1Gbps to 11.3Gbps, SFP+ Laser Driver with Laser Impedance Mismatch Tolerance

11.3Gbps Laser Driver Consumes Only 225mW, Ideal for Building < 1W SFP+ Optical Modules

Please check latest availability status for a specific part variant.


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 transmitter optical subassembly (TOSA) with a 25Ω flex circuit. The unique design of the output stage enables use of unmatched TOSAs, greatly reducing headroom limitations and lowering power consumption.

The device receives differential CML-compatible signals with on-chip line termination. It can deliver laser modulation current of up to 80mA, at an edge speed of 22ps (20% to 80%), into a 5Ω to 25Ω 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 disabled from a single pin.

A 3-wire digital interface reduces the pin count and permits adjustment of input equalization, pulse-width adjustment, Tx polarity, Tx deemphasis, modulation current, and bias current without the need for external components. The MAX3946 is available in a 4mm x 4mm, 24-pin TQFN package.
MAX3946: Functional Diagram MAX3946: Functional Diagram Enlarge+

Key Features

  • 225mW Power Dissipation Enables < 1W SFP+ Modules
  • Up to 100mW Power Consumption Reduction by Enabling the Use of Unmatched FP/DFB TOSAs
  • Supports SFF-8431 SFP+ MSA and SFF-8472 Digital Diagnostic
  • 225mW Power Dissipation at 3.3V (IMOD = 40mA, IBIAS = 60mA Assuming 25Ω TOSA)
  • Single +3.3V Power Supply
  • Up to 11.3Gbps (NRZ) Operation
  • Programmable Modulation Current from 10mA to 100mA (5Ω Load)
  • Programmable Bias Current from 5mA to 80mA
  • Programmable Input Equalization
  • Programmable Output Deemphasis
  • 25Ω Output Back Termination at TOUT+ and TOUT-
  • DJ Performance 7psP-P with Mismatched Differential Load (5Ω)
  • DJ Performance 5psP-P with Mismatched Differential Load (25Ω)
  • DJ Performance 5psP-P with 50Ω Differential Load
  • Programmable Pulse Width
  • Edge Transition Times of 22ps
  • Bias Current Monitor
  • Integrated Eye Safety Features
  • 3-Wire Digital Interface
  • -40°C to +95°C Operation


  • 10GBASE-LR SFP+ Optical Transceivers
  • 10GBASE-LRM SFP+ Optical Transceivers
  • 10GFC SFP+ Optical Transceivers
  • 4x/8x FC SFP+ Optical Transceivers
  • OC192-SR XFP/SFP+ SDH/SONET Transceivers

See parametric specs for Laser Drivers (21)

Part NumberTarget Oper. Range
Data Rate
Data Rate
minmaxtypmaxmaxSee Notes
MAX3946 5 to >101062113003.368CML10080
$4.20 @1k

Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX3946EVKIT: Evaluation Kit for the MAX3946
Product Reliability Reports: MAX3946.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

Quality Management System >
Environmental Management System >


Related Resources