19-3161; Rev 2; 6/11
KIT
ATION
EVALU
BLE
AVAILA
155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
General Description
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
MAX3646
The MAX3646 is a +3.3V laser driver designed for mul-
tirate transceiver modules with data rates from
155Mbps to 622Mbps. Lasers can be DC-coupled to
the MAX3646 for reduced component count and ease
of multirate operation.
Laser extinction ratio control (ERC) combines the features
of automatic power control (APC), modulation compensa-
tion, and built-in thermal compensation. The APC loop
maintains constant average optical power. Modulation
compensation increases the modulation current in pro-
portion to the bias current. These control loops, com-
bined with thermal compensation, maintain a constant
optical extinction ratio over temperature and lifetime.
The MAX3646 accepts differential data input signals.
The wide 5mA to 60mA (up to 85mA AC-coupled) mod-
ulation current range and up to 100mA bias current
range, make the MAX3646 ideal for driving FP/DFB
lasers in fiber optic modules. External resistors set the
required laser current levels. The MAX3646 provides
transmit disable control (TX_DISABLE), single-point
fault tolerance, bias-current monitoring, and photocur-
rent 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 MAX3646 is
compliant with the SFF-8472 transmitter diagnostic and
SFP MSA timing requirements.
The MAX3646 is offered in a 4mm x 4mm, 24-pin thin
QFN package and operates over the extended -40°C to
+85°C temperature range.
Ordering Information
PART
MAX3646ETG
MAX3646ETG-T
MAX3646ETG+
MAX3646ETG+T
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 Thin QFN-EP*
24 Thin QFN-EP*
24 Thin QFN-EP*
24 Thin QFN-EP*
+Denotes
a lead-free/RoHS-compliant package.
*EP
= Exposed pad.
T = Tape and reel.
Pin Configuration
TH_TEMP
APCFILT2
20
APCFILT1
19
18 MD
17 V
CC
16 OUT+
15 OUT-
14 V
CC
*EP
7
PC_MON
8
BC_MON
9
SHUTDOWN
10
GND
11
TX_FAULT
12
GND
13 BIAS
MODSET
22
APCSET
21
TOP VIEW
MODBCOMP
23
Applications
Multirate OC-3 to OC-12 FEC Transceivers
125Mbps Ethernet SFP, GBIC, and 1 x 9
Transceivers
MODTCOMP 1
V
CC
2
IN+ 3
IN- 4
24
MAX3646
Typical Application Circuit appears at end of data sheet.
V
CC
5
TX_DISABLE 6
*THE EXPOSED PADDLE MUST BE SOLDERED TO SUPPLY
GROUND ON THE CIRCUIT BOARD.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
MAX3646
ABSOLUTE MAXIMUM RATINGS
Supply Voltage V
CC
...............................................-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
= +70°C)
24-Pin TQFN (derate 27.8mW/°C above +70°C) .......2222mW
Operating Junction Temperature Range ...........-55°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow)
Lead (Pb)-free packages..............................................+260°C
Packages containing lead (Pb).....................................+240°C
Storage Temperature Range .............................-55°C to +150°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
(V
CC
= +2.97V to +3.63V, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V, I
BIAS
= 60mA, I
MOD
= 60mA, T
A
= +25°C, unless
otherwise noted.) (Notes 1, 2)
PARAMETER
POWER SUPPLY
Supply Current
Power-Supply Noise Rejection
I/O SPECIFICATIONS
Differential Input Swing
Common-Mode Input
LASER BIAS
