iC-WJ, iC-WJZ
LASER DIODE DRIVER
Rev A1, Page 9/12
CW OPERATION
In case of CW operation, the input IN can be connected to the power supply VCC. The pin CWD may be
unloaded, because the capacitor for the watchdog is not necessary. The capacitor CI for the averaging control
can be reduced to 100nF.
Fig. 10: CW operation via cable
Operation of laser diode via cable
It is recommended to connect a capacitor from 1nF up to 10nF across the laser diode in order to protect the
laser diode against destruction due to ESD or build-up transients. This capacitor should be placed close to the
laser diode and not at the entry of the LD supply line.
An approx. 12Ω series resistor at pin KLD reduces the IC power consumption and damps possible resonances
of the load circuit caused by the inductive LD supply line. This resistor is useful for many applications, also for
those which do not operate via cable.
When the LD supply line is printed on the PCB, the forward path VCC should be arranged in parallel with, i.e.
be close to the return path to KLD, even when the line is only a few centimeters in length.
Analog modulation during CW operation
The modulation cut-off frequency is determined by the capacitor CI as well as by the operating point set with
the resistor RSET. With CI= 100nF and RSET= R2= 10kΩ the cut-off frequency is approx. 40kHz, with CI=
22nF and the same resitor value of about 230kHz.
Fig. 11: Analog modulation during CW operation
ROITHNER [ Roithner LaserTechnik GmbH ]
