IC-WKN_14 Datasheet, PDF (9/12 Pages) IC-Haus GmbH – 15 V CW LASER DIODE DRIVER

iC-WKN
15 V CW LASER DIODE DRIVER
SAFETY PRECAUTIONS
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 C1, Page 9/12
FUNCTION DESCRIPTION
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 LDA.
5V
4V
3V
2V
1V
0
V(VCC)
5V
4V
3V
2V
1V
0
V(LDA)
400 mV
300 mV
200 mV
100 mV
V(MDA)
1V
500 mV
0
V(CI)
60 m
40 m
20 m
0
I(LDK)
0
Phase I Phase II Phase III
10 us
20 us
Time
30 us
40 us
50 us
Figure 1: Turn-on behaviour
A quick soft-start follows during phase I; the control
capacitor CI is charged at an accelerated rate until the
voltage at pin MDA reaches 1/3 of its nominal value.
With V (MDA) > 1/3 V (MDA)_nom phase II starts, the
controlled start-up. The transition to CW operation
(phase III) 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.
Turn-off behaviour
iC-WKN works without a fixed undervoltage lockout,
thus the laser diode forward voltage is the prime fac-
tor determining the lowest possible supply voltage.
If the voltage drops below this value, the output driver
is forcibly saturated and the laser current decreases.
iC-WKN simultaneously discharges the control capac-
itor CI so that no excessive laser diode currents occur
when the supply voltage rises again.
5V
4V
3V
2V
1V
0
V(VCC)
5V
4V
3V
2V
1V
0
V(LDA)
400 mV
300 mV
200 mV
100 mV
V(MDA)
1V
500 mV
0
V(CI)
60 m
40 m
20 m
0
I(LDK)
100 us
Phase IV Phase V
110 us
120 us
Time
130 us
140 us
150 us
160 us
Figure 2: Turn-off behaviour
Disruptions in operation
The power control is shut down with excessive driver
temperature or when the laser current reaches the
overcurrent shut-down threshold, for example when
the feedback is interrupted. If the monitor diode or the
bias resistor RM fail, the device is shut down in less
than 250 µs, provided that the supply voltage applied
is high enough. When modulating the laser current via
pin MDK, excessive voltage occurring at pin MDA also
may cause a shut-down.