19-2790; Rev 4; 9/10
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
General Description
The MAX3656 is a burst-mode laser driver that oper-
ates at data rates from 155Mbps up to 2.5Gbps. The
laser driver accepts either positive-referenced emitter-
coupled logic (PECL) or current-mode logic (CML) data
inputs and provides bias and modulation current for the
laser diode. The device can switch the laser diode from
a completely dark (off) condition to a full (on) condition
(with proper bias and modulation currents) in less than
2ns. The MAX3656 incorporates DC-coupling between
laser driver and laser diode and operates with a single-
supply voltage as low as +3.0V.
A digital automatic power-control (APC) loop is provided
to maintain the average optical power over the full tem-
perature range and lifetime. The APC loop is functional
for a minimum burst on-time of 576ns and minimum
burst off-time of 96ns, with no limit on the maximum
burst on- or off-time. A fail monitor is provided to indi-
cate when the APC loop can no longer maintain the
average power. The MAX3656 can be configured for
nonburst-mode applications (continuous mode) by con-
necting burst enable (BEN) high. For power saving, the
MAX3656 provides enabling and disabling functionality.
The modulation current can be set from 10mA to 85mA
and the bias current can be set from 1mA to 70mA.
The MAX3656 is packaged in a small, 24-pin, 4mm
✕
4mm thin QFN package and consumes only 132mW
(typ), excluding bias and modulation currents.
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
Features
Multirate Operation from 155Mbps to 2.5Gbps
Burst Enable/Disable Delay <2ns
Burst On-Time of 576ns to Infinity
Infinite Bias-Current Hold Time Between Bursts
DC-Coupled Operation with Single +3.3V Power
Supply
40mA Typical Supply Current
Programmable Bias Current from 1mA to 70mA
Programmable Modulation Current from 10mA
to 85mA
Automatic Average Power Control with Failure
Monitor (No C
APC
Capacitor Needed)
APC Loop Initialization ≤3 Bursts
MAX3656
Ordering Information
PART
MAX3656ETG
MAX3656ETG+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
24 Thin QFN-EP*
24 Thin QFN-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
Functional Diagram appears at end of data sheet.
Applications
Fiber-to-the-Home (FTTH) and Fiber-to-the-
Business (FTTB) Broadband Access Systems
Passive Optical Network (PON) Transmitters
APON, EPON, and GPON Upstream Transmitters
Typical Application Circuit
+3.3V
+3.3V
+3.3V
10Ω
130Ω
SERIAL
DATA
SOURCE
82Ω
82Ω
130Ω
APCSET
MODSET
IN+
IN-
BIASMAX
10nH
V
CC
Pin Configuration
BIASMAX
MODSET
APCSET
GND
V
CC
MD
15Ω
OUT-
5.6Ω
OUT+
TOP VIEW
24
V
CC
IN+
IN-
V
CC
BEN+
BEN-
1
2
3
4
5
23
22
21
20
19
18
17
16
V
CC
MAX3656
OUT-
5.6Ω
BIAS+
75Ω
27pF
+3.3V
OUT+
10Ω
+3.3V
MAX3656
15
14
*EP
13
V
CC
BIAS+
BIAS-
130Ω
BURST
CONTROL
82Ω
130Ω
BEN+
LONGB
GND
FAIL
BEN-
82Ω
EN
BIAS-
6
7
EN
8
GND
9
V
CC
10
FAIL
11
GND
12
LONGB
MD
THIN QFN
*EXPOSED PAD IS CONNECTED TO GND
________________________________________________________________
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 2.5Gbps Burst-Mode
Laser Driver
MAX3656
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
..............................................-0.5V to +6.0V
Current into BIAS+, BIAS-, OUT+, OUT- ........-20mA to +150mA
Current into MD.................................................... -5mA to +5mA
Current into
FAIL
...............................................-10mA to +10mA
Voltage at IN+, IN-, BEN+, BEN-,
EN,
LONGB ...................................................-0.5V to (V
CC
+ 0.5V)
Voltage at MODSET, APCSET, BIASMAX .............-0.5V to +3.0V
Voltage at OUT+, OUT-.............................+0.5V to (V
CC
+ 1.5V)
Voltage at BIAS+, BIAS-............................+0.5V to (V
CC
+ 0.5V)
Continuous Power Dissipation (T
A
= +85°C)
24-Lead Thin QFN
(derate 27.8mW/°C above +85°C) .............................1805mW
Operating Ambient Temperature Range (T
A
)......-40°C to +85°C
Storage Ambient Temperature Range (T
STG
) ...-55°C to +150°C
Lead Temperature (soldering,10s) ..................................+300°C
Soldering Temperature (reflow)
Lead(Pb)-free...............................................................+260°C
Containing lead(Pb) .....................................................+240°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.
