MAX3735AETG+ Maxim Integrated Products, MAX3735AETG+ Datasheet - Page 10

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

Specifications of MAX3735AETG+

• 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
• Operating Supply Voltage: 3.3 V
• Supply Current: 27 mA
• Maximum Operating Temperature: + 85 C
• Maximum Power Dissipation: 1354 mW
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

2.7Gbps, Low-Power SFP Laser Drivers
Figure 4. Functional Diagram
To maintain constant average optical power, the
MAX3735/MAX3735A incorporate an APC loop to com-
pensate for the changes in laser threshold current over
temperature and lifetime. A back-facet photodiode
mounted in the laser package is used to convert the
optical power into a photocurrent. The APC loop
adjusts the laser bias current so that the monitor cur-
rent is matched to a reference current set by R
The time constant of the APC loop is determined by an
external capacitor (C
see the Applications Information section.
The safety circuitry contains an input disable
(TX_DISABLE), a latched fault output (TX_FAULT), and
fault detectors (Figure 5). This circuitry monitors the
operation of the laser driver and forces a shutdown if a
fault is detected (Table 1). A single-point fault can be a
short to V
10
______________________________________________________________________________________
R
R
PC_MON
BC_MON
CC
PC_MON
BC_MON
or GND. See Table 2 to view the circuit
IN+
IN-
100Ω
V
V
APC
CC
CC
MODSET
R
MODSET
). For possible C
I
I
Laser-Biasing and APC
BIAS
INPUT BUFFER
76
MD
1
V
BG
X270
Safety Circuitry
TX_FAULT
ENABLE
I
MOD
SAFETY LOGIC
APC
DETECTOR
POWER
TX_DISABLE
AND
APCSET
values,
MAX3735A
TO 10kΩ)
MAX3735
DATA
PATH
(4.7kΩ
I
ENABLE
BIAS
V
CC
V
.
SHUTDOWN
CC
response to various single-point failures. The transmit
fault condition is latched until reset by a toggle of
TX_DISABLE or V
laser diode shutdown through the optional shutdown
circuitry (see the Typical Applications Circuit). The
TX_FAULT pin should be pulled high with a 4.7kΩ to
10kΩ resistor to V
The MAX3735/MAX3735A feature monitors (BC_MON,
PC_MON) for bias current (I
(I
of the currents and developing voltages across external
resistors connected to ground. Voltages greater than
1.38V at PC_MON or BC_MON result in a fault state.
For example, connecting a 100Ω resistor to ground on
each monitor output gives the following relationships:
MD
x38
). The monitors are realized by mirroring a fraction
APCFILT1
C
APC
V
V
BC_MON
PC_MON
APCFILT2
V
CC
CC
CC
Safety Circuitry Current Monitors
. The laser driver offers redundant
I
x1
V
as required by the SFP MSA.
APCSET
BG
= I
= (I
I
MOD
MD
SHUTDOWN
BIAS
OUT-
OUT+
BIAS
APCSET
MD
x 100Ω
15Ω
BIAS
/ 76) x 100Ω
V
R
CC
R
APCSET
D
) and photo current
I
I
BIAS
MD
V
C
CC
MD