iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev A1, Page 6/12
APPLICATIONS INFORMATION
Laser Power Adjustment
The iC-WJ and iC-WJZ devices can be adapted to CW laser diodes from 2 to 40mW. Models can be used in
which the cathode of the monitor diode is connected to the anode or the cathode of the laser diode.
The pin ISET is used for the adjustment to the sensitivity of the monitor diode and to set the desired optical
laser power. The setpoint for the averaging control of the monitor diode current is preset at this pin.
Fig. 1: Operation of a laser diode according to the example
To calculate the current required at ISET, the average optical laser power is to
determine:
P
av
P
peak
×
t
whi
T
with peak value P
peak
and pulse/period duration t
whi
/T
Fig. 2
Example iC-WJ:
Laser diode with 5mW maximum optical output, monitor diode with 0.13mA/mW, pulse duty
factor set to 20% with P
peak
= 5mW:
The resultant average optical power is 1mW and the average monitor diode current is 0.13mA. The resistor
RSET is calculated as:
RSET
CR1 V
(ISET)
I
av
(AMD)
1 1.22V
≈
9.4k
Ω
0.13mA
with the Electrical Characteristics No. 301 for V(ISET)
and with No. 108 for current ratio CR1
Example iC-WJZ:
Laser diode with 5mW maximum optical output, monitor diode with 0.75mA at 3mW, CW
operation (pulse duty factor 100%) with P
cw
= 1mW:
For the monitor diode current of 0.25mA the resistor RSET is calculated as:
RSET
CR1 V
(ISET)
I
av
(AMD)
3 1.22V
≈
14.6k
Ω
0.25mA
with Electrical Characteristics No. 301 for V(ISET) and
with No. 108 (iC-WJZ) for current ratio CR1
ROITHNER [ Roithner LaserTechnik GmbH ]
