MAX3996CGP ,3.0V to 5.5V / 2.5Gbps VCSEL and Laser DriverApplicationsFibre Channel Optical Transmitters0.01µ FVCCSHDNDRVTX_DISABLEVCSEL Transmitters0.01µ FG ..
MAX3996CTP+ ,+3.0V to +5.5V, 2.5Gbps VCSEL and Laser DriverApplicationsFibre Channel Optical Transmitters0.01μFVCC SHDNDRVTX_DISABLEVCSEL Transmitters0.01μFGi ..
MAX3996CTP+T ,+3.0V to +5.5V, 2.5Gbps VCSEL and Laser DriverELECTRICAL CHARACTERISTICS(V = 3.0V to 5.5V, T = 0°C to +70°C, unless otherwise noted. Typical valu ..
MAX399CEE+ ,Precision, 8-Channel/Dual 4-Channel, Low-Voltage, CMOS Analog MultiplexersApplicationsMAX398CGE 0°C to +70°C 16 QFN-EP* G1655-3Sample-and-Hold CircuitsMAX398CEE 0°C to +70°C ..
MAX399CPE+ ,Precision, 8-Channel/Dual 4-Channel, Low-Voltage, CMOS Analog MultiplexersMAX398/MAX39919-0299; Rev. 6; 6/07Precision, 8-Channel/Dual 4-Channel,Low-Voltage, CMOS Analog Mult ..
MAX399CSE ,Precision, 8-Channel/Dual 4-Channel, Low-Voltage, CMOS Analog MultiplexersApplicationsPART TEMP. RANGE PIN-PACKAGESample-and-Hold CircuitsMAX398CPE 0°C to +70°C 16 Plastic D ..
MAX749CSA ,Digitally Adjustable LCD Bias SupplyFeaturesThe MAX749 generates negative LCD-bias contrast' +2.0V to +6.0V Input Voltage Rangevoltages ..
MAX749CSA ,Digitally Adjustable LCD Bias SupplyFeaturesThe MAX749 generates negative LCD-bias contrast' +2.0V to +6.0V Input Voltage Rangevoltages ..
MAX749CSA+ ,Digitally Adjustable LCD Bias SupplyApplications______________Ordering InformationNotebook ComputersPART TEMP. RANGE PIN-PACKAGELaptop ..
MAX749CSA+T ,Digitally Adjustable LCD Bias SupplyApplications______________Ordering InformationNotebook ComputersPART TEMP. RANGE PIN-PACKAGELaptop ..
MAX749EPA ,Digitally Adjustable LCD Bias SupplyMAX74919-0143; Rev 1; 2/95Digitally Adjustable LCD Bias Supply_______________
MAX749ESA ,Digitally Adjustable LCD Bias SupplyApplications______________Ordering InformationNotebook ComputersPART TEMP. RANGE PIN-PACKAGELaptop ..
MAX3996CGP
3.0V to 5.5V / 2.5Gbps VCSEL and Laser Driver
General DescriptionThe MAX3996 is a high-speed laser driver for small-
form-factor (SFF) fiber optic LAN transmitters. It con-
tains a bias generator, a laser modulator, and
comprehensive safety features. Automatic power con-
trol (APC) adjusts the laser bias current to maintain
average optical power, regardless of changes in tem-
perature or laser properties. The driver accommodates
common anode or differential laser configurations. The
output current range of the MAX3996 is appropriate for
VCSELs and high-efficiency edge-emitting lasers.
The MAX3996 operates up to 3.2Gbps. It can switch up
to 30mA of laser modulation current and sink up to
60mA bias current. Adjustable temperature compensa-
tion is provided to keep the optical extinction ratio with-
in specifications over the operating temperature range.
The MAX3996 accommodates various laser packages,
including low-cost TO-46 headers. Low deterministic jit-
ter (9psP-P), combined with fast edge transitions,
(65ps) provides excellent margins compared to indus-
try-standard transmitter eye masks.
This laser driver provides extensive safety features to
guarantee single-point fault tolerance. Safety features
include a transmit disable, redundant shutdown, and
laser-bias monitoring. The safety circuit detects faults
that could cause hazardous light levels and immediate-
ly disables the laser output. The MAX3996 safety cir-
cuits are compliant with SFF and small-form-factor
pluggable (SFP) multisource agreements (MSA).
The MAX3996 is available in a compact 4mm ✕4mm,
20-pin QFN package and operates over a temperature
range of 0°C to +70°C.
ApplicationsFibre Channel Optical Transmitters
VCSEL Transmitters
Gigabit Ethernet Optical Transmitters
ATM LAN Optical Transmitters
10 Gigabit Ethernet WWDM
Features9psP-PDeterministic Jitter20-Pin QFN 4mm ✕4mm Package3.0V to 5.5V Supply Voltage Automatic Power ControlIntegrated Safety Circuits30mA Laser Modulation CurrentTemperature Compensation of Modulation
CurrentCompliant with SFF and SFP MSA
MAX3996
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
Typical Application Circuit
Ordering Information19-2194; Rev 1; 2/02
Pin Configuration appears at end of data sheet.
MAX3996
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VCC= 3.0V to 5.5V, TA= 0°C to +70°C, unless otherwise noted. Typical values are at VCC= 3.3V, TC pin not connected, TA=
+25°C.) (Figure 1)
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.
