19-4799; Rev 4; 2/05
+3.3V, 622Mbps SDH/SONET
Laser Driver with Automatic Power Control
General Description
The MAX3668 is a complete, +3.3V laser driver with
automatic power control (APC) circuitry for SDH/SONET
applications up to 622Mbps. It accepts differential
PECL inputs, provides bias and modulation currents,
and operates over a temperature range of -40°C to
+85°C.
An APC feedback loop is incorporated to maintain a
constant average optical power over temperature and
lifetime. The wide modulation current range of 5mA to
75mA and bias current of 1mA to 80mA are easy to
program, making this product ideal for use in various
SDH/SONET applications.
The MAX3668 also provides enable control and a failure-
monitor output to indicate when the APC loop is unable
to maintain the average optical power. The MAX3668 is
available in a 5mm 32-pin TQFP package as well as in
dice.
♦
Single +3.3V or +5.0V Operation
♦
38mA Supply Current at +3.3V
♦
Programmable Modulation Current from
5mA to 75mA
♦
Programmable Bias Current from 1mA to 80mA
♦
Rise/Fall Time <200ps
♦
Automatic Average Power Control with Failure
Monitor
♦
Complies with ANSI, ITU, and Bellcore
SONET/SDH Specifications
♦
Enable Control
Features
MAX3668
†
Ordering Information
PART
MAX3668EHJ
MAX3668EHJ+
MAX3668E/D
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
Note
PIN-PACKAGE
32 TQFP (5mm x 5mm)
32 TQFP (5mm x 5mm)
Dice*
Applications
622Mbps SDH/SONET Access Nodes
Laser Driver Transmitters
Section Regenerators
Note:
Dice are designed to operate over a -40°C to +140°C
junction temperature (Tj) range, but are tested and guaranteed
at T
A
= +25°C.
*Contact
factory for availability.
+Denotes lead-free package.
Pin Configuration appears at end of data sheet.
Typical Operating Circuit
+3.3V
+3.3V
LASER
ENABLE
FAIL
V
CC
R-
6.3Ω
OUT-
OUT+
R+
20Ω
R
D
5Ω
C
D
1.0µF
130Ω
130Ω
DATA+
MAX3693
4:1
SERIALIZER
WITH
CLOCK GEN
PECL
DATA-
MAX3668
82Ω
82Ω
R
FILT
20Ω
C
FILT
5pF
BIASMAX
MODSET
APCSET
BIAS
CAPC
GND
MD
FERRITE
BEAD
C
MD
1000pF
0.1µF
†
C0
________________________________________________________________
Maxim Integrated Products
1
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.
+3.3V, 622Mbps SDH/SONET
Laser Driver with Automatic Power Control
MAX3668
ABSOLUTE MAXIMUM RATINGS
Supply Voltage, V
CC
.............................................-0.5V to +7.0V
Current into BIAS ............................................-20mA to +150mA
Current into OUT+, OUT- ............................... -20mA to +100mA
Current into MD....................................................-5mA to +5mA
Voltage at DATA+, DATA-, ENABLE,
FAIL
.......................................................-0.5V to (V
CC
+ 0.5V)
Voltage at OUT+, OUT- .............................+1.5V to (V
CC
+ 1.5V)
Voltage at MODSET, APCSET, BIASMAX,
CAPC............................................................... -0.5V to +3.0V
Voltage at BIAS .........................................+1.0V to (V
CC
+ 0.5V)
Continuous Power Dissipation (T
A
= +85°C)
32-Pin TQFP (derate 14.3mW/°C above +85°C)........ 929mW
Operating Junction Temperature Range ...........-55°C to +150°C
Processing Temperature (Die).........................................+400°C
Storage Temperature Range ........................... -65°C to +165°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.
