MAXIM MAX3946ETG+T

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 25Q 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 5Q to 25Q 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 × 4mm 24-pin TQFN package.

• 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 (lMOD = 40mA, IBIAS = 60mA Assuming 25Q TOSA)
• Single +3.3V Power Supply
• Up to 11.3Gbps (NRZ) Operation
• Programmable Modulation Current from 10mA to 100mA (5Q Load)
• Programmable Bias Current from 5mA to 80mA
• Programmable Input Equalization
• Programmable Output Deemphasis
• 25Q 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 50Q 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

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