MAXIM MAX3738 Technical data
General Description
The MAX3738 is a +3.3V laser driver designed for multirate transceiver modules with data rates from
155Mbps to 2.7Gbps. Lasers can be DC-coupled to the
MAX3738 for reduced component count and ease of
multirate operation.
Laser extinction ratio control (ERC) combines the features
of automatic power control (APC), modulation compensation, and built-in thermal compensation. The APC loop
maintains constant average optical power. Modulation
compensation increases the modulation current in proportion to the bias current. These control loops, combined with thermal compensation, maintain a constant
optical extinction ratio over temperature and lifetime.
The MAX3738 accepts differential data input signals.
The wide 5mA to 60mA (up to 85mA AC-coupled) modulation current range and up to 100mA bias current
range, make the MAX3738 ideal for driving FP/DFB
lasers in fiber optic modules. External resistors set the
required laser current levels. The MAX3738 provides
transmit disable control (TX_DISABLE), single-point
fault tolerance, bias-current monitoring, and photocurrent monitoring. The device also offers a latched failure
output (TX_FAULT) to indicate faults, such as when the
APC loop is no longer able to maintain the average
optical power at the required level. The MAX3738 is
compliant with the SFF-8472 transmitter diagnostic and
SFP MSA timing requirements.
The MAX3738 is offered in a 4mm x 4mm, 24-pin thin
QFN package and operates over the extended -40°C to
+85°C temperature range.
Applications
Multirate OC-3 to OC-48 FEC Transceivers
Gigabit Ethernet SFF/SFP and GBIC
Transceivers
1Gbps/2Gbps Fibre Channel SFF/SFP and GBIC
Transceivers
Features
♦ Single +3.3V Power Supply
♦ 47mA Power-Supply Current
♦ 85mA Modulation Current
♦ 100mA Bias Current
♦ Automatic Power Control (APC)
♦ Modulation Compensation
♦ On-Chip Temperature Compensation
♦ Self-Biased Inputs for AC-Coupling
♦ Ground-Referenced Current Monitors
♦ Laser Shutdown and Alarm Outputs
♦ Enable Control and Laser Safety Feature
MAX3738
155Mbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
19-3162; Rev 1; 7/05
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Pin Configuration
Typical Application Circuit appears at end of data sheet.
+
Denotes lead-free package.
PART
MAX3738ETG -40°C to 85°C 24 Thin QFN T2444-3
MAX3738ETG+ -40°C to 85°C 24 Thin QFN T2444-3
TEMP
RANGE
PINPACKAGE
PKG
CODE
TOP VIEW
TH_TEMP
MODBCOMP
24 23 22 21 20 19
MODTCOMP
TX_DISABLE
THE EXPOSED PADDLE MUST BE SOLDERED TO SUPPLY
GROUND ON THE CIRCUIT BOARD.
PIN1 INDICATED BY + ON LEAD-FREE PACKAGE.
1
V
2
CC
3
IN+
4
IN-
V
5
CC
6
7 8 9 10 11 12
PC_MON
MAX3738
BC_MON
MODSET
APCSET
GND
SHUTDOWN
APCFILT2
APCFILT1
18
MD
V
17
OUT+
16
OUT-
15
V
14
BIAS
13
GND
TX_FAULT
CC
CC
MAX3738
155Mbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC= +2.97V to +3.63V, TA= -40°C to +85°C. Typical values are at VCC= +3.3V, I
BIAS
= 60mA, I
MOD
= 60mA, TA= +25°C, unless
otherwise noted.) (Notes 1, 2)
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 VCC...............................................-0.5V to +6.0V
IN+, IN-, TX_DISABLE, TX_FAULT, SHUTDOWN,
BC_MON, PC_MON, APCFILT1, APCFILT2,
MD, TH_TEMP, MODTCOMP, MODBCOMP,
MODSET, and APCSET Voltage.............-0.5V to (V
CC
+ 0.5V)
OUT+, OUT-, BIAS Current.............................-20mA to +150mA
Continuous Power Dissipation (T
A
= +85°C)
24-Pin TQFN (derate 20.8mW/°C above +85°C) .......1805mW
Operating Junction Temperature Range...........-55°C to +150°C
24-Pin TQFN (derate 20.8mW/°C above +85°C) ........1805mW