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.14V to +5.5V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
= +3.3V, T
A
= +25°C.) (Note 1)
PARAMETER
Supply Current
Bias Current Range
Bias Off Current
Bias Current Stability
Bias Current Absolute Accuracy
Differential Input Voltage
Common-Mode Input Voltage
DATA+, DATA- Input Current
Monitor Diode Current Stability
Monitor Diode Current
Absolute Accuracy
DC Monitor Diode Current
Monitor Diode Input Voltage
(MD Pin)
TTL Input High Voltage
TTL Input Low Voltage
TTL Output High Voltage
(FAIL)
TTL Output Low Voltage
(FAIL)
I
MD
V
MD
V
IH
V
IL
V
OH
V
OL
Sourcing 50µA
Sinking 100µA
2.4
0.1
V
CC
- 0.3
2.0
0.8
V
CC
0.44
V
ID
V
ICM
I
IN
(Note 4)
I
MD
= 1mA
I
MD
= 18µA (Note 5)
-15
18
0.8
I
BIAS
SYMBOL
(Note 2)
V
BIAS
= V
CC
- 1.6V
ENABLE = low (Note 3)
APC open loop
APC open loop
Figure 1
PECL compatible
I
BIAS
= 80mA
I
BIAS
= 1mA
-15
200
V
CC
-
1.49
-1
-480
10
70
15
1000
V
CC
-
1.32
390
920
15
1600
V
CC
-
V
ID
/4
10
480
1
CONDITIONS
MIN
TYP
38
MAX
60
80
100
UNITS
mA
mA
µA
ppm/°C
%
mVp-p
V
µA
ppm/°C
%
µA
V
V
V
V
V
2
_______________________________________________________________________________________
+3.3V, 622Mbps SDH/SONET
Laser Driver with Automatic Power Control
MAX3668
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.14V to +5.5V, load as shown in Figure 2, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
CC
= +3.3V,
T
A
= +25°C.) (Note 6)
PARAMETER
Modulation Current Range
Modulation Off Current
Modulation Current Stability
Modulation Current Absolute
Accuracy
Output Rise/Fall Time
Jitter Generation (peak-to-peak)
Pulse-Width Distortion
(peak-to-peak)
Enable/Start-Up Delay
Maximum Consecutive Identical
Digits at 622Mbps
CID
t
R/
t
F
20% to 80%,
R
L
= 10Ω
| |
20Ω load
(Note 8)
(Notes 9, 10)
Open loop
80
I
MOD
= 5mA
I
MOD
= 75mA
70
10
250
I
MOD
= 5mA
I
MOD
= 75mA
SYMBOL
I
MOD
(Note 7)
ENABLE = low (Note 3)
I
MOD
= 75mA
I
MOD
= 5mA (Note 5)
-15
100
230
-620
175
300
15
200
375
100
155
135
CONDITIONS
MIN
5
TYP
MAX
75
200
620
UNITS
mA
µA
ppm/°C
%
ps
ps
ps
ns
Bits
Note 1:
Characteristics at -40°C are guaranteed by design and characterization. Dice are tested at T
A
= +25°C only.
Note 2:
Tested with R
MODSET
= 5.11kΩ (I
MOD
≈
38mA), R
BIASMAX
= 4.56kΩ (I
BIAS
≈
52mA), excluding I
BIAS
and I
MOD
.
Note 3:
Both the bias and modulation currents will be disabled if any of the current set pins are shorted to ground.
Note 4:
This assumes that the laser to monitor diode transfer function does not change with temperature.
Note 5:
See
Typical Operating Characteristics
for worst-case distributions.
Note 6:
AC characteristics are guaranteed by design and characterization.
Note 7:
Total I
MOD
out of OUT+. Refer to the
Design Procedure
for information regarding current delivered to the laser.
Note 8:
Input signal is a 622Mbps, 2
13
- 1 PRBS with 80 inserted zeros.
Note 9:
Input signal is a 622Mbps, 11110000 pattern.
Note 10:PWD
= (wider pulse – narrower pulse) / 2.
V
CC
DATA+
DATA-
(DATA+) -
(DATA-)
100mV MIN
800mV MAX
200mVp-p MIN
OUT-
20Ω
1.0µF
10Ω
1600mVp-p MAX
I
OUT
+
I
MOD
20Ω
MAX3668
OUT+
BIAS
1.0µF
OSCILLOSCOPE
12.4Ω
15Ω
V
CC
50Ω
Figure 1. Required Input Signal and Output Polarity
Figure 2. Output Termination for Characterization
3
_______________________________________________________________________________________
+3.3V, 622Mbps SDH/SONET
Laser Driver with Automatic Power Control
MAX3668
Typical Operating Characteristics
(V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.)
EYE DIAGRAM
(622Mbps, 1300nm LASER
WITH 467MHz FILTER)
MAX3668 TOC01
EYE DIAGRAM
(I
MOD
= 35mA)
MAX3668 TOC02
EYE DIAGRAM
(I
MOD
= 75mA)
622Mbps
MAX3668 TOC03
2
23
- 1 PRBS
622Mbps
PATTERN = 2
13
- 1 + 80 CID
I
MOD
= 35mA
PATTERN = 2
13
- 1 + 80 CID
I
MOD
= 75mA
193ps/div
200ps/div
200ps/div
MONITOR DIODE CURRENT
vs. APC SET RESISTOR
MAX3668 TOC04
BIAS CURRENT vs.
