The MAX3663 is a complete, +3.3V laser driver with automatic power-control (APC) circuitry for SDH/SONET applications up to 622Mbps. It accepts differential PECL inputs, provides bias and modulation currents, and operates over a -40C to +85C temperature range. An APC feedback loop is incorporated to maintain a constant average optical power over temperature and lifetime. The wide modulation current range from 5mA to 75mA and bias current of 1mA to 80mA are easy to program, making this product ideal for use in various SDH/SONET applications. Two pins are provided to monitor the current levels in the laser: BIASMON with current proportional to laser bias current, and MODMON with current proportional to laser modulation. The MAX3663 also provides enable control and a failuremonitor output to indicate when the APC loop is unable to maintain the average optical power. The MAX3663 is available in a compact 4mm x 4mm 24-pin thin QFN package.