The MAX3949 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 use of unmatched TOSAs.The device receives differential AC-coupled signals with on-chip termination. It can deliver laser modulation currents of up to 85mA at an edge speed of 22ps (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+ host connector losses. The integrated bias circuit provides programmable laser bias currents up to 105mA. Both the laser bias current generator and the laser modulator can be disabled from a single pin.The use of a 3-wire digital interface reduces the pin count while permitting adjustment of input equalization, polarity, output deemphasis, and modulation and bias currents without the need for external components. The device is available in a 3mm x 3mm, 16-pin TQFN package, and is specified for the -40°C to +95°C extended temperature range.Applications10GBASE-LR SFP+ Optical Transceivers10GBASE-LRM SFP+ Optical TransceiversOC192-SR SFP+ SDH/SONET Transceivers