OPERATING CONDITIONS
PARAMETER
Supply Voltage
Supply Turn-On Time
Ambient Temperature
Data Mark Density
Consecutive Identical Digits
Data Rate
Monitor Diode Capacitance
Laser-to-Monitor Diode Gain
Extinction Ratio
C
MD
A
LMD
r
e
For minimum burst on-time (Note 1)
Δ
(monitor current)/Δ (laser current (above I
TH
))
(Notes 2, 3)
10 log (P
1
/P
0
) (Note 3)
0.005
8.2
CID
155
Average
SYMBOL
V
CC
10% to 90%
CONDITIONS
MIN
3.0
0.001
-40
50
80
2500
15
0.050
12.0
TYP
3.3
MAX
3.6
10
+85
UNITS
V
ms
°C
%
Bits
Mbps
pF
A/A
dB
Note 1:
Larger MD capacitance increases the minimum burst on-time.
Note 2:
Laser-to-monitor gain equals the laser slope efficiency multiplied by the photodiode responsivity multiplied by the losses due
to laser-to-monitor diode coupling (A
LMD
=
η
LASER
✕
ρ
MONITORDIODE
✕
L
LASER-TO-MONITORDIODE
).
where L = laser-to-monitor diode coupling loss. A
LMD
can also be calculated by:
⎛
2
×
I
⎞ ⎛
r
−
I
⎞
MD
e
A
LMD
= ⎜
⎟ ⎜
⎟
⎝
I
MOD
⎠ ⎝
r
e
+
I
⎠
where I
MD
, I
MOD
, and r
e
(extinction ratio) are set externally.
Note 3:
Operation outside this range degrades APC loop performance.
ELECTRICAL CHARACTERISTICS
(Typical values are at V
CC
= +3.3V, I
BIAS
= 20mA, I
MOD
= 25mA, extinction ratio = 10dB, and T
A
= +25°C, unless otherwise noted.)
PARAMETER
POWER SUPPLY
Power-Supply Current
INPUT SPECIFICATIONS
Differential Input Voltage
Common-Mode Input Voltage
V
IN
, V
BEN
V
CM
0.2
V
CC
-
1.49
V
CC
-
1.32
1.6
V
CC
-
V
IN
/4
V
P-P
V
I
CC
(Note 1)
40
70
mA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
ELECTRICAL CHARACTERISTICS (continued)
(Typical values are at V
CC
= +3.3V, I
BIAS
= 20mA, I
MOD
= 25mA, extinction ratio = 10dB, and T
A
= +25°C, unless otherwise noted.)
