MD Voltage for Failure Referenced to VCC -1.2 Lower MD Voltage for Failure Referenced to VCC Range of MD for No Failure Width of operating window, centered at nominal VMD REF1 Voltage for Failure Referenced to nominal VREF1 0.
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Typical Operating Characteristics (Typical Operating Characteristics are measured on the MAX3766 evaluation kit, VCC = +5.0V, TA = +25°C, unless otherwise noted.) DIE MODULATION CURRENT vs.
PAGE 5
622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown BIAS CURRENT vs. RBIASMAX (NO APC, OPEN-LOOP CONFIGURATION) DDJ (ps) IMD (mA) 1k 10k 100k 213 PRBS PATTERN 72 CONSECUTIVE ZEROS 100 0.001 100 180 120 NOMINAL = 2µA 10 2 - 1 PRBS PATTERN 140 0.
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22Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown MAX3766 Pin Description 6 PIN NAME FUNCTION 1 BIASMAX The current into BIASMAX sets the maximum laser bias current. Connecting BIASMAX directly to REF1 allows the largest possible bias current. 2 TC The resistance (RTC) between TC and REF1 programs the temperature coefficient of REF2. Connecting TC directly to REF1 produces the minimum tempco. Leaving TC unconnected produces the maximum tempco.
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622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown DIFFERENTIAL INPUT 250mV MIN 900mV MAX VINVIN+ SINGLE-ENDED INPUT 500mV MIN 1800mV MAX VIN- The differential PECL input signals are connected to the high-speed PECL input buffer at IN+ and IN-. The input impedance at IN+ and IN- is greater than 100kΩ, and the input bias current is less than 10µA. The MAX3766’s data inputs are not self-biasing. The common-mode input should be set by the external PECL termination circuitry.
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MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown RPOWERSET RMOD 5.
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622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown RPOWERSET = 1.55V I MOD − 300Ω The monitor-diode amplifier senses the current from the monitor photodiode at MD, provides gain, and adjusts the laser bias programming current (ILBP). The monitordiode amplifier forces the monitor-diode current to equal the current programmed at POWERSET. The monitor-diode amplifier can reduce the laser bias programming current, but cannot increase it.
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MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown OPEN COLLECTOR FAILURE (INTERNAL) FAIL SIMPLIFIED OPEN-COLLECTOR OUTPUT CIRCUIT RESET DOMINATE RS FLIP-FLOP S VCC OUT Q 200k SAFETY R OPEN COLLECTOR CSAFETY SHDN (INTERNAL) IN ENABLE 100k Figure 4.
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622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown Select Laser VCC Select a communications-grade laser with a rise time of 0.5ns or better for 622Mbps applications. The voltage swing at the OUT+ pin affects the output waveform, and is largely determined by the laser resistance, inductance, and modulation current. To obtain the MAX3766’s AC specifications, the output voltage at OUT+ must remain above VCC - 2.5V at all times.
PAGE 12
MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown Set Modulation-Current Tempco Compute the required modulation tempco from the slope efficiency of the laser at TA = +25°C and at a hot temperature. Then select the value of RTC from the Typical Operating Characteristics. For example, suppose a laser has a slope efficiency (SE) of 0.021mW/mA at +25°C, which reduces to 0.018mW/mA at +85°C.
PAGE 13
622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown MAX3766 UNCOMPENSATED OPTICAL POWER P1 CORRECTLY COMPENSATED PAVE OVERCOMPENSATED P0 500ps/div TIME Figure 7. Example Laser Compensation Calculate Power Consumption The MAX3766’s junction temperature must be kept below +150°C at all times. Calculate total power dissipated on the MAX3766 by laser power as follows: Power = VCC (ICC + IBIAS + IMOD) - (IMOD / 2 + IBIAS) VLASER.
PAGE 14
MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown Table 3. MAX3766 Fault Response in Latched Shutdown Configuration PIN CIRCUIT RESPONSE TO UNDERVOLTAGE OR SHORT TO GROUND Depending upon the setting of RPOWERSET, there is either no effect, or a latched shutdown. Bias current reduction causes a low laser output, resulting in a latched shutdown. High voltage on REF1 causes a failure and latched shutdown.
PAGE 15
622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown MAX3766 VCC VCC MAX3766 PECL OUTPUT IN 5.1k 50Ω VCC - 2V VCC VCC 68Ω RF OR NONPECL OUTPUT IN FAIL LASER RESET 5.1k MAX3766 OUT+ 100k FAIL 180Ω MAX3766 VCC TTL OR CMOS OUTPUT R2 2.87k R1 10kΩ MAX3766 Figure 10. External Laser Shutdown Circuit IN R3 11.8k SINGLE-ENDED TERMINATION IS SHOWN. THE OTHER INPUT SHOULD BE TERMINATED SIMILARLY, OR CONNECTED TO VCC - 1.3V. Figure 9.
PAGE 16
MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown INPUT OUTPUT OUT+ PACKAGE OUTPACKAGE 0.2pF 0.2pF 0.2pF 250Ω VIN+ 1.5nH Q1 1.5nH 1.5nH 0.4pF VCC VCC 1.5nH VCC 1pF VCC 2pF 1pF 250Ω Q2 VIN0.2pF PACKAGE VCC VCC 1.5nH 0.2pF BIAS 0.4pF VCC - 2.5 Q3 Q5 Q4 VCC - 2.5 VCC - 2.5 IBIAS IMOD Q1, Q2 INPUT BIAS CURRENT ≅ 1µA Q1, Q2 INPUT RESISTANCE ≅ 1MΩ Q3, Q4 OUTPUT RESISTANCE ≅ 100kΩ Q5 OUTPUT RESISTANCE ≅ 100kΩ Figure 11.
PAGE 17
622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown VCC FAILURE-INDICATION CONFIGURATION LASER 0.01µF VCC CMD ENABLE OUT- VCCOUT VCC MD OUT+ IN+ IN- BIAS VCC BIASMAX MAX3766 RFAIL 5.1k RPOWERSET POWERSET FAIL SAFETY REF1 TC MOD REF2 GNDOUT GND RMOD CONFIGURED FOR MINIMUM COMPONENT COUNT. VCC LATCHED SHUTDOWN CONFIGURATION LASER 0.01µF CMD RD VCC RCOMP ROUT- LBIAS CCOMP VCCOUT VCC ENABLE OUT- MD IN+ IN- OUT+ BIAS RBIASMAX VCC BIASMAX RFAIL 5.
PAGE 18
MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown ___________________Chip Topography IN+ IN- GND MOD GND REF2 TC VCC BIASMAX ENABLE REF1 0.056" (1.422mm) SAFETY POWERSET FAIL MD VCCOUT OUT- OUT+ BIAS GNDOUT 0.045" (1.143mm) TRANSISTOR COUNT: 725 SUBSTRATE CONNECTED TO GND AND GNDOUT.
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622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown QSOP.
PAGE 20
MAX3766 622Mbps LAN/WAN Laser Driver with Automatic Power Control and Safety Shutdown NOTES 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.