MAX3740AETG+T Maxim Integrated Products, MAX3740AETG+T Datasheet - Page 10

• Manufacturer Part Number: MAX3740AETG+T
• Description: IC DRIVER SFP VCSEL 24-TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driverr

Specifications of MAX3740AETG+T

• Data Rate: 3.2Gbps
• Number Of Channels: 1
• Voltage - Supply: 2.97 V ~ 3.63 V
• Current - Supply: 55mA
• Current - Modulation: 15mA
• Current - Bias: 15mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 24-TQFN Exposed Pad
• Mounting Type: Surface Mount
• Supply Voltage (max): 6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Supply Current: 55 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

3.2Gbps SFP VCSEL Driver with Diagnostic
Monitors
The modulation circuitry consists of an input buffer, a
current mirror, and a high-speed current switch (Figure
3). The modulator drives up to 15mA of modulation into
a 50Ω VCSEL load.
The amplitude of the modulation current is set with
resistors at MODSET and temperature coefficient (TC1,
TC2) pins. The resistor at MODSET (R
grams the temperature-stable portion of the modulation
current, and the resistor between TC1 and TC2 (R
programs the temperature coefficient of the modulation
current. For appropriate R
the Typical Operating Characteristics section.
Table 2. Circuit Response to Various Single-Point Faults (Closed-Loop APC Configuration)
* A fault state asserts the FAULT pin, disables the modulator output, and disables the bias output.
10
TX_DISABLE
PIN NAME
SQUELCH
BIASMON
PWRMON
PEAKSET
MODSET
BIASSET
______________________________________________________________________________________
FAULT
COMP
OUT+
OUT-
BIAS
TC1
TC2
REF
IN+
MD
IN-
Does not affect laser power.
Modulation and bias current are disabled.
Does not affect laser power.
Does not affect laser power.
Does not affect laser power.
Does not affect laser power.
The laser modulation is increased, but average power
is not affected.
Modulation current is disabled.
Does not affect laser power.
Modulation current is disabled.
Does not affect laser power.
Laser bias is disabled.
Fault state* occurs. Note that VCSEL emissions may
continue; care must be taken to prevent this condition.
Fault state* occurs.
The bias current is reduced, and the average power of
the laser output is reduced.
I
the bias-monitor fault threshold is exceeded, a fault is
signaled.
I
the bias-monitor fault threshold is exceeded, a fault is
signaled.
Fault state* occurs.
BIAS
BIAS
increases to the value determined by R
increases to the value determined by R
CIRCUIT RESPONSE TO V
TC
and R
Modulation Circuit
MODSET
MODSET
values, see
CC
) pro-
SHORT
TC
)
BIASSET
BIASSET
Select a communications-grade laser with a rise time of
260ps or better for 1.25Gbps, or 130ps or better for
2.5Gbps applications. Use a high-efficiency laser that
requires low modulation current and generates a low-
voltage swing. Trim the leads to reduce laser package
inductance. The typical package leads have induc-
tance of 25nH per inch (1nH/mm). This inductance
causes a large voltage swing across the laser. A com-
pensation filter network can also be used to reduce
ringing, edge speed, and voltage swing (see the
Designing the Compensation Filter Network section).
; if
; if
Does not affect laser power.
Normal condition for circuit operation.
Does not affect laser power.
Does not affect laser power.
Does not affect laser power.
Does not affect laser power.
Modulation current is disabled.
The laser modulation is increased, but average power
is not affected.
Does not affect laser power.
Modulation current is disabled.
Does not affect laser power.
Fault state* occurs.
Disables VCSEL.
Does not affect laser power.
I
the bias monitor fault threshold is exceeded, a fault is
signaled.
The bias current is reduced, and the average power of
the laser output is reduced.
The bias current is reduced, and the average power of
the laser output is reduced.
Does not affect laser power.
BIAS
increases to the value determined by R
CIRCUIT RESPONSE TO GND SHORT
Design Procedure
Select Laser
BIASSET
; if