IC-WKM_15 Datasheet, PDF (9/12 Pages) IC-Haus GmbH – M-TYPE CW LASER DIODE DRIVER

iC-WKM
M-TYPE CW LASER DIODE DRIVER
SAFETY INSTRUCTIONS
Laser light can damage the human eye and the
eyes of animals! Do not look at any laser light di-
rectly or through any optical lens. When handling a
laser diode, do not look directly at the light generated
by it. Wear appropriate safety glasses to prevent light
from entering the eye even by reflection.
Rev C2, Page 9/12
FUNCTION DESCRIPTION
Setting the output power
The output power is simply set by RM = V(MDA) / I(MD);
with V(MDA) = Item-No. 101 and I(MD) = monitor cur-
rent of the laser diode at the desired operating point.
RM should be combined from fixed resistor (max. output
power) and a trimmer (calibration).
Turn-on behaviour
After switching the supply voltage on, the output stage
remains disabled until the internal enabling flip-flop is
set by a sufficiently high voltage at VCC.
A quick soft start follows; the transition to controlled CW
operation is gradual and primarily determined by the
values of CI and RM. CI is properly dimensioned when
the voltage overshoot at MDA is at a minimum.
V(MDA)
200mV
100mV
0
−100mV
V(LDA)
1,5V
1,0V
500mV
0
V(CI)
2V
1V
0
I(LD)
200mA
100mA
0
0
50us
100us
Time 150us
200us
250us
Figure 1: Turn-on behaviour
If the voltage drops below this value, the output stage
is forcibly saturated and the laser current decreases.
iC-WKM simultaneously discharges the control capaci-
tor CI so that no excessive laser diode currents occur
when the supply voltage rises again.
V(MDA)
200mV
100mV
0
−100mV
V(LDA)
1,5V
1,0V
500mV
0
V(CI)
2V
1V
0
I(LD)
200mA
100mA
0
1000us
Time
1,01ms
Figure 2: Turn-off behaviour
1,02ms
Disruptions in operation
The power control is shut down with excessive driver
temperature or when the laser current reaches the over-
current shutdown threshold, for example when the feed-
back is interrupted. If the monitor diode or the bias
resistor RM fail, the device is shut down in less than
600 µs, provided that the supply voltage applied is high
enough.
Turn-off behaviour
iC-WKM works without a fixed undervoltage lockout,
thus the laser diode forward voltage is the prime factor
determining the lowest possible supply voltage.
When modulating the laser current via pin MDK, exces-
sive voltage occurring at pin MDA also may cause a
shutdown.