19-2194; Rev 1; 2/02
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
General Description
The MAX3996 is a high-speed laser driver for small-
form-factor (SFF) fiber optic LAN transmitters. It con-
tains a bias generator, a laser modulator, and
comprehensive safety features. Automatic power con-
trol (APC) adjusts the laser bias current to maintain
average optical power, regardless of changes in tem-
perature or laser properties. The driver accommodates
common anode or differential laser configurations. The
output current range of the MAX3996 is appropriate for
VCSELs and high-efficiency edge-emitting lasers.
The MAX3996 operates up to 3.2Gbps. It can switch up
to 30mA of laser modulation current and sink up to
60mA bias current. Adjustable temperature compensa-
tion is provided to keep the optical extinction ratio with-
in specifications over the operating temperature range.
The MAX3996 accommodates various laser packages,
including low-cost TO-46 headers. Low deterministic jit-
ter (9ps
P-P
), combined with fast edge transitions,
(65ps) provides excellent margins compared to indus-
try-standard transmitter eye masks.
This laser driver provides extensive safety features to
guarantee single-point fault tolerance. Safety features
include a transmit disable, redundant shutdown, and
laser-bias monitoring. The safety circuit detects faults
that could cause hazardous light levels and immediate-
ly disables the laser output. The MAX3996 safety cir-
cuits are compliant with SFF and small-form-factor
pluggable (SFP) multisource agreements (MSA).
The MAX3996 is available in a compact 4mm
✕
4mm,
20-pin QFN package and operates over a temperature
range of 0°C to +70°C.
o
9ps
P-P
Deterministic Jitter
o
20-Pin QFN 4mm
✕
4mm Package
o
3.0V to 5.5V Supply Voltage
o
Automatic Power Control
o
Integrated Safety Circuits
o
30mA Laser Modulation Current
o
Temperature Compensation of Modulation
Current
o
Compliant with SFF and SFP MSA
Features
MAX3996
Ordering Information
PART
MAX3996CGP
TEMP RANGE
0°C to +70°C
PIN-PACKAGE
20 QFN
Typical Application Circuit
V
CC
OPTIONAL SHUTDOWN
CIRCUITRY
V
CC
1.8kΩ
Applications
Fibre Channel Optical Transmitters
VCSEL Transmitters
Gigabit Ethernet Optical Transmitters
ATM LAN Optical Transmitters
10 Gigabit Ethernet WWDM
0.01µF
IN+
0.01µF
IN-
TX_DISABLE
V
CC
0.01µF
SHDNDRV
0.01µF
FAULT
OUT-
0.01µF
MAX3996
OUT+
L1*
25Ω
BIAS
Pin Configuration appears at end of data sheet.
PORDLY
MD
TC
C
PORDLY
R
TC
R
MOD
N.C.
C
COMP
R
SET
MODSET MON1 MON2 COMP
GND
*FERRITE BEAD
________________________________________________________________
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.
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
MAX3996
ABSOLUTE MAXIMUM RATINGS
Supply Voltage at V
CC
...........................................-0.5V to +7.0V
Voltage at TX_DISABLE, PORDLY, MON1, COMP,
IN+, IN-, MD, BIAS, MODSET, TC..........-0.5V to (V
CC
+ 0.5V)
Voltage between COMP and MON2 .....................................2.3V
Voltage between IN+ and IN- ..................................................5V
Voltage at OUT+, OUT- .........................(V
CC
- 2V) to (V
CC
+ 2V)
Voltage between MON1 and MON2 .....................................1.5V
Voltage between BIAS and MON2...........................................4V
Current into FAULT, SHDNDRV ..........................-1mA to +25mA
Current into OUT+, OUT- ....................................................60mA
Current into BIAS ..............................................................120mA
Continuous Power Dissipation (T
A
= +70°C)
20-Pin QFN (derate 20mW/°C)...................................1600mW
Operating Ambient Temperature Range .............-40°C to +85°C
