MAX3948 Datasheet, PDF (1/37 Pages) Maxim Integrated Products – 11.3Gbps, Low-Power, DC-Coupled Laser Driver

19-5943; Rev 0; 6/11
EVALUATION KIT AVAILABLE
MAX3948
11.3Gbps, Low-Power, DC-Coupled Laser Driver
General Description
The MAX3948 is a 3.3V, multirate, low-power laser diode
driver designed for Ethernet, Fibre Channel, and SONET
transmission systems at data rates up to 11.3Gbps. This
device is optimized to drive a differential transmitter
optical subassembly (TOSA) with a 25I flex circuit. The
unique design of the output stage enables DC-coupling
to unmatched TOSAs, thereby lowering transmitter power
consumption by more than 100mW.
The MAX3948 receives differential AC-coupled signals
with on-chip termination. It can deliver laser modula-
tion currents of up to 85mA at an edge speed of 26ps
(20% to 80%) into a 5I external differential load. The
device is designed to have a high-bandwidth differen-
tial signal path with on-chip back termination resistors
integrated into its outputs. An input equalization block
can be activated to compensate for SFP+/QSFP+ host
connector losses. The integrated DC circuit provides
programmable laser DC currents up to 61mA. Both the
laser DC current generator and the laser modulator can
be disabled from a single pin.
The device offers one dedicated pin (VSEL) to program up
to four channel addresses for multichannel applications.
The use of a 3-wire digital interface reduces the pin count
while permitting adjustment of input equalization, polar-
ity, output deemphasis, and modulation and DC currents
without the need for external components. The MAX3948
is available in a 3mm x 3mm, 16-pin TQFN package, and
is specified for the -40NC to +95NC extended temperature
range.
Applications
40GBASE-LR4 QSFP+ Optical Transceivers
10GBASE-LR SFP+ Optical Transceivers
10GBASE-LRM SFP+ Optical Transceivers
OC192-SR SFP+ SDH/SONET Transceivers
Benefits and Features
S Lowest Power Consumption
 168mW Typical IC Power Dissipation at 3.3V
(LD_MOD = 40mA, LD_DC = 20mA)
 383mW Total Transmitter Power Dissipation at
3.3V Including LD_MOD = 40mA, LD_DC = 20mA
 Enables < 1W Maximum Total SFP+ Module
Power Dissipation
 Enables < 2.5W Maximum Total QSFP+ Module
Power Dissipation
S Saves Board Space
 Small 3mm x 3mm Package
 DC-Coupling to the Laser Reduces External
Component Count
S Flexibility
 Operate Up to Four MAX3948 ICs Over Single
3-Wire Digital Interface
 Programmable Modulation Current Up to
85mA (5ω Load)
 Programmable DC Current Up to 61mA
(Translates to Up to 100mA Laser Bias Current)
 Programmable Input Equalization and Output
Deemphasis
S Safety
 Supports SFF-8431 SFP+ MSA and SFF-8472
Digital Diagnostic
 Integrated Eye Safety Features with Maskable
Faults
 DC Current Monitor
Ordering Information appears at end of data sheet.
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