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MAX3735A
EVALUATION KIT AVAILABLE
2.7Gbps, Low-Power SFP Laser Driver
General Description
The MAX3735A is a +3.3V laser driver for SFP/SFF appli-
cations from 155Mbps up to 2.7Gbps. The device accepts
differential input 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 exter-
nal components. The MAX3735A is fully compliant with the
SFP MSA timing and the SFF-8472 transmit diagnostic
requirements.
An automatic power-control (APC) feedback loop is incor-
porated to maintain a constant average optical power over
temperature and lifetime. The wide modulation current
range of 10mA to 60mA (up to 85mA AC-coupled) and bias
current of 1mA to 100mA make this product ideal for driving
FP/DFB laser diodes in fiber-optic modules. The resistor
range for the laser current settings is optimized to interface
with the DS1858 SFP controller IC.
The MAX3735A provides transmit-disable control, a
single-point latched transmit-failure monitor output, photo-
current monitoring, and bias-current monitoring to indicate
when the APC loop is unable to maintain the average
optical power.
The MAX3735A is available in a 4mm x 4mm TQFN pack-
age and operates over the extended temperature range of
-40°C to +85°C.
Applications
● Gigabit Ethernet SFP/SFF Transceiver Modules
● 1G/2G Fibre Channel SFP/SFF Transceiver Modules
● Multirate OC3 to OC48-FEC SFP/SFF Transceiver
Modules
Typical Application Circuit
Features
● Fully Compliant with SFP and SFF-8472 MSAs
● Programmable Modulation Current from 10mA to
60mA (DC-Coupled)
● Programmable Modulation Current from 10mA to
85mA (AC-Coupled)
● Programmable Bias Current from 1mA to 100mA
● Edge Transition Times <51ps
● 27mA (typ) Power-Supply Current
● Multirate 155Mbps to 2.7Gbps Operation
● Automatic Average Power Control
● On-Chip Pullup Resistor for TX_DISABLE
● 24-Pin 4mm x 4mm TQFN package
Ordering Information appears at end of data sheet.
+3.3V
+3.3V
OPTIONAL SHUTDOWN
CIRCUITRY
SERDES
0.1µF
0.1µF
IN+
IN-
DS1858/DS1859
CONTROLLER
H0
IC H1
MON1
M0N2
M0N3
+3.3V
MAX3735A
OUT-
OUT+
OUT+
BIAS
MD
+3.3V
15
10
FERRITE BEAD
CMD
0.01µF
CAPC
RBC_MON
RPC_MON
REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE
19-2529; Rev 4; 1/13

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MAX3735A
2.7Gbps, Low-Power SFP Laser Driver
Absolute Maximum Ratings
Supply Voltage, VCC.............................................-0.5V to +6.0V
Current into BIAS, OUT+, OUT-...................... -20mA to +150mA
Current into MD..................................................... -5mA to +5mA
Voltage at IN+, IN-, TX_DISABLE, TX_FAULT,
SHUTDOWN......................................... -0.5V to (VCC + 0.5V)
Voltage at BIAS, PC_MON, BC_MON,
MODSET, APCSET............................... -0.5V to (VCC + 0.5V)
Voltage at OUT+, OUT-............................ +0.5V to (VCC + 1.5V)
Voltage at APCFILT1, APCFILT2..............................-0.5V to +3V
Continuous Power Dissipation (TA = +70°C )
24-Lead Thin QFN (derate 27.8mW/°C
above +70°C).............................................................2222mW
Operating Ambient Temperature Range (TA)...... -40°C to +85°C
Storage Ambient Temperature Range............... -55°C to +150°C
Die Attach Temperature....................................................+400°C
Lead Temperature (soldering, 10s).................................. +300°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.
Package Information
PACKAGE TYPE: 24-PIN TQFN
Package Code
Outline Number
Land Pattern Number
T2444+3
21-0139
90-0021
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.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.
