Wavelength Electronics LDTC0520, Техническое описание и руководство по эксплуатации

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LDTC0520 / LDTC1020 LASER DIODE AND TEMPERATURE CONTROLLER
SET CONSTANT POWER OR CONSTANT
CURRENT CONTROL MODE
Refer to Figure 12 , and set the mode switch for Constant
Current or Constant Power mode: the mode switch is the
center DIP switch, labeled “CC | CP”. For Constant Current
mode operation, set the switch to INT (down); for Constant
Power mode, set the switch to EXT (up).
!
Do not adjust the CC | CP switch while the
output is enabled and driving a laser diode.
The laser diode may be damaged or destroyed.
In CC mode, the setpoint voltage correlates directly to the
laser diode current. In CP mode the setpoint correlates to
the photodiode feedback current. Table 2 on page 5
gives the transfer functions for CC and CP mode.
SET THE DRIVER FOR ONBOARD OR
EXTERNAL SETPOINT CONTROL
Next, set the reference source for the laser current setpoint.
To use the onboard ISET trimpot to control the laser current
setpoint (Constant Current mode) or the laser power
(Constant Power mode),
1. Set the LDREF DIP switch to INT (down).
2. Ensure that LD SHD (pin J2‑3) is tied to ground (either
directly, or using an external signal).
To use an external setpoint signal,
1. Set the LDREF DIP switch to EXT (up).
2. Connect the signal source to EXT LD SETpoint (pin
J2‑5). Note that this signal
does not
sum with the
onboard trimpot.
3. Ensure that the LD SHD (pin J2‑3) is tied to ground
(either directly, or using an external signal).
!
Do not adjust the LDREF switch while the
output is enabled and driving a laser diode.
The laser diode may be damaged or destroyed.
ADJUST THE LASER OUTPUT SETPOINT
If the LDTC is configured for onboard laser control, the
septoint is adjusted using the ISET trimpot, accessible
through the hole in the front cover.
If the LDTC is configured for external setpoint control,
connect the signal source to Pin J2‑5. Example
setpoint circuits are shown on page 19 , and the
transfer function for the EXT LD SET input is shown in
Table 2 .
EXTERNAL OR ONBOARD LD CURRENT
ENABLE
The laser output enable can be controlled from the onboard
switch, or by an external signal. If the external signal is used,
the onboard switch must be set to EN (enabled).
Both the external enable signal (at Pin J2‑3) and the onboard
enable switch must be set to ENABLE for the LDTC to drive
current to the laser.
Pin J2‑3 is TTL‑compatible. Ground corresponds to enable,
while open or a 3 to 5 V signal corresponds to disabled.
MONITOR LASER DIODE AND PHOTODIODE
CURRENT
Connector J2 includes monitors for laser forward current
and photodiode current. Pin J2‑8 is LD I Mon and pin J2‑7
is LD P Mon.
The LD I Mon pin outputs a voltage proportional to the laser
diode forward current according to the transfer functions
listed in Table 2 .
Both monitor signals are available at all times, regardless of
whether the driver is operating in CC or CP mode.
The LD P Mon pin outputs a voltage proportional to the
photodiode current; refer to Table 2 for the transfer function.
The standard maximum photodiode current is 2 mA. The
photodiode current range can be changed by replacing a
1206-sized surface-mount resistor on the circuit board;
contact the factory for assistance.