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O P E R A T I O N
2
C H A P T E R
Installation
terminals. When disconnecting devices, it is only necessary to turn the OUTPUT
off.
System Interlock
When the LDX-3412 is shipped, an interlock is incorporated at connector J105
(pins 1 and 2). Output current will not flow unless there is an electrical connection
made between pins 1 and 2 of J105.
When the interlock function is to be used, the user must provide a normally closed
switch or relay across pins 1 and 2 of the 9-pin connector (J105). The switch must
be electrically isolated from all other circuits, including earth ground.
Photodiode Feedback Connections
The 9-pin connector J105 (see pinout, Figure 2.3) on the rear panel contains the
current supply output and earth ground. The photodiode feedback signal is input
at the connector at pins 6 and 7.
Many laser diode modules contain an internal photodiode that monitors the back-
facet emission of the laser. This photodiode is usually internally connected to
either the laser anode or cathode. Figures 2.5 A - D show the recommended
connections and shielding for the various configurations of laser diode modules
and photodiode feedback schemes.
The feedback photodiode reverse-biasing supply shown in these figures must be
supplied by the user. You must locate this supply where it won't cause the
common mode voltage of the feedback inputs to exceed the specified maximum of
+6 V, relative to the "-" current output (J105, pins 4,5). Noise from this biasing
supply may contribute to the output noise levels; therefore, a battery with shielded
connections is recommended.
8
LDX-3412
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OUTPUT
P. D.
L. D.
Figure 2.4 Common Laser Cathode - Photodiode Cathode
Module
7
+
Bias
6
+
-
9
5
3
Earth Ground
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