Storage Temperature Range .............................-55°C to +150°C
POWER SUPPLY
Supply Current I
Power-Supply Noise Rejection PSNR f ≤ 1MHz, 100mA
I/O SPECIFICATIONS
Differential Input Swing V
Common-Mode Input V
LASER BIAS
Bias-Current-Setting Range 1 100 mA
Bias Off Current TX_DISABLE = high 0.1 mA
Bias-Current Monitor Ratio I
LASER MODULATION
Modulation Current-Setting
Range
Output Edge Speed
Output Overshoot/Undershoot With 1pF between OUT+ and OUT- ±6%
Random Jitter (Notes 6, 7) 0.62 1.3 ps
Deterministic Jitter (Notes 6, 8)
Modulation-Current Temperature
Stability
Modulation-Current-Setting Error
Modulation Off Current TX_DISABLE = high 0.1 mA
AUTOMATIC POWER AND EXTINCTION RATIO CONTROLS
Monitor-Diode Input Current
Range
MD Pin Voltage 1.4 V
MD Current Monitor Ratio IMD / I
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CC
I
MOD
I
MD
CM
(Note 3) 47 60 mA
DC-coupled, Figure 1 0.2 2.4 V
ID
/ I
BIAS
BC_MON
(Note 5) 5 85 mA
20% to 80%
(Notes 6, 7)
2.7Gbps, 5mA ≤ I
1.25Gbps, 5mA ≤ I
622Mbps, 5mA ≤ I
155Mbps, 5mA ≤ I
(Note 6)
15Ω load,
T
= +25°C
A
Average current into the MD pin 18 1500 µA
PC_MON
(Note 4) 33 dB
P-P
5mA ≤ I
≤ 85mA 18 40
MOD
≤ 85mA 20 41
MOD
≤ 85mA 24 46
MOD
≤ 85mA 45 100
MOD
5mA ≤ I
10mA ≤ I
5mA ≤ I
10mA < I
≤ 85mA 65 80 ps
MOD
≤ 10mA ±175 ±600
MOD
≤ 85mA ±125 ±480
MOD
≤ 10mA ±20
MOD
≤ 85mA ±15
MOD
V
-
1.7
68 79 95 mA/mA
0.85 0.93 1.15 mA/mA
CC
/ 4
V
ID
ps
ppm/°C
P-P
V
RMS
P-P
%
MAX3738
155Mbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control
_______________________________________________________________________________________ 3
Note 1: AC characterization is performed using the circuit in Figure 2 using a PRBS 223- 1 or equivalent pattern.
Note 2: Specifications at -40°C are guaranteed by design and characterization.
Note 3: Excluding I
BIAS
and I
MOD
. Input data is AC-coupled. TX_FAULT open, SHUTDOWN open.
Note 4: Power-supply noise rejection (PSNR) = 20log
10(Vnoise (on VCC
) / ΔV
OUT
). V
OUT
is the voltage across the 15Ω load when IN+
is high.
Note 5: The minimum required voltage at the OUT+ and OUT- pins is +0.75V.
Note 6: Guaranteed by design and characterization.
Note 7: Tested with 00001111 pattern at 2.7Gbps.
Note 8: DJ includes pulse-width distortion (PWD).
ELECTRICAL CHARACTERISTICS (continued)
(VCC= +2.97V to +3.63V, TA= -40°C to +85°C. Typical values are at VCC= +3.3V, I
BIAS
= 60mA, I
MOD
= 60mA, TA= +25°C, unless
otherwise noted.) (Notes 1, 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
APC Loop Time Constant C
APC Setting Stability (Note 6) ±100 ±480 ppm/°C
APC Setting Accuracy TA = +25°C ±15 %
I
Compensation-Setting
MOD
Range by Bias
I
Compensation-Setting
MOD
Range by Temperature
Threshold-Setting Range for
Temperature Compensation
LASER SAFETY AND CONTROL
Bias and Modulation Turn-Off
Delay
Bias and Modulation Turn-On
Delay
Threshold Voltage at Monitor Pins V
INTERFACE SIGNALS
TX_DISABLE Input High V
TX_DISABLE Input Low V
TX_DISABLE Input Current
TX_FAULT Output Low Sinking 1mA, open collector 0.4 V
Shutdown Output High Sourcing 100µA VCC - 0.4 V
Shutdown Output Low Sinking 100µA 0.4 V
K K = ΔI
TC TC = ΔI
T
TH
REF
HI
LO
APC_FILT
(Note 6) +10 +60 °C
C
APC_FILT
(Note 6)
C
APC_FILT
(Note 6)
Figure 5 1.14 1.3 1.39 V
R
PULL
VHI = V
V
LO
= 0.01µF, ΔIMD / ΔI
/ ΔI
MOD
= 45kΩ (typ) 0.8 V
= GND -70 -140
BIAS
/ ΔT (Note 6) 0 1.0 mA/°C
MOD
= 0.01µF, ΔIMD / ΔI
= 0.01µF, ΔIMD / ΔI
CC
BIAS
BIAS
BIAS
= 1/70 3.3 µs
= 1/80
= 1/80
0 1.5 mA/mA
5µs
600 µs
2.0 V
15
µA
MAX3738
155Mbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VCC= +3.3V, C
APC
= 0.01µF, I
BIAS
= 20mA, I
MOD
= 30mA, TA= +25°C, unless otherwise noted.)
