© 2001, 2003, 2009
WLD3393
PAGE 4
WLD3393-00400-A Rev F
CONFIGURING THE DEMO BOARD
STEP 2: CONFIGURE FOR CONSTANT CURRENT OR CONSTANT POWER MODE
The two modes of operation supported by the WLD3393 are constant current and constant power
mode.
It is very important to note that the WLD3393 should be confi gured for either constant
current or constant power mode BEFORE power is applied. Changing operating mode while
the WLD3393 is operating can result in damage to your laser diode.
In constant current mode,
V
Set
correlates directly to the laser diode current, regardless of laser diode power intensity. In constant
power mode, the WLD controls the laser diode using the photodiode to achieve a laser intensity that
is directly proportional to V
Set
.
Constant Current mode
ignores the laser’s photodiode. The WLD3393, however, is designed to allow
you to monitor the laser’s photodiode while running in this mode. Monitor the voltage at the PDM pin on
the terminal block on the top side of the WLD3393. Before powering the unit on to operate in constant
current mode, make sure that the mode switch is in the CC position (see Figure 1). Select the output
current range by setting the LD RANGE jumper on the back of the WLD3393 to either the 200mA or
the 2A position. See Figure 4 for location.
Constant power mode
utilizes the laser’s photodiode to regulate the intensity of the laser in proportion
to V
Set
. While the unit is NOT powered, make sure the mode switch is in the CP position to confi gure the
WLD3393 for constant power mode (see Figure 1). Set the PD RANGE jumper on the bottom of the
WLD3393 to either the 200
μ
A or the 2mA range, depending on the specifi cations of your photodiode.
See Figure 6 for the location of the PD Current Range jumper. It is important to make sure that
the correct PD current range is selected as the WLD3393 may overdrive the laser if the PD range
is confi gured incorrectly, resulting in permanent damage to the laser. Use the LD RANGE jumper to
select between the 200mA and 2A range based on the rating of the laser load. See Figure 4 for the
location of this jumper.
Figure 4: Bottom View, Jumper Locations
VSET
SOURCE
JUMPER
LD RANGE
JUMPER
PD RANGE
JUMPER
