THORLABS LD2000R, Руководство пользователя

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OEM Laser Diode Driver Chapter 5: Operating the LD2000R
Rev I, May 21, 2018 Page 9
Pin Name Description
1 CX1 These pins are provided for connecting an external capacitor to
the control loop integrator to extend the integrator time constant.
This may be necessary to get maximum bandwidth when using
TTL modulation. Connect the positive terminal of the cap to CX2.
2 CX2
3
Analog
Modulation
This pin is used with an external voltage signal source to provide
analog modulation. The transfer function (referenced to the
photodiode current) is -50 µA/V with 0 V being the laser
completely on. The laser output decreases as this voltage
increases with the laser being completely off at 2.5 V. Connect
this pin to ground when not using the analog modulation.
4 Slow Start
This output pin is high during the startup period and goes low
when the laser is enabled. It can be used as a LASER
EMISSION indicator. An external capacitor can be connected
from this pin to ground to extend the slow start delay time.
Note: this output will not drive an LED directly and must be
buffered. Contact Tech Support for more details.
5
PD Current
Trimpot
This pin is connected to the wiper of the on-board PD Current
Trimpot. Connect this pin to the PD Current Setpoint to control
the PD current with the on-board trimpot.
6
PD Current
Setpoint
This pin controls the PD Current according to a transfer function
of 50 µA/V with 0 V being the laser is completely off (0 PD
current). The laser output increases as this voltage increases.
7 REF Out This is a buffered 2.5V voltage reference.
8 PD AMP Out
This is an analog voltage proportional to the photodiode current
and referenced to one half the supply voltage as follows:
𝑉
𝑃𝐷 𝐴𝑚𝑝
=
𝑉
+
2
− 𝑅
𝐹
(𝐼
𝑃𝐷
)
,
where R
F
= PD Amp Transimpedance gain (internal 20 k

in
parallel with R
F EXT
)
9 V
+
Positive supply voltage (8 to 12 VDC).
10 GND Power supply common.
11 LD A/PD K Common laser diode anode, photodiode cathode.
12 PD A Photodiode anode.
13 LD K Laser diode cathode.
14
Limit
Setpoint
This voltage determines the maximum laser drive current
according to the transfer function 40 mA/V.
15 Limit Trimpot
This is connected to the wiper of the Limit Current trimpot.
Connect this to the Limit Setpoint pin to use the on-board trimpot
to set the current limit.
16 Not used This must be tied to ground to operate the laser.
17 ON/OFF
This pin is used to externally turn the laser on and off through
the slow start circuit and to set the low voltage dropout point. It
has an internal 20 k
Ω resistor to ground. Connect a 15 kΩ
resistor to the power supply voltage to set the dropout voltage to
4.5 V.
18 Limit Out
This is an output voltage proportional to the limit current with a
transfer function of 40 mA/V. Use this pin to assist in setting the
laser current limit.