The ADN2830 provides closed loop control of the average optical power of a continuous wave (CW) laser diode (LD) after initial factory setup. The control loop adjusts the laser Ibias to maintain a constant Back-Facet Monitor Photo Diode (MPD) current and hence a constant laser optical
power. The external PSET resistor is adjusted during factory setup to set the desired optical power. RPSET is set at 1.23/IAV, where IAVis the MPD current corresponding to the desired optical power. Programmable alarms are provided for laser fail (end of life), and laser degrade (impending fail).
To provide monitoring of the MPD current, the MPD can be connected to the IMPD pin. In this case the MPD current is mirrored to the IMPDMON pin to provide a monitor, and internally to the PSET pin to close the control loop. By closing the feedback using IBMON rather than an MPD
connected to PSET , the device is configured to control a constant current in the laser rather than a constant optical output power.