MAXIMUM BIAS SET RESISTOR
MAX3668 TOC05
MODULATION CURRENT
vs. MODULATION SET RESISTOR
MAX3688 TOC06
10
1000
100
1
I
BIAS
(mA)
I
MD
(mA)
100
I
MOD
(mA)
10
1
1
10
R
APCSET
(kΩ)
100
0.1
1
10
R
BIASMAX
(kΩ)
100
10
0.1
0.01
1
0.1
1
10
R
MODSET
(kΩ)
100
1000
RANDOM JITTER
vs. MODULATON CURRENT
MAX3668 TOC07
PULSE-WIDTH DISTORTION
vs. MODULATION CURRENT
45
40
35
PWD (ps)
MAX3668 TOC08
SUPPLY CURRENT
vs. TEMPERATURE
MAX3668 TOC09
21
INCLUDES RANDOM JITTER
DUE TO MEASUREMENT
EQUIPMENT
50
55
20
RANDOM JITTER (ps p-p)
50
SUPPLY CURRENT (mA)
V
CC
= +5.0V
45
V
CC
= +3.3V
40
19
30
25
20
15
18
17
10
5
35
I
BIAS
= 48mA
I
MOD
= 33mA
30
0
20
40
I
MOD
(mA)
60
80
-40
-15
10
35
60
85
TEMPERATURE (°C)
16
0
20
40
I
MOD
(mA)
60
80
0
4
_______________________________________________________________________________________
+3.3V, 622Mbps SDH/SONET
Laser Driver with Automatic Power Control
MAX3668
Typical Operating Characteristics (continued)
(V
CC
= +3.3V, T
A
= +25°C, unless otherwise noted.)
AVAILABLE BIAS CURRENT
vs. MAXIMUM BIAS SET RESISTOR
MAX3668 TOC10
DISTRIBUTION OF MODULATION CURRENT
STABILITY (WORST CASE)
MAX3668-11
DISTRIBUTION OF MONITOR DIODE CURRENT
STABILITY (WORST CASE)
T
A
= -40°C TO +85°C
I
MD
= 18µA
20
PERCENT OF UNITS (%)
MAX3668-12
1000
V
CC
= +3.3V, + 5V
100
BIAS CURRENT (mA)
25
T
A
= -40°C TO +85°C
I
MOD
= 5mA
20
PERCENT OF UNITS (%)
25
15
15
10
CLOSED-LOOP OPERATION
10
10
1
V
CC
= +3.3V
0.1
1.4
1.6
1.8
2.0
R
BIAS
(kΩ)
V
CC
= +5V
5
5
0
2.2
2.4
2.6
-25
65
155
245
335
425
515
MODULATION DIODE CURRENT STABILITY (ppm/°C)
0
-88
-52
20
92
160
MONITOR DIODE CURRENT STABILITY (ppm/°C)
Pin Description
PIN
1, 2, 6, 15,
17, 20, 24
3
4
5, 7, 8, 10,
14, 21, 22, 30
9
11
12, 13, 26,
27, 28
16
18
19
23
25
29
31
32
NAME
V
CC
DATA+
DATA-
GND
ENABLE
FAIL
N.C.
BIAS
OUT+
OUT-
MD
CAPC
APCSET
MODSET
BIASMAX
Positive Supply Voltage
Positive PECL Data Input
Negative PECL Data Input
Ground
TTL/CMOS Enable Input. High for normal operation, low to disable laser bias and modulation
currents. Internally pulled high.
TTL Output. Indicates APC failure when low. Internally pulled high through a 6kΩ resistor.
No Connection. Leave unconnected.
Laser Bias Current Output. Isolate from laser with a ferrite bead.
Positive Modulation Current Output. I
MOD
flows into this pad when the input signal is high.
Connect this pad to AC coupling network.
Negative Modulation Current Output. I
MOD
flows into this pad when the input signal is low.
Connect this pad to V
CC
through a 6.3Ω resistor.
Monitor Photodiode Connection. Connect this pad to the monitor photodiode anode. A capaci-
tor to ground is required to filter high-speed AC monitor photocurrent.
APC Compensation Capacitor. A 0.1µF capacitor connected from this pad to ground controls
the dominant pole of the automatic power control (APC) feedback loop.
APC Set Resistor. A resistor connected from this pad to ground sets the desired average opti-
cal power. The resulting current is equal to the desired DC monitor diode current. Connect a
100kΩ resistor from this pad to ground if APC is not used.
Modulation Set Resistor. A resistor from this pad to ground sets the laser modulation current.
Maximum Bias Set Resistor. A resistor from this pad to ground sets the maximum laser bias
current. The APC function can subtract from this maximum value but cannot add to it. This
resistor controls the bias-current level when the APC loop is not used.
5
FUNCTION
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