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Maxim Integrated 2

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MAX3735A
2.7Gbps, Low-Power SFP Laser Driver
Electrical Characteristics
(VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values at VCC = +3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
POWER SUPPLY
Power-Supply Current
I/O SPECIFICATIONS
Differential Input Voltage
Common-Mode Input Voltage
Differential Input Resistance
TX_DISABLE Input Pullup
Resistance
SYMBOL
ICC
VID
RPULL
TX_DISABLE Input Current
TX_DISABLE Input High Voltage
TX_DISABLE Input Low Voltage
TX_FAULT Output High Voltage
TX_FAULT Output Low Voltage
SHUTDOWN Output High Voltage
SHUTDOWN Output Low Voltage
BIAS GENERATOR
Bias On-Current Range
Bias Off-Current
VIH
VIL
VOH
VOL
VOH
VOL
IBIAS
IBIASOFF
Bias Overshoot
Bias-Current Monitor Gain
IBC_MON
Bias-Current Monitor Gain
Stability
AUTOMATIC POWER-CONTROL LOOP
MD Reverse Bias Voltage
MD Average Current Range
IMD
Average Power-Setting Stability
Average Power Setting Accuracy
MD-Current Monitor Gain
IPC_MON
MD-Current Monitor Gain Stability
CONDITIONS
MIN TYP MAX
Excludes the laser bias and modulation
currents (Note 2)
27 50
VID = (VIN+) - (VIN-), Figure 1
200 2400
0.6 x VCC
85 100 115
4.7 7.4 10.0
VHIGH = VCC
VLOW = GND, VCC = 3.3V, RPULL = 7.4kΩ
-450
2
IOH = 100µA sourcing (Note 3)
IOL = 1mA sinking (Note 3)
IOH = 100µA sourcing
IOL = 100µA sinking
2.4
VCC - 0.4
15
0.8
0.4
0.4
Current into BIAS pin
1 100
Current into BIAS pin during TX_FAULT or
TX_DISABLE
100
During SFP module hot plugging
(Notes 4, 5, 11)
10
External resistor to GND defines the voltage
gain, IBIAS = 1mA, RBC_MON = 69.28kΩ
10.0
12
13.5
IBIAS = 100mA, RBC_MON = 693.25Ω
11.5 13 13.5
1mA ≤ IBIAS ≤ 100mA (Notes 4, 6)
-6
+6
18µA ≤ IMD ≤ 1500µA
Average current into MD pin
1.6
18 1500
APC closed loop
IBIAS = 1mA
(Notes 4, 7)
IBIAS = 100mA
APC Closed Loop
1mA ≤ IBIAS ≤ 100mA (Note 8)
-110
-650
-16
+110
+650
+16
External resistor to GND defines the voltage
gain; IMD = 18µA, RPC_MON = 50kΩ
0.9
1.1
IMD = 1.5mA, RPC_MON = 600Ω
0.95 1 1.05
18µA ≤ IMD ≤ 1500µA (Notes 4, 6)
-4
+4
UNITS
mA
mVP-P
V
kΩ
µA
V
V
V
V
V
V
mA
µA
%
mA/A
%
V
µA
ppm/°C
%
A/A
%
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Maxim Integrated 3

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MAX3735A
2.7Gbps, Low-Power SFP Laser Driver
Electrical Characteristics (continued)
(VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values at VCC = +3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
LASER MODULATOR
Modulation On-Current Range
Modulation Off-Current
Modulation-Current Stability
(Note 4)
Modulation-Current Absolute
Accuracy
Modulation-Current Rise Time
Modulation-Current Fall Time
Deterministic Jitter
Random Jitter
SAFETY FEATURES
Excessive Bias-Current
Comparator Threshold Range
Excessive MD-Current
Comparator Threshold Range
SFP TIMING REQUIREMENTS
TX_DISABLE Assert Time
TX_DISABLE Negate Time
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
IMOD
IMODOFF
Current into OUT+ pin; RL ≤ 15Ω, VOUT+,
