MAXIM MAX3656 User Manual
General Description
The MAX3656 is a burst-mode laser driver that operates at data rates from 155Mbps up to 2.5Gbps. The
laser driver accepts either positive-referenced emittercoupled 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 singlesupply voltage as low as +3.0V.
A digital automatic power-control (APC) loop is provided
to maintain the average optical power over the full temperature 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 indicate when the APC loop can no longer maintain the
average power. The MAX3656 can be configured for
nonburst-mode applications (continuous mode) by connecting 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.
Applications
Fiber-to-the-Home (FTTH) and Fiber-to-theBusiness (FTTB) Broadband Access Systems
Passive Optical Network (PON) Transmitters
APON, EPON, and GPON Upstream Transmitters
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
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
SERIAL
DATA
SOURCE
IN+
IN-
BEN+
BEN-
V
CC
100Ω
100Ω
OUT-
APCSET
MODSET
BIASMAX
EN
GND
FAIL
LONGB
OUT+
BIAS+
BIAS-
MD
MAX3656
BURST
CONTROL
V
CC
V
CC
V
CC
Typical Application Circuit
19-2790; Rev 2; 10/04
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.
+ Denotes lead-free package.
*Dice are designed to operate from T
J
= -40°C to +120°C, but
are only tested and guaranteed at T
A
= +25°C.
**EP = Exposed pad.
Ordering Information
Functional Diagram appears at end of data sheet.
PART TEMP RANGE PIN-PACKAGE
MAX3656E/D — Dice* —
MAX3656ETG -40°C to +85°C 24 Thin QFN-EP** T2444-1
MAX3656ETG+ -40°C to +85°C 24 Thin QFN-EP** T2444-1
PKG
CODE
TOP VIEW
V
CC
IN+
IN-
V
CC
BEN+
BEN-
**EXPOSED PAD IS CONNECTED TO GND
MODSET
APCSET
1
2
3
4
5
6
MAX3656
7891011 12
CC
EN
V
GND
THIN QFN
GND
MD
VCCBIASMAX
192021222324
18
V
CC
17
OUT-
16
LONGB
OUT+
V
15
CC
14
BIAS+
BIAS-
13
FAIL
GND
MAX3656
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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
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-EP
(derate 27.8mW/°C above +85°C).............................1805mW
Operating Ambient Temperature
Range (T
A
).......................................................-40°C to +85°C
Operating Junction Temperature
Range (T
J
) .....................................................-55°C to +150°C
Storage Ambient Temperature
Range (T
STG
).................................................-55°C to +150°C
Processing Temperature (die) .........................................+400°C
Lead Temperature (soldering,10s) ..................................+300°C
OPERATING CONDITIONS
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:
where I
MD
, I
MOD
, and re(extinction ratio) are set externally.
Note 3: Operation outside this range degrades APC loop performance.
ELECTRICAL CHARACTERISTICS
(Typical values are at VCC= +3.3V, I
BIAS
= 20mA, I
MOD
= 25mA, extinction ratio = 10dB, and TA= +25°C, unless otherwise noted.)
Supply Voltage V
Supply Turn-On Time 10% to 90% 0.001 10 ms
Ambient Temperature -40 +85 °C
Data Mark Density Average 50 %
Consecutive Identical Digits CID 80 Bits
Data Rate 155 2500 Mbps
Monitor Diode Capacitance C
Laser-to-Monitor Diode Gain A
Extinction Ratio r
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
CC
For minimum burst on-time (Note 1) 15 pF
MD
∆ ( m oni tor cur r ent) /∆ ( l aser cur r ent ( ab ove I
LMD
( N otes 2, 3)
10 log (P1/P0) (Note 3) 8.2 12.0 dB
e
A
=
LMD
×
I
MOD
MD
e
rI
e
−2I r I
+
T H
3.0 3.3 3.6 V
) )
0.005 0.050 A/A
POWER SUPPLY
Power-Supply Current I
INPUT SPECIFICATIONS
Differential Input Voltage V
Common-Mode Input Voltage V
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
, V
I N
CC
CM
(Note 1) 40 70 mA
B E N
0.2 1.6 V
VCC -
1.49
VCC -
1.32
V
V
C C
IN
P-P
-
/4
V
MAX3656
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(Typical values are at VCC= +3.3V, I
BIAS
= 20mA, I
MOD
= 25mA, extinction ratio = 10dB, and TA= +25°C, unless otherwise noted.)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Single-Ended Input Voltage
EN Input High Voltage V
EN Input Low Voltage V
FAIL Output High Voltage V
FAIL Output Low Voltage V
V
BEN+
V
BEN-
,
IH
IL
