iC-WKP
15 V CW P-TYPE LASER DIODE DRIVER
Rev A6, Page 6/10
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.
FUNCTION DESCRIPTION
Setting the output power
The output power is simply set by RM = Vref(MDK) /
I(MD), where Vref(MDK) = Item No. 101 and I(MD) =
the monitor current of the laser diode at the desired
operating point. RM should be combined from a fixed
resistor (max. output power) and a trimmer (calibra-
tion).
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 undershoot at MDK is at a minimum.
V(MDK)
VCC
VCC − 0.5V
VCC − 1V
VCC − 1.5V
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
If the voltage drops below this value, the output stage
is forcibly saturated and the laser current decreases.
iC-WKP simultaneously discharges control capacitor
CI so that no excessive laser diode currents occur
when the supply voltage again rises.
V(MDK)
VCC
VCC − 0.5V
VCC − 1V
V(LDA)
1.5V
1.0V
500mV
0
V(CI)
2V
1V
0
I(LD)
200mA
100mA
0
1ms
Time
1,01ms
1,02ms
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 shutdown threshold, for example when the
feedback path is interrupted. If the monitor diode or
bias resistor RM fail, the device is shut down in less
than 600 µs, provided that the supply voltage applied
is high enough.
When modulating the laser current via pin MDA, low
voltage occurring at pin MDK may also cause a shut-
down.
Figure 1: Turn-on behaviour
Turn-off behaviour
iC-WKP works without a fixed undervoltage lockout,
thus the laser diode forward voltage is the prime fac-
tor determining the lowest possible supply voltage.
ICHAUS [ IC-HAUS GMBH ]