Supply Voltage at VCC...........................................-0.5V to +7.0V
Voltage at TX_DISABLE, PORDLY, MON1, COMP,
IN+, IN-, MD, BIAS, MODSET, TC..........-0.5V to (VCC+ 0.5V)
Voltage between COMP and MON2.....................................2.3V
Voltage between IN+ and IN-..................................................5V
Voltage at OUT+, OUT-.........................(VCC- 2V) to (VCC+ 2V)
Voltage between MON1 and MON2.....................................1.5V
Voltage between BIAS and MON2...........................................4V
Current into FAULT, SHDNDRV..........................-1mA to +25mA
Current into OUT+, OUT-....................................................60mA
Current into BIAS..............................................................120mA
Continuous Power Dissipation (TA= +70°C)
20-Pin QFN (derate 20mW/°C)...................................1600mW
Operating Ambient Temperature Range.............-40°C to +85°C
Operating Junction Temperature Range...........-40°C to +150°C
Storage Temperature Range.............................-55°C to +150°C
MAX3996
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
ELECTRICAL CHARACTERISTICS (continued)(VCC= 3.0V to 5.5V, TA= 0°C to +70°C, unless otherwise noted. Typical values are at VCC= 3.3V, TC pin not connected, TA=
+25°C.) (Figure 1)
Note 1:Supply current excludes bias and modulation currents.
Note 2:Deterministic jitter is the peak-to-peak deviation from the ideal time crossings measured with a K28.5 bit pattern
Note 3:AC characteristics guaranteed by design and characterization.
MAX3996
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
Typical Operating Characteristics(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driverypical Operating Characteristics (continued)(VCC= 3.3V, TA= +25°C, unless otherwise noted.)
MAX3996
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
Detailed DescriptionThe MAX3996 contains a bias generator with automatic
power control and smooth start, a laser modulator, a
power-on reset (POR) circuit, and safety circuitry
(Figure 3).
Bias GeneratorFigure 4 shows the bias generator circuitry that con-
tains a power-control amplifier, smooth-start circuitry,
and two bias-fault sensors. The power-control amplifier
combined with an internal NPN transistor provides DC
laser current to bias the laser in a light-emitting state.
The APC circuitry adjusts the laser bias current to main-
tain average power over temperature and changing
laser properties. The smooth-start circuitry prevents
current spikes to the laser during power-up or enable,
ensuring compliance with safety requirements and
extending the life of the laser.
The MD input is connected to the anode of a monitor
diode, which is used to sense laser power. The BIAS
output is connected to the cathode of the laser through
an inductor or ferrite bead. The power-control amplifier
drives a transistor to control the laser’s bias current. In
a fault condition (Table 1), the base of the bias-driving
transistor is pulled low to ensure that bias current is
turned off.
MAX3996
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser DriverFigure 1. Output Load for AC Specification
Figure 2. Required Input Signal and Modulation-Current Polarity
Figure 3. Laser Driver Functional Diagram
Figure 4. Bias Circuitry
MAX3996
Smooth-StartDuring startup, the laser does not emit light, and the
APC loop is not closed. The smooth-start circuit pulls
the MD pin to approximately 2.5V during the POR delay
and while TX_DISABLE is high. This causes the power-
control amplifier to shut off the bias transistor. When
POR delay is over and TX_DISABLE is low, the MD pin
is released and pulled to GND by RSETbecause there
is no laser power and thus no monitor diode current.
The output voltage of the power-control amplifier then
begins to increase. A capacitor attached to COMP
(CCOMP) slows the slew rate and allows a controlled
increase in bias current (Figure 11). Maxim recom-
mends CCOMP= 0.1µF.
Modulation CircuitryThe modulation circuitry consists of an input buffer, a
current mirror, and a high-speed current switch (Figure
5). The modulator drives up to 30mA of modulation cur-
rent into a 25Ωload.
Many of the modulator performance specifications
depend on total modulator current. To ensure good driver
performance, the voltage at either OUT+ or OUT- must
not be less than VCC- 1V.
The amplitude of the modulation current is set with resis-
tors at the MODSET and temperature coefficient (TC)
pins. The resistor at MODSET (RMOD) programs the
temperature-stable portion of the modulation current,
and the resistor at TC (RTC) programs the temperature-
increasing portion of the modulation current. Figure 6
shows modulation current as a function of temperature
for two extremes: RTCis open (the modulation current
has zero temperature coefficient), and RMODis open
(the modulation temperature coefficient is 4000ppm/°C).
Intermediate temperature coefficient values of the mod-
ulation current can be obtained as described in the
Design Procedure section. Table 2 is the RTCand RMOD
selection table.
Safety CircuitryThe safety circuitry contains a disable input, a fault
latch, and fault detectors (Figure 7). This circuitry moni-
tors the operation of the laser driver and forces a shut-
down if a single-point fault is detected. A single-point
fault can be a short to VCCor GND, or between any two
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser DriverFigure 5. Modulation Circuitry
IC pins. See Table 3 to view the circuit response to vari-
ous single-point failures. The shutdown condition is
latched until reset by a toggle of TX_DISABLE or VCC.
Fault DetectionAll 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
Applications Informationfor more information on laser
safety.
ShutdownThe laser driver offers redundant bias shutdown. The
SHDNDRV output drives an optional external transistor.
The bias and modulation drivers have separate internal
disable signals.
MAX3996
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
