IP500 Laser Diode Controller
Chapter 2: Setup and Operation
Page 4
3037-D02
2.2. Operation
2.2.1. Automatic Constant Current Control (ACC)
1.
Set JMP1 to either “AG” for laser diodes with grounded anodes or “CG”
for laser diodes with grounded cathodes. JMP1 is located on the left side
of the unit. Always disable the laser driver prior to changing modes.
2. Set JMP2 t
o “ACC” for constant current operation. JMP2 is located on the
left side of the unit. Always disable the laser driver prior to changing
modes.
3. Apply power to the unit.
4. Using a digital multimeter measure the ILIM Test point with respect to the
TP GND Test point (all measurements will be with respect to TP GND).
Adjust the ILIM ADJ potentiometer for the maximum current that the laser
must be limited to. The transfer function is 1 V = 1 A, with a maximum
adjustment of approximately 0.500 V or 500 mA.
5. If a monitor photodiode (MPD) is connected, measure the PLIM Test point
and adjust the PLIM ADJ pot for the maximum MPD current expected.
The transfer function is 1 V = 1 mA, with a maximum adjustment of 2.5 V
or 2.5 mA.
When operating in ACC the PLIM (power limit) function is still active if the
MPD current reaches the limit point. This is especially helpful if the laser
is to be operated at varying temperatures where the efficiency may
change to the point where the operating current will overdrive the laser.
The PLIM will always keep the laser in a safe operating area when
properly set.
If no MPD is connected always set the PLIM ADJ fully clockwise.
6. The P/I ADJ Pot will allow adjustment of the laser drive current from 0 mA
to the ILIM set point or 500 mA max. When turning on a laser for the first
time it is suggested that this pot be set fully counter-clockwise.
7. Press and release the ENABLE switch.
8. The green LD ON indicator will turn on.
Note:
There will always be a delay until full power of approximately 2 to
3 seconds before any current can flow to the laser diode.
9. Adjust the P/I ADJ potentiometer clockwise to increase the injection
current of the laser diode. The Ild Test point provides an analog read back
of the actual laser current, 1 V = 1 A. The Ipd Test point provides an
analog read back of the photodiode monitor current, 1 V = 1 mA and can
be used to gauge the relative output power of the laser.
10. Pressing the ENABLE switch while the laser is operating will turn off the
laser current.