PARAMETER
Single-Ended Input Voltage
EN
Input High Voltage
EN
Input Low Voltage
FAIL
Output High Voltage
FAIL
Output Low Voltage
BIAS GENERATOR
Bias-On Current Range
Bias-Off Current Range
Bias-Current Temperature
Stability
Bias-Current Absolute
Accuracy
BIASMAX Current-Setting Range
APC LOOP
MD Reverse-Bias Voltage
MD Bias-Setting Stability
(Note 4)
MD Bias-Setting Accuracy
(Note 3)
MD DC-Current Range
APC Loop Initialization Time
(Note 4)
LASER MODULATOR
Modulation ON Current Range
Modulation OFF Current
Modulation-Current Stability
Modulation-Current Absolute
Accuracy
Instantaneous Voltage at
Modulator Output (OUT+)
Modulation-Current Rise Time
Modulation-Current Fall Time
Output Over-/Undershoot
Deterministic Jitter
(Notes 9, 13)
Random Jitter
DJ
RJ
155Mbps to 1.25Gbps, 10mA
1.25Gbps to 2.5Gbps, 10mA
(Note 13)
I
MOD
I
MOD
85mA
60mA
t
R
t
F
I
MOD
Data rate 1.25Gbps
Data rate >1.25Gbps
(Note 13)
I
MOD
> 15mA (Note 3)
10mA
60mA
10mA
10mA
I
MOD
< 60mA
I
MOD
I
MOD
I
MOD
85mA
85mA (Notes 8, 13)
85mA (Notes 8, 13)
10
10
16
-480
-15
0.6
0.75
40
40
20
17
17
0.8
45
40
1.4
85
85
85
60
150
+480
+15
mA
μA
ppm/°C
%
V
ps
ps
%
ps
P-P
ps
RMS
I
MD
t
INIT
V
MD
With respect to V
CC
I
MD
= 50μA
I
MD
= 1500μA
I
MD
= 50μA
I
MD
= 1500μA
Average current into MD pin
Case 1 (Note 5) (LONGB = 0)
Case 2 (Note 6) (LONGB = 0)
Case 3 (Note 7) (LONGB = 0)
1.6
-750
-480
-25
-15
50
12
2.12
1.60
1.92
μs
+750
+480
+25
+15
1500
V
ppm/°C
%
μA
I
BIAS
Voltage at BIAS pin 0.6V
2.6V (Note 2)
I
BIAS
= 70mA
I
BIAS
= 15mA
-15
15
1
5
148
98
+15
70
70
100
mA
μA
ppm/°C
%
mA
I
BIAS-OFF
EN
= high or BEN = low, V
BIAS
APC open loop
SYMBOL
V
BEN+
,
V
BEN-
V
IH
V
IL
V
OH
V
OL
Sourcing 50μA, V
CC
= 3.0V
Sinking 100μA, V
CC
= 3.6V
2.4
0.4
2.0
0.8
CONDITIONS
MIN
TYP
0.8
MAX
UNITS
V
V
V
V
V
MAX3656
APC open-loop I
BIAS
> 20mA (Note 3)
I
MOD-OFF
EN
= high or BEN = low, IN = low (Note 2)
_______________________________________________________________________________________
3
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
MAX3656
ELECTRICAL CHARACTERISTICS (continued)
(Typical values are at V
CC
= +3.3V, I
BIAS
= 20mA, I
MOD
= 25mA, extinction ratio = 10dB, and T
A
= +25°C, unless otherwise noted.)
PARAMETER
Burst Enable Delay
Burst Disable Delay
Burst On-Time (Note 13)
t
B-ON
SYMBOL
CONDITIONS
APC closed loop (Notes 10, 11, 13)
APC closed loop (Notes 10, 12, 13)
155Mbps
622Mbps
1.25Gbps, 2.5Gbps
155Mbps
Burst Off-Time (Note 13)
OPTICAL EVALUATION
Optical Eye Diagram Mask
Margin
ExceLight
SLT2886-LR
laser diode
(or equivalent)
155.52Mbps
622.08Mbps
1.24416Gbps
2.48832Gbps
45
40
31
24
%
t
B-OFF
622Mbps
1.25Gbps, 2.5Gbps
2881
720
576
192
96
96
ns
ns
MIN
TYP
MAX
2.3
2.0
UNITS
ns
ns
BURST-MODE SPECIFICATIONS
Note 1:
Excludes I
BIAS
and I
MOD
. Maximum value is specified at I
MOD
= 85mA, I
BIAS
= 70mA, and I
MD
= 1.5mA.
Note 2:
For safety purposes, both the bias and modulation currents are switched off if any of the current set pins (BIASMAX, MODSET)
are grounded.
Note 3:
Accuracy refers to part-to-part variation.
Note 4:
APC loop initialization definitions:
I
BIAS
Error:
I
BIAS
- I
BIASSET
, where I
BIAS
= the actual bias current and I
BIASSET
= the level of bias current set by the R
APCSET
resistor.
Initialization Case 1: Continuous Mode Power-Up.
In this case,
EN
= low, BEN = high, and then V
CC
is ramped up from
0V to
≥3.0V.
Initialization Case 2: Chip-Enable Reset.