OPTICAL EYE DIAGRAM
(2.7Gbps, 2
7
- 1 PRBS, 2.3GHz FILTER)
MAX3738 toc01
54ps/div
1310nm FP LASER
r
e
= 8.2dB
OPTICAL EYE DIAGRAM
(1.25Gbps, 2
7
- 1 PRBS, 940MHz FILTER)
MAX3738 toc02
116ps/div
1310nm FP LASER
r
e
= 8.2dB
ELECTRICAL EYE DIAGRAM
(I
MOD
= 30mA, 2.7Gbps, 27 - 1 PRBS)
MAX3738 toc03
52ps/div
75mV/div
1pF BETWEEN OUT+
AND OUT-
SUPPLY CURRENT (ICC) vs. TEMPERATURE
(EXCLUDES BIAS AND MODULATION CURRENTS)
MAX3738 toc04
TEMPERATURE (°C)
SUPPLY CURRENT (mA)
80706050403020100-10-20-30
35
40
45
50
55
60
30
-40 90
3.63V
2.97V
3.3V
BIAS-CURRENT MONITOR RATIO
vs. TEMPERATURE
MAX3738 toc05
TEMPERATURE (°C)
I
BIAS
/I
BC_MON
(mA/mA)
807050 60-10 0 10 20 30 40-30 -20
72
74
76
78
80
82
84
86
88
90
70
-40 90
PHOTOCURRENT MONITOR RATIO
vs. TEMPERATURE
MAX3738 toc06
TEMPERATURE (°C)
I
MD
/I
PC_MON
(mA/mA)
807050 60-100 10203040-30 -20
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20
0.80
-40 90
MODULATION CURRENT vs. R
MODSET
MAX3738 toc07
R
MODSET
(kΩ)
I
MOD
(mA)
10
10
20
30
40
50
60
70
80
90
0
1 100
PHOTODIODE CURRENT vs. R
APCSET
MAX3738 toc08
R
APCSET
(kΩ)
I
MD
(mA)
101
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0
0.1 100
DETERMINISTIC JITTER
vs. MODULATION CURRENT
MAX3738 toc09
I
MOD
(mA)
DJ (ps
P-P
)
807050 6020 30 4010
5
10
15
20
25
30
35
40
45
50
0
090
2.7Gbps
MAX3738
155Mbps to 2.7Gbps SFF/SFP Laser Driver with
Extinction Ratio Control
_______________________________________________________________________________________
5
Typical Operating Characteristics (continued)
(VCC= +3.3V, C
APC
= 0.01µF, I
BIAS
= 20mA, I
MOD
= 30mA, TA= +25°C, unless otherwise noted.)
vs. MODULATION CURRENT
2.0
1.8
1.6
1.4
)
1.2
RMS
1.0
RJ (ps
0.8
0.6
0.4
0.2
0
090
TEMPERATURE COMPENSATION vs.
R
TH_TEMP
44
42
R
TH_TEMP
40
R
TH_TEMP
R
38
TH_TEMP
(mA)
R
= 2kΩ
TH_TEMP
MOD
I
36
34
32
RANDOM JITTER
I
(mA)
MOD
(R
MODTCOMP
= 12kΩ
= 7kΩ
= 4kΩ
= 10kΩ)
807050 6020 30 4010
MAX3738 toc10
MAX3738 toc13
TX_DISABLE
COMPENSATION (K) vs. R
10
1
K (mA/mA)
0.1
0.01
0.001 100
HOT PLUG WITH TX_DISABLE LOW
3.3V
V
CC
0V
LOW
FAULT
LOW
LASER
OUTPUT
R
MODBCOMP
t_init = 59.6ms
(kΩ)
MODBCOMP
1010.10.01
MAX3738 toc14
MAX3738 toc11
TX_DISABLE
TEMPERATURE COMPENSATION vs.
TH_TEMP
R
TH_TEMP
TH_TEMP
= 2kΩ
R
(R
MODTCOMP
= 12kΩ
TH_TEMP
= 7kΩ
= 4kΩ
TEMPERATURE (°C)
R
100
90
80
70
(mA)
MOD
I
R
60
R
TH_TEMP
50
40
30
-10 90
TRANSMITTER ENABLE
V
CC
3.3V
LOW
FAULT
HIGH
t_on = 23.8μs
LASER
OUTPUT
= 500Ω)
MAX3738 toc12
80706050403020100
MAX3738 toc15
LOW
V
FAULT
TX_DISABLE
LASER
OUTPUT
30
-10 10090
TEMPERATURE (°C)
TRANSMITTER DISABLE
CC
3.3V
LOW
HIGH
91.2ns
LOW
20ns/div
80706050403020100
MAX3738 toc16
V
PC_MON
FAULT
TX_DISABLE
LASER
OUTPUT
20ms/div
RESPONSE TO FAULT
EXTERNALLY
FORCED FAULT
400ns/div
MAX3738 toc17
t_fault = 160ns
V
PC_MON
FAULT
TX_DISABLE
LASER
OUTPUT
10μs/div
FAULT RECOVERY TIME
EXTERNALLY
FORCED FAULT
HIGH
t_init = 58ms
HIGH
40ms/div
MAX3738 toc18
LOW
LOWLOW
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