VOUT- ≥ 0.6V (DC-coupled)
Current into OUT+ pin; RL ≤ 15Ω_, VOUT+,
VOUT- ≥ 2.0V (AC-coupled)
Current into OUT+ pin during TX_FAULT
or TX_DISABLE
IMOD = 10mA
IMOD = 60mA
10
10
-480
-255
60
mA
85
100 µA
+480
ppm/°C
+255
10mA ≤ IMOD ≤ 60mA (Note 8)
-15 +15 %
tR 20% to 80%, 10mA ≤ IMOD ≤ 60mA (Note 4)
tF 20% to 80%, 10mA ≤ IMOD ≤ 60mA (Note 4)
10mA ≤ IMOD ≤ 60mA at 2.67Gbps
(Notes 4, 9, 10)
At 1.25Gbps (K28.5 pattern)
At 622Mbps (Note 9)
At 155Mbps (Note 9)
RJ 10mA ≤ IMOD ≤ 60mA (Note 4)
42 65 ps
50 80 ps
18 38
11.5 ps
18
40
0.7 1.0 psRMS
TX_FAULT always occurs for VBC_MON
1.38V, TX_FAULT never occurs for
VBC_MON ≤ 1.22V
TX_FAULT always occurs for VPC_MON
1.38V, TX_FAULT never occurs for
VPC_MON ≤ 1.22V
1.22 1.30 1.39
1.22 1.30 1.39
V
V
t_off
t_on
Time from rising edge of TX_DISABLE to
IBIAS = IBIASOFF and IMOD = IMODOFF
(Note 4)
Time from falling edge of TX_DISABLE
to IBIAS and IMOD at 95% of steady state
when TX_FAULT = 0 before reset (Note 11)
0.14
5
µs
600 µs
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Maxim Integrated 4

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MAX3735A
2.7Gbps, Low-Power SFP Laser Driver
Electrical Characteristics (continued)
(VCC = +2.97V to +3.63V, TA = -40°C to +85°C. Typical values at VCC = +3.3V, IBIAS = 20mA, IMOD = 30mA, TA = +25°C, unless
otherwise noted.) (Note 1)
PARAMETER
TX_DISABLE Negate Time
During FAULT Recovery
TX_FAULT Reset Time or
Power-On Time
TX_FAULT Assert Time
TX_DISABLE to Reset
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Time from falling edge of TX_DISABLE
t_onFAULT to IBIAS and IMOD at 95% of steady state
when TX_FAULT = 1 before reset (Note 4)
60 200 ms
t_init
From power-on or negation of TX_FAULT
using TX_DISABLE (Note 4)
60 200 ms
t_fault
Time from fault to TX_FAULT on, CFAULT
20pF, RFAULT = 4.7kΩ (Note 4)
Time TX_DISABLE must be held high to
reset TX_FAULT (Note 4)
3.3 50
5
µs
µs
Note 1: Specifications at -40°C are guaranteed by design and characterization.
Note 2: Maximum value is specified at IMOD = 60mA, IBIAS = 100mA.
Note 3: TX_FAULT is an open-collector output and must be pulled up with a 4.7kΩ to 10kΩ resistor.
Note 4: Guaranteed by design and characterization.
Note 5: VCC turn-on time must be ≤ 0.8s, DC-coupled interface.
Note 6: Gain stability is defined by the digital diagnostic document (SFF-8472, rev. 9.0) over temperature and supply variation.
Note 7: Assuming that the laser diode to photodiode transfer function does not change with temperature.
Note 8: Accuracy refers to part-to-part variation.
Note 9: Deterministic jitter is measured using a 223 - 1 PRBS or equivalent pattern.
Note 10: Broadband noise is filtered through the network as shown in Figure 3. One capacitor,
C < 0.47μF, and one 0603 ferrite bead or inductor can be added (optional). This supply voltage filtering reduces the hot-
plugging inrush current. The supply noise must be < 100mVP-P up to 2MHz.
Note 11: CAPC values chosen as shown in Table 4.
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Maxim Integrated 5