In this case, 3.0V
≤
V
CC
≤
3.6V, BEN = high, and then
EN
changes from high to low.
Initialization Case 3: Burst-Mode Startup.
In this case, 3.0V
≤
V
CC
≤
3.6V,
EN
= low, and then BEN changes from low to high.
Note 5:
I
BIAS
error is less than 3.8mA (for an extinction ratio of 10dB and I
MD
= 1500µA) within 12µs from the time that V
CC
≥
3.0V.
Note 6:
I
BIAS
error is less than 3.8mA (for an extinction ratio of 10dB and I
MD
= 1500µA) within 2.1µs (typ) from the time that
EN
< 0.8V.
Note 7:
I
BIAS
error must be less than 3.8mA (for an extinction ratio of 10dB and I
MD
= 1500µA) at or before the end of the third
burst following the transition of BEN from low to high. For the shortest burst on- and off-time (576ns and 96ns), this trans-
lates to 1.92µs from when BEN toggles from low to high for the first time after startup.
Note 8:
Rise and fall times are measured as 20% to 80% of the output amplitude with a repeating 0000011111.
Note 9:
Deterministic jitter is measured with a continuous data pattern (no bursting) of 2
7
- 1 PRBS + 80 consecutive ones + 2
7
- 1
PRBS + 80 consecutive zeros.
Note 10:
Measured electrically with a resistive load matched to the laser driver output.
Note 11:
Enable delay is measured between (1) the time at which the rising edge of the differential burst enable input signal reach-
es the midpoint of the voltage swing, and (2) the time at which the combined output currents (bias and modulation) reach
90% of the final level set by R
APCSET
, R
BIASMAX
, and R
MODSET
(after all transients such as overshoot, ringing, etc., have
settled to within 10% of their final values). See Figure 1. Measurement done for 10mA
≤
I
MOD
≤
85mA and 4mA
≤
I
BIAS
≤
70mA.
Note 12:
Disable delay is measured between (1) the time at which the falling edge of the differential burst enable input signal reaches
the midpoint of the voltage swing, and (2) the time at which the combined output currents (bias and modulation) fall below
10% of the bias on current (after transients have settled). See Figure 1. Measurement done for 10mA
≤
I
MOD
≤
85mA and
4mA
≤
I
BIAS
≤
70mA.
Note 13:
Guaranteed by design and characterization.
4
_______________________________________________________________________________________
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
MAX3656
V
CC
22.1Ω
BEN+
BEN-
I
BIAS
+
I
MOD
ENABLE DELAY
BEN
±MIDPOINT
I
FINAL
×
110%
I
FINAL
I
FINAL
×
90%
10% OF I
BIAS
OUT-
49.9Ω V
CC
MAX3656
22.1Ω
I
MOD
OSCILLOSCOPE
Z
0
= 50Ω
V
CC
50Ω
26.7Ω
I
BIAS
OUT+
DISABLE DELAY
Figure 1. Enable and Disable Delay Times
BIAS+
121Ω
BIAS-
Z
0
= 50Ω
V
CC
26.7Ω
50Ω
35.7Ω
Figure 2. Output Termination for Characterization
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
OPTICAL EYE DIAGRAM
(155.52Mbps, 117MHz FILTER,
PATTERN = 2
23
- 1 PRBS)
MAX3656 toc01
OPTICAL EYE DIAGRAM
(622.08Mbps, 467MHz FILTER,
PATTERN = 2
23
- 1 PRBS)
MAX3656 toc02
OPTICAL EYE DIAGRAM
(1.24416Gbps, 933MHz FILTER,
PATTERN = 2
23
- 1 PRBS)
MAX3656 toc03
EXCELIGHT SLT2886-LR LASER
AVERAGE OPTICAL POWER = -6dBm
EXTINCTION RATIO = 15dB
MASK MARGIN = 45%
EXCELIGHT SLT2886-LR LASER
AVERAGE OPTICAL POWER = -6dBm
EXTINCTION RATIO = 15dB
MASK MARGIN = 40%
EXCELIGHT SLT2886-LR LASER
AVERAGE OPTICAL POWER = -6dBm
EXTINCTION RATIO = 12dB
MASK MARGIN = 31%
_______________________________________________________________________________________
5
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