The MAX3869 is a complete, single +3.3V laser driver for SDH/SONET applications up to 2.5Gbps. The device accepts differential PECL data and clock inputs and provides bias and modulation currents for driving a laser. A synchronizing input latch can be used (if a clock signal is available) to reduce jitter. An automatic power control (APC) feedback loop is incorporated to maintain a constant average optical power over temperature and lifetime. The wide modulation current range of 5mA to 60mA and bias current of 1mA to 100mA are easy to program, making this product ideal for use in various SDH/SONET applications. The MAX3869 also provides enable control, two current monitors that are directly proportional to the laser bias and modulation currents, and a failure-monitor output to indicate when the APC loop is unable to maintain the average optical power. The MAX3869 is available in 32-pin TQFP and small 32-pin QFN packages as well as dice.
The Maxim MAX3869 provides bias and modulation current sources for high‑speed optical transmitters. It accepts differential PECL data and clock inputs, includes an automatic power control (APC) loop, and offers enable control, current monitors, and a failure‑monitor output. The device is available in 32‑pin TQFP and QFN packages and is designed for 25 Ω laser loads.
Key features include programmable bias (1 mA‑100 mA) and modulation (5 mA‑60 mA) currents, 87 ps rise/fall times, and a built‑in APC loop that maintains constant average optical power over temperature and lifetime. External components such as a damping resistor, pull‑up inductor, and AC‑coupling capacitor are recommended for optimal performance.
| Supply Voltage | +3.3 V (single‑supply) |
|---|---|
| Bias Current Range | 1 mA to 100 mA (programmable) |
| Modulation Current Range | 5 mA to 60 mA (programmable) |
| Rise/Fall Time | 87 ps |
| Supply Current at +3.3 V | 64 mA |
| Maximum Data Rate | 2.5 Gbps |
| APC Failure Indicator | FAIL pin goes low on APC loop failure |
Both the bias and modulation currents are turned off when ENABLE is low.
The FAIL TTL/CMOS output pin is driven low when the APC loop cannot maintain the desired average optical power.
A 0.1 µF capacitor is recommended for the APCFILT pin to filter APC loop noise.