11.3Gbps, Low-Power, DC-Coupled Laser Driver

168mW 40GBASE-LR4 Laser Driver Beats QSFP+ Spec

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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 25Ω 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 modulation currents of up to 85mA at an edge speed of 26ps (20% to 80%) into a 5Ω external differential load. The device is designed to have a high-bandwidth differential 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, polarity, output deemphasis, and modulation and DC currents without the need for external components. The MAX3948 is available in a 3mm × 3mm, 16-pin TQFN package, and is specified for the -40°C to +95°C extended temperature range.

Key Features

  • Lowest Power Consumption
    • 168mW Typical IC Power Dissipation at 3.3V (LDMOD = 40mA, LDDC = 20mA)
    • 383mW Total Transmitter Power Dissipation at 3.3V Including LDMOD = 40mA, LDDC = 20mA
    • Enables < 1W Maximum Total SFP+ Module Power Dissipation
    • Enables < 2.5W Maximum Total QSFP+ Module Power Dissipation
  • Saves Board Space
    • Small 3mm × 3mm Package
    • DC-Coupling to the Laser Reduces External Component Count
  • 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
  • Safety
    • Supports SFF-8431 SFP+ MSA and SFF-8472 Digital Diagnostic
    • Integrated Eye Safety Features with Maskable Faults
    • DC Current Monitor


  • 10GBASE-LR SFP+ Optical Transceivers
  • 10GBASE-LRM SFP+ Optical Transceivers
  • 40GBASE-LR4 QSFP+ Optical Transceivers
  • OC192-SR SFP+ SDH/SONET Transceivers

See parametric specs for Laser Drivers (21)

Part NumberTarget Oper. Range
Data Rate
Data Rate
minmaxtypmaxmaxSee Notes
MAX3948 5 to >101000113003.35185100
$6.17 @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.

MAX3948EVKIT: Evaluation Kit for the MAX3948

Tools & Models

  • MAX3948 IBIS Model
  • Product Reliability Reports: MAX3948.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.

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