Operating Junction Temperature Range. ..........-40°C to +150°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
= 3.0V to 5.5V, T
A
= 0°C to +70°C, unless otherwise noted. Typical values are at V
CC
= 3.3V, TC pin not connected, T
A
=
+25°C.) (Figure 1)
PARAMETER
Supply Current
Data Input Voltage Swing
TX_DISABLE Input Current
TX_DISABLE Input High Voltage
TX_DISABLE Input Low Voltage
FAULT Output High Voltage
FAULT Output Low Voltage
BIAS GENERATOR
Minimum Bias Current
Maximum Bias Current
MD Quiescent Voltage
Monitor Resistance
MD Input Current
BIAS Current During Fault
APC Time Constant
POWER-ON RESET (POR)
POR Threshold
POR Delay
POR Hysteresis
SHUTDOWN
I
SHDNDRV
= 10µA, FAULT = high
Voltage at SHDNDRV
LASER MODULATOR
Data Rate
< 3.2
Gbps
I
SHDNDRV
= 1mA, FAULT = low
I
SHDNDRV
= 15mA, FAULT = low
0
V
CC
- 0.4
V
CC
- 2.4
V
CC
- 1.2
V
t
PORDLY
Measured at V
CC
PORDLY = open (Note 3)
C
PORDLY
= 0.001µF (Note 3)
2.65
30
1.7
2.7
55
2.4
20
3.0
V
µs
ms
mV
I
BIAS_OFF
C
COMP
= 0.1µF
35
I
BIAS
I
BIAS
V
MD
R
MON
Current into BIAS pin
Current into BIAS pin
APC loop is closed
FAULT = high
TX_DISABLE = high
(Figure 4)
FAULT = low, TX_DISABLE = low
9.3
-3
60
1.04
1.12
V
CC
- 0.73
V
CC
- 0.73
11
0.8
12.7
3
10
Ω
µA
µA
µs
V
1
mA
mA
V
IH
V
IL
V
OH
V
OL
I
OH
= -100µA, 4.7kΩ < R
FAULT
< 10kΩ
I
OL
= 1mA
2.4
0.4
SYMBOL
I
CC
(Figure1)
(Note 1)
V
ID
CONDITIONS
V
CC
= 3.3V, I
MOD
= 15mA
V
CC
= 5.5V, I
MOD
= 30mA,
R
MODSET
= 2.37kΩ
Total differential signal (Figure 2)
0 < V
PIN
< V
CC
200
-100
2.0
0.8
MIN
TYP
47
52
75
2200
100
mA
MV
P-P
µA
V
V
V
V
MAX
UNITS
2
_______________________________________________________________________________________
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 3.0V to 5.5V, T
A
= 0°C to +70°C, unless otherwise noted. Typical values are at V
CC
= 3.3V, TC pin not connected, T
A
=
+25°C.) (Figure 1)
PARAMETER
Minimum Modulation Current
Maximum Modulation Current
Accuracy of Modulation Current
(Part-to-Part Variation)
Edge Transition Time
t
r
, t
f
SYMBOL
i
MOD
i
MOD
R
L
≤
25Ω
R
MODSET
= 2.37kΩ
(i
MOD
≈
30mAp-p into 25Ω)
i
MOD
= 5mA into 25Ω, 20% to 80% (Note 3)
i
MOD
= 10mA into 25Ω, 20% to 80% (Note 3)
i
MOD
= 30mA into 25Ω, 20% to 80% (Note 3)
i
MOD
= 5mA into 25Ω (Notes 2, 3)
Deterministic Jitter
Random Jitter
Modulation Current During Fault
Modulation Current Tempco
Input Resistance
Output Resistance
Input Common-Mode Voltage
SAFETY FEATURES
(See
Typical Operating Characteristics)
MODSET and TC Pin
Fault Threshold
BIAS Pin Fault Threshold
A fault will be triggered if V
BIAS
is less than
this voltage
A fault will be triggered if V
MON2
exceeds
this voltage
t_off
t_on
Time from rising edge of TX_DISABLE to
I
BIAS
= I
BIAS_OFF
and i
MOD
= i
MOD_OFF
(Note 3)
Time from falling edge of TX_DISABLE to
I
BIAS
and i
MOD
at 95% of steady state (Note 3)
From power ON or negation of FAULT using
TX_DISABLE. Time to set FAULT = low, i
MOD
=
95% of steady state and I
BIAS
= 95% of steady
state (Note 3)
Time from fault to FAULT = high, C
FAULT
< 20pF, R
FAULT
= 4.7kΩ (Note 3)
Time TX_DISABLE must be held high to
reset FAULT (Note 3)
200
300
400
mV
mV
R
IN
R
OUT
i
MOD_OFF
Tempco = MAX, R
MOD
= open
Tempco = MIN, R
TC
= open
Differential
Single ended; outputs to V
CC
85
42
50
V
CC
- 0.3
i
MOD
= 10mA into 25Ω (Notes 2, 3)
i
MOD
= 30mA into 25Ω (Notes 2, 3)
(Note 3)
30
-10
54
55
65
17
14
9
2
15
4000
50
115
58
40
+10
100
125
130
35
22
20
8
200
ps
RMS
µA
P-P
ppm/°C
Ω
Ω
V
ps
P-P
ps
CONDITIONS
MIN
TYP
MAX
2
UNITS
mA
P-P
mA
P-P
%
MAX3996
Excessive Bias Current Fault
TX Disable Time
TX Disable Negate Time
400
0.06
37
440
5
500
mV
µs
µs
Reset Initialization Time
t_init
23
200
ms
Fault Assert Time
TX_DISABLE Reset
t_fault
t_reset
14
0.01
50
1
µs
µs
Note 1:
Supply current excludes bias and modulation currents.
