MAX3740AETG+T Maxim Integrated Products, MAX3740AETG+T Datasheet - Page 13

• 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

Figures 4 and 5 show simplified input and output circuits
for the MAX3740A laser driver. Figure 6 shows the fault
circuit interface.
To minimize inductance, keep the connections between
the MAX3740A output pins and laser diode as short as
possible. Use good high-frequency layout techniques
and multilayer boards with uninterrupted ground planes
to minimize EMI and crosstalk.
Laser package inductance causes the laser impedance
to increase at high frequencies, leading to ringing, over-
shoot, and degradation of the laser output. A laser com-
pensation filter network can be used to reduce the laser
impedance at high frequencies, thereby reducing output
ringing and overshoot.
Figure 5. Simplified Output Structure
Figure 6. Fault Circuit Interface
R
OUT-
MAX3740A
3.2Gbps SFP VCSEL Driver with Diagnostic
Designing the Compensation Filter
R
OUT+
Applications Information
______________________________________________________________________________________
V
CC
Layout Considerations
V
CC
Interface Models
PACKAGE
MAX3740A
0.5pF
0.5pF
FAULT
1nH
1nH
Network
OUT+
OUT-
The compensation components (R
easily determined by experimentation. Begin with R
50Ω and C
mitter response is obtained (Figure 7). Refer to
Application Note HFAN-2-0: Interfacing Maxim Laser
Drives with Laser Diodes for more information.
The exposed pad on the 24-pin thin QFN provides a very
low thermal resistance path for heat removal from the IC.
The pad is also electrical ground on the MAX3740A and
must be soldered to the circuit board ground for proper
thermal and electrical performance. Refer to Maxim
Application Note HFAN-08.1: Thermal Considerations for
QFN and Other Exposed-Pad Packages for additional
information.
The International Electrotechnical Commission (IEC)
determines standards for hazardous light emissions from
fiber optic transmitters. IEC 825 defines the maximum
light output for various hazard levels. The MAX3740A
provides features that facilitate compliance with IEC 825.
A common safety precaution is single-point fault toler-
ance, whereby one unplanned short, open, or resistive
connection does not cause excess light output. Using
this laser driver alone does not ensure that a transmitter
design is compliant with IEC 825. The entire transmitter
circuit and component selections must be considered.
Customers must determine the level of fault tolerance
required by their applications, recognizing that Maxim
products are not designed or authorized for use as com-
ponents in systems intended for surgical implant into the
body, for applications intended to support or sustain life,
or for any other application where the failure of a Maxim
product could create a situation where personal injury or
death may occur.
Figure 7. Laser Compensation
F
= 1pF. Increase C
Exposed-Pad (EP) Package
CORRECTLY COMPENSATED
Laser Safety and IEC 825
UNCOMPENSATED
OVERCOMPENSATED
TIME
F
until the desired trans-
Monitors
F
and C
F
) are most
F
13
=