MAX3737ETJ+T Maxim Integrated Products, MAX3737ETJ+T Datasheet - Page 8

• Manufacturer Part Number: MAX3737ETJ+T
• Description: IC LSR DRVR 2.7GBPS 3.63V 32TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3737ETJ+T

• Data Rate: 2.7Gbps
• Number Of Channels: 1
• Voltage - Supply: 2.97 V ~ 3.63 V
• Current - Supply: 47mA
• Current - Modulation: 85mA
• Current - Bias: 100mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 32-WFQFN Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX3737 laser driver consists of three main parts: a
high-speed modulation driver, biasing block with ERC,
and safety circuitry. The circuit design is optimized for
high-speed, low-voltage (+3.3V) operation (Figure 4).
The output stage is composed of a high-speed differ-
ential pair and a programmable modulation current
source. The MAX3737 is optimized for driving a 15Ω
load. The minimum instantaneous voltage required at
OUT+ is 0.7V for modulation current up to 60mA and
0.75V for currents from 60mA to 85mA. Operation
above 60mA can be accomplished by AC-coupling or
with sufficient voltage at the laser to meet the driver
output voltage requirement.
To interface with the laser diode, a damping resistor (R
is required. The combined resistance due to the series
damping resistor and the equivalent series resistance
(ESR) of the laser diode should equal 15Ω. To further
damp aberrations caused by laser diode parasitic induc-
tance, an RC shunt network may be necessary. Refer to
Maxim Application Note HFAN 02.0: Interfacing Maxim’s
Laser Drivers to Laser Diodes for more information.
Multirate Laser Driver with Extinction
Ratio Control
Figure 1. Required Input Signal and Output Polarity
Figure 3. Supply Filter
8
(V
IN
+) - (V
CURRENT
VOLTAGE
_______________________________________________________________________________________
I
OUT
V
V
IN
IN
IN
-)
+
+
-
High-Speed Modulation Driver
SINGLE ENDED
DIFFERENTIAL
Detailed Description
TIME
VOLTAGE
SUPPLY
SOURCE
NOISE
C1
0.1µF
100mV (MIN)
1200mV (MAX)
200mV
2400mV (MAX)
I
MOD
FILTER DEFINED BY SFP MSA
P-P
(MIN),
HOST BOARD
C2
10µF
D
)
1µH
L1
At data rates of 2.7Gbps, any capacitive load at the
cathode of a laser diode degrades optical output perfor-
mance. Because the BIAS output is directly connected
to the laser cathode, minimize the parasitic capacitance
associated with the pin by using an inductor to isolate
the BIAS pin parasitics from the laser cathode.
The extinction ratio (r
divided by the off-state power. Extinction ratio remains
constant if peak-to-peak and average power are held
constant:
Average power is regulated using APC, which keeps
constant current from a photodiode coupled to the
laser. Peak-to-peak power is maintained by compen-
sating the modulation current for reduced slope effi-
ciency (η) of the laser over time and temperature:
Figure 2. Test Circuit for Characterization
C3
0.1µF
MAX3737
OUT+
OUT+
OUT-
OUT-
r
e =
OPTIONAL
V
CC
(2P
OPTIONAL
I
30Ω
OUT
0.5pF
MODULE
AVG
+
V
P
P
CC
P-P
AVG
+ P
30Ω
DRIVER V
TO LASER
e
Extinction Ratio Control
) is the laser on-state power
= η x I
Z
Z
P-P
0
0
=
= 30Ω
= 30Ω
CC
ρ
) / (2P
I
MON
MD
MOD
AVG
30Ω
75Ω
Z
0
- P
= 50Ω
P-P
OSCILLOSCOPE
)
50Ω