Bias-Current-Setting Range
Bias Off Current
Bias-Current Monitor Ratio
LASER MODULATION
Modulation Current-Setting
Range
Output Edge Speed
Output Overshoot/Undershoot
Random Jitter
Deterministic Jitter (Notes 6, 8)
Modulation-Current Temperature
Stability
Modulation-Current-Setting Error
Modulation Off Current
I
MOD
(Note 5)
20% to 80%
(Notes 6, 7)
(Note 7)
(Notes 6, 7)
622Mbps, 5mA
≤
I
MOD
≤
85mA
155Mbps, 5mA
≤
I
MOD
≤
85mA
(Note 6)
15Ω load,
T
A
= +25°C
5mA
≤
I
MOD
≤
10mA
10mA < I
MOD
≤
85mA
5mA
≤
I
MOD
≤
10mA
10mA < I
MOD
≤
85mA
5mA
≤
I
MOD
≤
85mA
5
100
±6
1.1
24
45
±175
±125
2.5
46
100
±600
±480
±20
±15
0.1
85
200
mA
ps
%
ps
RMS
ps
P-P
ppm/°C
%
mA
TX_DISABLE = high
I
BIAS
/ I
BC_MON
62
76
1
100
0.1
90
mA
mA
mA/mA
V
ID
V
CM
DC-coupled, Figure 1
0.2
1.7
2.4
V
CC
-
V
ID
/ 4
V
P-P
V
I
CC
PSNR
(Note 3)
f
≤
1MHz, 100mA
P-P
(Note 4)
47
33
60
mA
dB
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
TX_DISABLE = high
2
_______________________________________________________________________________________
155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= +2.97V to +3.63V, T
A
= -40°C to +85°C. Typical values are at V
CC
= +3.3V, I
BIAS
= 60mA, I
MOD
= 60mA, T
A
= +25°C, unless
otherwise noted.) (Notes 1, 2)
PARAMETER
Monitor-Diode Input Current
Range
MD Pin Voltage
MD Current Monitor Ratio
APC Loop Time Constant
APC Setting Stability
APC Setting Accuracy
I
MOD
Compensation-Setting
Range by Bias
I
MOD
Compensation-Setting
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
INTERFACE SIGNALS
TX_DISABLE Input High
TX_DISABLE Input Low
TX_DISABLE Input Current
TX_FAULT Output Low
Shutdown Output High
Shutdown Output Low
V
HI
V
LO
R
PULL
= 45kΩ (typical)
V
HI
= V
CC
V
LO
= GND
Sinking 1mA, open collector
Sourcing 100µA
Sinking 100µA
V
CC
- 0.4
0.4
-70
2.0
0.8
15
-140
0.4
V
V
µA
V
V
V
V
REF
C
APC_FILT
= 0.01µF,
ΔI
MD
/
ΔI
BIAS
= 1/80
(Note 6)
C
APC_FILT
= 0.01µF,
ΔI
MD
/
ΔI
BIAS
= 1/80
(Note 6)
Figure 5
1.14
1.3
5
600
1.39
µs
µs
V
K
TC
T
TH
I
MD
/ I
PC_MON
C
APC_FILT
= 0.01µF,
ΔI
MD
/
ΔI
BIAS
= 1/70
(Note 6)
T
A
= +25°C
K =
ΔI
MOD
/
ΔI
BIAS
TC =
ΔI
MOD
/
ΔT
(Note 6)
(Note 6)
0
0
+10
0.85
0.93
3.3
±100
±480
±15
1.5
1.0
+60
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX3646
AUTOMATIC POWER AND EXTINCTION RATIO CONTROLS
I
MD
Average current into the MD pin
18
1500
1.4
1.15
µA
V
mA/mA
µs
ppm/°C
%
mA/mA
mA/°C
°C
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
AC characterization is performed using the circuit in Figure 2 using a PRBS 2
23
- 1 or equivalent pattern.
Specifications at -40°C are guaranteed by design and characterization.
Excluding I
BIAS
and I
MOD
. Input data is AC-coupled. TX_FAULT open, SHUTDOWN open.
Power-supply noise rejection (PSNR) = 20log
10
(V
noise (on VCC
) /
ΔV
OUT
). V
OUT
is the voltage across the 15Ω load when IN+
is high.
The minimum required voltage at the OUT+ and OUT- pins is +0.75V.
Guaranteed by design and characterization.
Tested with 00001111 pattern at 622Mbps.
DJ includes pulse-width distortion (PWD).
_______________________________________________________________________________________
3
155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
MAX3646
Typical Operating Characteristics
(V
CC
= +3.3V, C
APC
= 0.01µF, I
BIAS
= 20mA, I
MOD
= 30mA, T
A
= +25°C, unless otherwise noted.)
