Optical-module driver for 10G+ SFP+ links
The MAX3949ETE+T is a single-channel laser diode driver from Analog Devices, designed to drive a laser diode at data rates up to 11.3 Gbps — the rate used in 10G SFP+ and 10GBASE-LR/ER optical transceivers, plus the 8.5 Gbps Fibre Channel standard. It is a direct-fit IC for the transmitter side of a small-form-factor pluggable module where the PCB real estate is tight and the supply rail is 3.3 V nominal.
The driver sources a programmable bias current up to 105 mA and a modulation current up to 85 mA. The bias sets the laser's DC operating point above threshold; the modulation current is the AC swing that produces the optical extinction ratio. For a typical 1310 nm FP or DFB laser with a threshold around 10–20 mA, the 105 mA bias ceiling leaves headroom for temperature drift and aging without saturating the laser's power curve. Supply current is 55 mA typical — the driver's own consumption is separate from the bias and modulation currents delivered to the laser, so the total current draw from the 2.95–3.63 V rail is the sum of the three. The 55 mA figure means the driver itself does not dominate the module power budget; the laser's bias and modulation do.
Package footprint and thermal land
Housed in a 16-lead WFQFN with an exposed pad, 3x3 mm body (the supplier device package is called 16-TQFN). The 0.5 mm pitch QFN footprint is standard for SFP+ transmit-side ICs and routes out cleanly on a 4-layer board.