External Current Control - THORLABS MLDEVAL User Manual

current to lower value, please see the recommendations given in section
tion !
4

5.1 External Current Control

As described in the previous section, the potentiometer P2 is used for adjusting the laser cur-
rent of the MLD203CHBE or MLD203CLNE module. Using P2, the control voltage at the I
put of the MLD203CxxE module can be changed between 0 and the internal reference voltage
V (2.5 V DC).
REF
The same can be achieved from an external voltage source.
Attention
The external voltage must not exceed the range from 0 to +2.5 V DC in order to avoid damage
to the MLDEVAL and the MLD203PxE!
1. Set the mode switches SW4.1 to 4.2 (4):
SW4.1 Pset / Iset
SW4.2 Mod. In
SW4.3 Comp
SW4.4 Comp
2. Connect the external voltage source via the Mod. In SMA connector (11). Set the output
voltage of the external source to 0.
3. Insert the MLD203CHBE or MLD203CLNE into the sockets J8/J9 (3). Make sure that the
white triangle matches with pin 1 of the adapter PCB.
4. Connect the laser diode as described in topic 4 on
5. Make sure that SW1 (9) is set to off.
6. Connect the power supply (external 5 V DC via or a USB power) to the MLDEVAL.
7. The laser diode current can be monitored at the J6 Mon. Current Connector (13) by meas-
uring the voltage at this connector. The conversion coefficient is 1 V/A, so the current is cal-
culated by
8. Set SW1 (9) to ON. The green LED1 next to SW1 lights up.
9. Now, the external control voltage can be changed within the range from 0 to +2.5 V.
Warning
Make sure you observe the laser current while applying a modulation signal! At an input voltage
of 2.5 V (= offset voltage plus amplitude), the laser current will reach the maximum value of 200
mA! In the case you need to limit the laser current to lower value, please see the recommenda-
tions given in section
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Laser Current Limitation
5 Operating a MLD203CxxE Module (CC)
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Laser Current Limita-
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