The MAX3738 is a +3.3V laser driver designed for multi-rate transceiver modules with data rates from 155Mbps to 2.7Gbps. Lasers can be DC-coupled to the MAX3738 for reduced component count and ease of multirate operation. Laser extinction ratio control (ERC) combines the features of automatic power control (APC), modulation compensation, and built-in thermal compensation. The APC loop maintains constant average optical power. Modulation compensation increases the modulation current in proportion to the bias current. These control loops, combined with thermal compensation, maintain a constant optical extinction ratio over temperature and lifetime. The MAX3738 accepts differential data input signals. The wide 5mA to 60mA (up to 85mA AC-coupled) modulation current range and up to 100mA bias current range, make the MAX3738 ideal for driving FP/DFB lasers in fiber optic modules. External resistors set the required laser current levels. The MAX3738 provides transmit disable control (TX_DISABLE), single-point fault tolerance, bias-current monitoring, and photocurrent monitoring. The device also offers a latched failure output (TX_FAULT) to indicate faults, such as when the APC loop is no longer able to maintain the average optical power at the required level. The MAX3738 is compliant with the SFF-8472 transmitter diagnostic and SFP MSA timing requirements. The MAX3738 is offered in a 4mm x 4mm, 24-pin thin QFN package and operates over the extended -40°C to 85°C ambient temperature range, and at a supply voltage of 3.3V.
The MAX3738 is a +3.3 V laser driver designed for multirate SFF/SFP transceiver modules covering data rates from 155 Mbps to 2.7 Gbps. It provides automatic power control, modulation compensation, and extinction‑ratio control, and complies with SFF‑8472 and SFP MSA timing requirements. Typical applications include multirate OC‑3 to OC‑48 transceivers, Gigabit Ethernet, and Fibre Channel modules.
Key features include a wide modulation current range (5 mA‑85 mA), bias‑current range up to 100 mA, TX_DISABLE and TX_FAULT pins for safety, and an exposed‑pad thin‑QFN package. The datasheet supplies absolute maximum ratings, electrical characteristics, pin descriptions, typical operating curves, layout recommendations, and package information.
| Bias Current Range | 1 mA to 100 mA |
|---|---|
| Operating Temperature Range | -40 °C to +85 °C |
| Package | 24‑pin thin QFN, 4 mm × 4 mm |
| Transistor Count | 1884 |
TX_DISABLE is a transmitter‑disable input; the laser output is disabled when the pin is asserted high.
It is offered in a 24‑pin thin QFN package measuring 4 mm × 4 mm.
External resistors set the bias current, which can be programmed from 1 mA up to 100 mA.