MAX3735AETG+T Maxim Integrated Products, MAX3735AETG+T Datasheet - Page 11

• Manufacturer Part Number: MAX3735AETG+T
• Description: IC LSR DRVR 2.7GBPS 3.63V 24TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3735AETG+T

• Data Rate: 2.7Gbps
• Number Of Channels: 1
• Voltage - Supply: 2.97 V ~ 3.63 V
• Current - Supply: 27mA
• Current - Modulation: 85mA
• Current - Bias: 100mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 24-TQFN Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

When designing a laser transmitter, the optical output
usually is expressed in terms of average power and
extinction ratio. Table 3 shows relationships helpful in
converting between the optical average power and the
modulation current. These relationships are valid if the
mark density and duty cycle of the optical waveform
are 50%.
For a given laser power (P
extinction ratio (r
lated using Table 3. See the Modulation Current vs.
R
Table 1. Typical Fault Conditions
Figure 5. Safety Circuitry
MODSET
1.
2.
3.
4.
If any of the I/O pins is shorted to GND or V
point failure, see Table 2), and the bias current or the
photocurrent exceed the programmed threshold.
End-of-life (EOL) condition of the laser diode. The bias
current and/or the photocurrent exceed the
programmed threshold.
Laser cathode is grounded and the photocurrent
exceeds the programmed thresholds.
N o feed b ack for the AP C l oop ( b r oken i nter connecti on,
d efecti ve m oni tor p hotod i od e) , and the b i as cur r ent
exceed s the p r og r am m ed thr eshol d .
Programming the Modulation Current
graph in the Typical Operating Characteristics
e
), the modulation current can be calcu-
______________________________________________________________________________________
R
R
PC_MON
BC_MON
2.7Gbps, Low-Power SFP Laser Drivers
TX_DISABLE
PC_MON
BC_MON
AVG
Design Procedure
V
CC
), slope efficiency (η), and
POR AND COUNTER
COUNTER FOR
V
V
CC
CC
FOR t_init
t_onfault
I
I
BIAS
MD
76
1
DETECTOR
MODSET
CIRCUIT
SHORT-
CC
V
V
BG
BG
(single-
COMP
COMP
section, and select the value of R
sponds to the required current at +25°C.
Program the average optical power by adjusting -R
SET
tor current to be maintained over temperature and
lifetime. See the Monitor Diode Current vs. R
graph in the Typical Operating Characteristics section,
and select the value of R
required current.
To minimize optical output aberrations caused by sig-
nal reflections at the electrical interface to the laser
diode, a series-damping resistor (R
(Figure 4). Additionally, the MAX3735/MAX3735A out-
puts are optimized for a 15Ω load. Therefore, the series
combination of R
laser-diode resistance, should equal 15Ω. Typical val-
ues for R
a bypass capacitor (0.01µF typ) as close as possible to
the anode of the laser diode. An RC shunt network
between the laser cathode and ground minimizes opti-
cal output aberrations. Starting values for most coaxial
lasers are R
Adjust these values experimentally until the optical out-
put waveform is optimized. Refer to Maxim Application
Note: HFAN 02.0: Interfacing Maxim’s Laser Drivers to
Laser Diodes for more information.
. To select the resistance, determine the desired moni-
R
S
LATCH
RS
D
100ns DELAY
Q
are 8Ω to 13Ω. For best performance, place
MAX3735A
MAX3735
COMP
OPEN COLLECTOR
Interfacing with Laser Diodes
D
= 50Ω in series with C
Programming the APC Loop
and R
I
ENABLE
I
ENABLE
MOD
BIAS
CMOS
TTL
APCSET
L
, where R
SHUTDOWN
TX_FAULT
that corresponds to the
MODSET
L
D
represents the
) is required
COMP
that corre-
APCSET
= 8pF.
APC-
11