CWD-01-V2-D Analog Technology, Inc., CWD-01-V2-D Datasheet - Page 3

• Manufacturer Part Number: CWD-01-V2-D
• Description: Constant Current Cw Laser Driver
• Manufacturer: Analog Technology, Inc.

APPLICATIONS
Figure 4 shows a typical stand-alone application circuit.
Figure 5 shows a typical micro-processor-based application
circuit.
In Figure 4, the switch S1 is external shut down switch, it
can turn on and off the controller with the SDN pin high
and lower respectively, at the internal chip control input:
>1.4V = enable, <0.95V = shut down, normal threshold
voltage = 1.2V. The switch S1 can also be an electronic
switch, such as an I/O pin of a micro-controller, with an
either open drain or push/pull output. See Figure 5. If not
using a switch (S1) to control the laser, leave the SDN pin
unconnected.
In Figure 4, the LED D1 is used to indicating laser diode
status. When LDGD pin is high, >2V, the laser diode
control loop is working properly. When LDGD pin is low,
<0.3V, the laser diode is bad, or there is a short or open
circuit at the laser diode. The LDGD pin can also be
connected to a digital input pin of a micro-controller, when
software/firmware is utilized in the system. See Figure 5.
In Figure 4, the adjustable resistor W1 is used to setting the
output current. Setting LIS from 0V to 2.5V will set the
laser current from 0A to 2A linearly.
The laser diode D2 is connected between LDA and PGND.
It is worth mentioning that the power supply return
terminal should be connected to the pin 11 PGND and the
cathode of the laser diode should be connected to the pin
10 PGND. These 2 nodes should not be connected together
externally and they are connected together internally
already by the controller.
Turning the Controller On and Off
The controller can be turned on and off by setting the SDN
pin high and lower respectively. It is recommended to turn
the controller on by this sequence:
To turn on: turn on the power by providing the power
supply voltage to the controller, turn on the controller by
releasing the SDN pin.
To turn off: turn off the controller by lowering the voltage
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To DC voltmeter
Figure 4 A Typical Stand-alone Application Schematic
1 W1 100K
K
S1 Shutdown
D1
(Clock-wise)
Analog Technologies
LED
A
3
1
2
3
4
5
6
SDN
LDGD
GND
2.5VR
LIS
LIO
CWD-01-V2-D
PGND
PGND
LIGD
GND
LDA
VPS
12
11
10
9
8
7
D2
A
+5V
To power GND
To DC voltmeter
To signal GND
Laser diode
K
Constant Current CW Laser Driver
To micro-controller
To micro-controller
of SDN pin, turn off the power by stopping the voltage
supply on the VPS pin.
When not controlling by the SDN pin: leave it unconnected
and turn on and off the controller by the power supply.
Adjusting the Output Current
The output current is set by adjusting W1, which sets input
voltages of LIS, pin 5. See Figure 4. The output current
will be:
I_output = 2.0 × V
LIS can be configured by using a DAC, to replace the W1
in Figure 4. Make sure that the DAC has output low noise,
or, if no modulation is needed, an RC low pass filtered by
be inserted between the DAC and the LIS pin. See Figure 5.
The LIO can still be used to monitor the output current
when the LIS is adjusted. 0V to 2.5V indicates the laser
current of from 0A to 2A linearly.
Monitoring the Output Current
The output current of the controller can be monitored by
measuring the voltage on the LIO pin. This feature is very
useful for miro-controller based system where the ADC is
available and monitoring the current in real time is
required. This pin provides a very low noise voltage signal
which is proportional to the output current:
LIO (V) = 2.5 × I_output/2.0 (V).
For example, when the output signal equals to 2.5V, the
output current is 2A.
LIO can be used to drive an ADC directly, and also be
measured by a multimeter during debugging process.
Controller Power Consumption
The power consumption of the controller can be calculated
by:
P_controller = I_input × V
where I_output is the output current;
I_input is the power supply intput current;
To ADC & DAC
Figure 5 A Typical Micro-processor-based Application
To signal GND
To DAC
To ADC
LIS
1
2
3
4
5
6
/2.5 (A).
SDN
LDGD
GND
2.5VR
LIS
LIO
CWD-01-V2-D
PS
– I_output × V
CWD-01-V2-D
PGND
PGND
LIGD
GND
LDA
VPS
12
11
10
9
8
7
LDA
A
D2
,
+5V
To power GND
To ADC
To signal GND
Laser diode
3
K