IC-WKP Datasheet, PDF (7/10 Pages) IC-Haus GmbH – 15 V CW P-TYPE LASER DIODE DRIVER

iC-WKP
15 V CW P-TYPE LASER DIODE DRIVER
APPLICATION NOTES
Rev A6, Page 7/10
Laser diode types
Two laser diode types can be operated by iC-WKP.
The operation of N-type laser diodes it is also possible.
Here, however, the current mirror at MDA introduces a
certain error to the automatic power control (c.f. Elec-
trical Characteristics Nos. 108–110); iC-WKN, which
has been optimised for use with these diodes, may be
a better choice.
iC-WKP does not allow for the operation of M-Type
laser diodes. For these laser diode types iC-WKM
would be the best choice.
Figure 3: Operation of a P-type laser diode
As iC-WKP has been optimised for use with P-type
laser diodes, it is with this type of diode that the best
functionality is achieved. This type of setup also en-
ables the laser diode package to be connected to GND.
Layout
To prevent instability of the regulator an additional ca-
pacitor (ca. 100 pF) must be positioned directly at the
iC’s pin CI. Depending on the laser diode, capacitor
CM with typ. 2 nF in parallel with RM may be required
for stability. RL may be introduced to improve stability
even further and additionally reduce the power dissi-
pation of iC-WKP.
Pin AGND acts solely as a ground reference for the
power regulator (CI and RM) and should not be short-
circuited with GND externally. This could have a neg-
ative effect on the control behaviour and monitor func-
tions.
Figure 4: Operation of an N-type laser diode
Cooling
Laser diodes should be sufficiently cooled, particularly
with the power-regulated operation of setups which
use iC-WKP, for example. The power dissipation in the
laser diode otherwise causes the diode to heat up and
the level of efficiency to drop which the power control
unit then compensates for by increasing the laser cur-
rent. This in turn brings about a rise in power dissipa-
tion in the laser diode and thus also in temperature. In
this instance the laser diode could be damaged (result-
ing in spottiness of the laser beam and an increase in
operating current) or even destroyed before the over-
current shutdown threshold in iC-WKP is reached.