Note 2:
Deterministic jitter is the peak-to-peak deviation from the ideal time crossings measured with a K28.5 bit pattern
00111110101100000101.
Note 3:
AC characteristics guaranteed by design and characterization.
_______________________________________________________________________________________
3
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
MAX3996
Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
ELECTRICAL EYE DIAGRAM
(i
MOD
= 30mA, 2
7
- 1 PRBS, 2.5Gbps)
MAX3996 toc01
ELECTRICAL EYE DIAGRAM
(i
MOD
= 30mA, 2
7
- 1 PRBS, 3.2Gbps)
25Ω LOAD
MAX3996 toc02
OPTICAL EYE DIAGRAM
(i
MOD
= 5mA, 850nm VCSEL, 2
7
- 1 PRBS,
2.5Gbps, 1870MHz FILTER)
MAX3996 toc03
25Ω LOAD
120mV/
div
120mV/
div
64ps/div
52ps/div
57ps/div
OPTICAL EYE DIAGRAM
(i
MOD
= 15mA, 1310nm LASER, 2
7
- 1 PRBS,
2.5Gbps, 1870MHz FILTER)
MAX3996 toc04
TRANSITION TIME
vs. MODULATION CURRENT
MAX3996 toc05
DETERMINISTIC JITTER
vs. MODULATION CURRENT
MAX3996 toc06
80
70
TRANSITION TIME (ps)
60
50
40
30
20
FALL TIME
RISE TIME
30
DETERMINISTIC JITTER (ps
P-P
)
25
20
15
TOTAL DJ
10
PWD
5
0
57ps/div
5
10
15
20
i
MOD
(mA)
25
30
35
5
10
15
20
i
MOD
(mA)
25
30
35
SUPPLY CURRENT vs.
TEMPERATURE (i
MOD
= 15mA)
65
SUPPLY CURRENT (mA)
60
55
50
45
40
35
30
0
15
30
45
60
75
AMBIENT TEMPERATURE (°C)
10µ
10p
POR DELAY (s)
10m
EXCLUDES I
BIAS
, i
MOD
25Ω LOAD
MAX3996 toc07
POR DELAY vs. C
PORDLY
MAX3996 toc08
70
1
100m
1m
100µ
100p
1n
C
PORDLY
(F)
10n
100n
4
_______________________________________________________________________________________
3.0V to 5.5V, 2.5Gbps VCSEL
and Laser Driver
Typical Operating Characteristics (continued)
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
HOT PLUG WITH
TX_DISABLE LOW
MAX3996 toc09
MAX3996
STARTUP WITH SLOW
RAMPING SUPPLY
MAX3996 toc10
TRANSMITTER ENABLE
V
CC
3.3V
3.3V
MAX3996 toc11
3.3V
0V
V
CC
FAULT
TX_DISABLE
LOW
LOW
t_init = 23mS
V
CC
FAULT
TX_DISABLE
0V
LOW
LOW
FAULT
TX_DISABLE
LOW
HIGH
t_on = 37µs
LOW
LASER
OUPUT
LASER
OUPUT
LASER
OUPUT
10.0ms/div
10.0ms/div
20.0µs/div
TRANSMITTER DISABLE
MAX3996 toc12
RESPONSE TO FAULT
MAX3996 toc13
FAULT RECOVERY TIME
EXTERNAL
FAULT REMOVED
V
TC
FAULT
OFF
MAX3996 toc14
V
CC
3.3V
t_off = 60ns
V
MON2
EXTERNALLY
FORCED FAULT
ON
t_fault = 14µs
FAULT
LOW
HIGH
LOW
I
BIAS
HIGH
FAULT
ELECTRICAL
OUPUT
20.0ns/div
10.0µs/div
TX_DISABLE
LOW
LASER
OUPUT
10.0µs/div
TX_DISABLE
LASER
OUPUT
FREQUENT ASSERTION OF
TX_DISABLE
EXTERNALLY
FORCED FAULT
OV
MAX3996 toc15
V
TC
FAULT
TX_DISABLE
LASER
OUPUT
1.00ms/div
_______________________________________________________________________________________
5
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