19-5182; Rev 0; 3/10
1.0625Gbps to 11.3Gbps, SFP+ Laser Driver
with Laser Impedance Mismatch Tolerance
The MAX3946 is a +3.3V, multirate, low-power laser
diode driver designed for Ethernet and Fibre Channel
transmission systems at data rates up to 11.3Gbps.
This device is optimized to drive a differential transmit-
ter optical subassembly (TOSA) with a 25I flex circuit.
The unique design of the output stage enables use of
unmatched TOSAs, greatly reducing headroom limita-
tions and lowering power consumption.
The device receives differential CML-compatible signals
with on-chip line termination. It can deliver laser modula-
tion current of up to 80mA, at an edge speed of 20ps
(20% to 80%), into a 5I to 25I external differential load.
The device is designed to have a symmetrical output
stage with on-chip back terminations integrated into
its outputs. A high-bandwidth, fully differential signal
path is implemented to minimize deterministic jitter. An
equalization block can be activated to compensate for
the SFP+ connector. The integrated bias circuit provides
programmable laser bias current up to 80mA. Both the
laser bias generator and the laser modulator can be dis-
abled from a single pin, DISABLE.
A 3-wire digital interface reduces the pin count and
permits adjustment of input equalization, pulse-width
adjustment, Tx polarity, Tx deemphasis, modulation cur-
rent, and bias current without the need for external com-
ponents. The MAX3946 is available in a 4mm x 4mm,
24-pin TQFN package.
4x/8x FC SFP+ Optical Transceivers
10GFC SFP+ Optical Transceivers
10GBASE-LR SFP+ Optical Transceivers
10GBASE-LRM SFP+ Optical Transceivers
OC192-SR XFP/SFP+ Transceivers
S 225mW Power Dissipation Enables < 1W SFP+
S Up to 100mW Power Consumption Reduction by
Enabling the Use of Unmatched FP/DFB TOSAs
S Supports SFF-8431 SFP+ MSA and SFF-8472
S 225mW Power Dissipation at 3.3V (IMOD = 40mA,
IBIAS = 60mA Assuming 25I TOSA)
S Single +3.3V Power Supply
S Up to 11.3Gbps (NRZ) Operation
S Programmable Modulation Current from 10mA to
100mA (5I Load)
S Programmable Bias Current from 5mA to 80mA
S Programmable Input Equalization
S Programmable Output Deemphasis
S 25I Output Back Termination at TOUT+ and
S DJ Performance 7psP-P with Mismatched
Differential Load (5I)
S DJ Performance 5psP-P with Mismatched
Differential Load (25I)
S DJ Performance 5psP-P with 50I Differential Load
S Programmable Pulse Width
S Edge Transition Times of 20ps
S Bias Current Monitor
S Integrated Eye Safety Features
S 3-Wire Digital Interface
S -40°C to +95°C Operation
-40°C to +85°C
Note: Parts are guaranteed by design and characterization to
operate over the -40°C to +95°C ambient temperature range
(TA) and are tested up to +85°C.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.