S our ci ng 50µA, VCC = 3.0V 2.4 V
OH
S i nki ng 100µA, V CC = 3.6V 0.4 V
OL
0.8 V
2.0 V
0.8 V
BIAS GENERATOR
Bias-On Current Range I
Bias-Off Current Range I
BIAS
BIAS-OFF
Bias-Current Temperature
Stability
Bias-Current Absolute Accuracy APC open-loop I
Voltage at BIAS pin ≥ 0.6V 1 70 mA
EN = high or BEN = low, V
I
APC open loop
BIAS
I
BIAS
> 20mA (Note 3) -15 +15 %
BIAS
≤ 2.6V (Note 2) 5 100 µA
BIAS
= 70mA 148
= 15mA 98
ppm/°C
BIAS M AX C ur r ent- S etti ng Rang e1570mA
APC LOOP
MD Reverse-Bias Voltage V
MD Bias-Setting Stability
(Note 4)
MD Bias-Setting Accuracy
(Note 3)
MD DC-Current Range I
MD
With respect to V
CC
1.6 V
IMD = 50µA -750 +750
= 1500µA -480 +480
I
MD
IMD = 50µA -25 +25
= 1500µA -15 +15
I
MD
Average current into MD pin 50 1500 µA
MD
ppm/°C
%
Case 1 (Note 5) (LONGB = 0) 12
APC Loop Initialization Time
(Note 4)
t
INIT
Case 2 (Note 6) (LONGB = 0) 2.12
µs
Case 3 (Note 7) (LONGB = 0) 1.60 1.92
LASER MODULATOR
Modulation ON Current Range I
Modulation OFF Current I
MOD
MOD-OFF
Data rate ≤1.25Gbps 10 85
Data rate >1.25Gbps 10 60
mA
EN = high or BEN = low, IN = low (Note 2) 16 150 µA
Modulation-Current Stability (Note 13) -480 +480 ppm/°C
Modulation-Current Absolute
Accuracy
Instantaneous Voltage at
Modulator Output (OUT+)
Modulation-Current Rise Time t
Modulation-Current Fall Time t
R
F
> 15mA (Note 3) -15 +15 %
I
MOD
10mA ≤ I
60mA ≤ I
10mA ≤ I
10mA ≤ I
< 60mA 0.6
MOD
≤ 85mA 0.75
MOD
≤ 85mA (Notes 8, 13) 40 85 ps
MOD
≤ 85mA (Notes 8, 13) 40 85 ps
MOD
V
Output Over-/Undershoot 20 %
Deterministic Jitter
(Notes 9, 13)
DJ
155Mbps to 1.25Gbps, 10mA ≤ I
1.25Gbps to 2.5Gbps, 10mA ≤ I
Random Jitter RJ (Note 13) 0.8 1.4 ps
≤ 85mA 17 45
MOD
≤ 60mA 17 40
MOD
ps
P-P
RMS
MAX3656
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(Typical values are at VCC= +3.3V, I
BIAS
= 20mA, I
MOD
= 25mA, extinction ratio = 10dB, and TA= +25°C, unless otherwise noted.)
Note 1: Excludes I
BIAS
and I
MOD
. Maximum value is specified at I
MOD
= 85mA, I
BIAS
= 70mA, and IMD= 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 ≤ VCC≤ 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 IMD= 1500µA) within 12µs from the time that VCC≥ 3.0V.
Note 6: I
BIAS
error is less than 3.8mA (for an extinction ratio of 10dB and IMD= 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 IMD= 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 translates 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 + 27- 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.
BURST-MODE SPECIFICATIONS
Burst Enable Delay APC closed loop (Notes 10, 11, 13) 2.3 ns
Burst Disable Delay APC closed loop (Notes 10, 12, 13) 2.0 ns
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
OPTICAL EVALUATION
Optical Eye Diagram Mask
Margin
B-ON
B-OFF
155Mbps 2881
622Mbps 720Burst On-Time (Note 13) t
1.25Gbps, 2.5Gbps 576
155Mbps 192
622Mbps 96Burst Off-Time (Note 13) t
1.25Gbps, 2.5Gbps 96
E xceLi g ht
S LT3120- D N
l aser d i od e
( or eq ui val ent)
155.52Mbps 42
622.08Mbps 30
1.25Gbps 23
2.48832Gbps 18
ns
ns
%
MAX3656
155Mbps to 2.5Gbps Burst-Mode
Laser Driver
_______________________________________________________________________________________ 5
Figure 1. Enable and Disable Delay Times
Figure 2. Output Termination for Characterization
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
OPTICAL EYE DIAGRAM
(155.52Mbps, 117MHz FILTER,
PATTERN = PRBS 2
7
- 1 + 80 CID)
MAX3656 toc01
EXCELIGHT SLT3120-DN LASER
AVERAGE OPTICAL POWER = -4dBm
EXTINCTION RATIO = 15.2dB
MASK MARGIN = 42%
OPTICAL EYE DIAGRAM
(622.08Mbps, 467MHz FILTER,
PATTERN = PRBS 2
7
- 1 + 80 CID)
MAX3656 toc02
EXCELIGHT SLT3120-DN LASER
AVERAGE POWER = -4dBm
EXTINCTION RATIO = 15.1dB
MASK MARGIN = 30%
OPTICAL EYE DIAGRAM
(1.25Gbps, 933MHz FILTER,
PATTERN = PRBS 2
7
- 1 + 80 CID)
MAX3656 toc03
EXCELIGHT SLT3120-DN LASER
AVERAGE POWER = -3.5dBm
EXTINCTION RATIO = 14dB
MASK MARGIN = 23%
V
CC
BEN+
BEN-
I
BIAS
+
I
MOD
ENABLE DELAY
10% OF I
BEN ±MIDPOINT
BIAS
DISABLE DELAY
I
FINAL
I
I
FINAL
FINAL
× 110%
× 90%
22.1Ω
OUT-
49.9Ω
V
CC
MAX3656
22.1Ω
26.7Ω
121Ω
Z0 = 50Ω
= 50Ω
Z
0
V
CC
V
CC
OSCILLOSCOPE
26.7Ω
35.7Ω
OUT+
BIAS+
BIAS-
I
MOD
I
BIAS
50Ω
50Ω
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