Question
I would like to know if my laser diode is of type B and I want to use it in constant current mode. The anode of the LD is internally connected to the case. Now I would like the case to be grounded, how should I connect it with the WLD3343 LD Driver? Ground the anode and then connect the cathode to pin 11? Can pin 11 supply a negative voltage so that the LD can be lit up?
Answer
If the PD is isolated from the LD then it is a B type laser. If your supply output ground can float in reference to earth ground you can make standard connections as shown for CC mode in the WLD3343 Datasheet/Manual or WLD33ND & WLD33ND-EV Evaluation Board Datasheet. If the supply can not be isolated from earth ground then you must use a negative power supply and connect it as shown in the attached diagram. If you use a negative supply you must use a negative voltage for pin 2 (current input setting) or you can add the op amp as shown to invert the signal for use with a D/A.
Laser Class Schematic