OPTICAL EYE DIAGRAM
(622.08Mbps, 2
7
- 1 PRBS, 467MHz FILTER)
MAX3646 toc01
OPTICAL EYE DIAGRAM
(155Mbps, 2
7
- 1 PRBS, 117MHz FILTER)
MAX3646 toc02
ELECTRICAL EYE DIAGRAM
(I
MOD
= 30mA, 622.08MHz, 2
7
- 1 PRBS)
MAX3646 toc03
1310nm FP LASER
r
e
= 8.2dB
1310nm FP LASER
r
e
= 8.2dB
2pF BETWEEN OUT+
AND OUT-
75mV/div
270ps/div
1ns/div
320ps/div
SUPPLY CURRENT (I
CC
) vs. TEMPERATURE
(EXCLUDES BIAS AND MODULATION CURRENTS)
MAX3646 toc04
BIAS-CURRENT MONITOR RATIO
vs. TEMPERATURE
88
86
I
BIAS
/I
BC_MON
(mA/mA)
84
82
80
78
76
74
72
MAX3646 toc05
PHOTOCURRENT MONITOR RATIO
vs. TEMPERATURE
1.15
I
MD
/I
PC_MON
(mA/mA)
1.10
1.05
1.00
0.95
0.90
0.85
0.80
MAX3646 toc06
60
55
SUPPLY CURRENT (mA)
50
45
2.97V
40
35
30
3.3V
3.63V
90
1.20
70
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
MODULATION CURRENT vs. R
MODSET
MAX3646 toc07
PHOTODIODE CURRENT vs. R
APCSET
MAX3646 toc08
DETERMINISTIC JITTER vs.
MODULATION CURRENT
155mbps
90
80
DJ (ps
P-P
)
70
60
50
MAX3646 toc09
90
80
70
60
I
MOD
(mA)
1.4
1.2
1.0
I
MD
(mA)
0.8
0.6
0.4
0.2
0
100
50
40
30
20
10
0
1
10
R
MODSET
(kΩ)
100
40
30
20
0.1
1
R
APCSET
(kΩ)
10
100
0
10
20
30
40
50
60
70
80
90
I
MOD
(mA)
4
_______________________________________________________________________________________
155Mbps to 622Mbps SFF/SFP
Laser Driver with Extinction Ratio Control
Typical Operating Characteristics (continued)
(V
CC
= +3.3V, C
APC
= 0.01µF, I
BIAS
= 20mA, I
MOD
= 30mA, T
A
= +25°C, unless otherwise noted.)
MAX3646
RANDOM JITTER vs.
MODULATION CURRENT
MAX3646 toc10
COMPENSATION (K) vs. R
MODBCOMP
MAX3646 toc11
TEMPERATURE COMPENSATION vs.
R
TH_TEMP
(R
MODTCOMP
= 500Ω)
MAX3646 toc12
MAX3646 toc15
2.0
1.8
1.6
1.4
RJ (ps
RMS
)
1.2
1.0
0.8
0.6
0.4
0.2
0
0
10
20
30
40
50
60
70
80
10
100
90
80
I
MOD
(mA)
R
TH_TEMP
= 7kΩ
70
60
50
40
R
TH_TEMP
= 4kΩ
R
TH_TEMP
= 2kΩ
R
TH_TEMP
= 12kΩ
1
K (mA/mA)
0.1
0.01
0.001
30
0.01
0.1
1
10
100
-10 0
10 20 30 40 50 60 70 80 90
TEMPERATURE (°C)
R
MODBCOMP
(kΩ)
90
I
MOD
(mA)
TEMPERATURE COMPENSATION vs.
R
TH_TEMP
(R
MODTCOMP
= 10kΩ)
MAX3646 toc13
HOT PLUG WITH TX_DISABLE LOW
MAX3646 toc14
TRANSMITTER ENABLE
V
CC
FAULT
HIGH
TX_DISABLE
t_on = 23.8μs
LOW
LASER
OUTPUT
3.3V
LOW
44
42
40
I
MOD
(mA)
38
36
34
32
30
R
TH_TEMP
= 12kΩ
R
TH_TEMP
= 7kΩ
R
TH_TEMP
= 4kΩ
R
TH_TEMP
= 2kΩ
3.3V
V
CC
0V
FAULT
TX_DISABLE
LOW
LASER
OUTPUT
LOW
t_init = 59.6ms
-10 0 10 20 30 40 50 60 70 80 90 100
TEMPERATURE (°C)
20ms/div
10μs/div
TRANSMITTER DISABLE
MAX37646 toc16
RESPONSE TO FAULT
MAX3646 toc17
FAULT RECOVERY TIME
MAX3646 toc18
V
CC
FAULT
3.3V
LOW
HIGH
V
PC_MON
EXTERNALLY
FORCED FAULT
t_fault = 160ns
V
PC_MON
EXTERNALLY
FORCED FAULT
FAULT
HIGH
FAULT
TX_DISABLE
TX_DISABLE
LOW
LASER
OUTPUT
t_init = 58ms
HIGH
LOW
LOW
TX_DISABLE
LOW
LASER
OUTPUT
91.2ns
LASER
OUTPUT
20ns/div
400ns/div
40ms/div
_______________________________________________________________________________________
5
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