MAX3946：1Gbps 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

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.

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