Wavelength Electronics WLD3343, Manual

Page: 16 / 18

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WLD3343
PAGE 16
WLD3343-00400-O
OPERATION
9. CONTROLLING THE LASER
DIODE FORWARD CURRENT IN
CONSTANT CURRENT MODE
Equation 5 calculates the laser diode forward
current produced by applying a voltage at Pin 2
(V
SET
) in constant current mode.
10. CONTROLLING THE MONITOR
PHOTODIODE CURRENT IN
CONSTANT POWER MODE
Equation 6 calculates the monitor photodiode
current produced by applying a voltage at Pin 2
(V
SET)
in constant power mode.
11.TYPICAL OPERATION OF THE
VOLTAGE CONTROL INPUT
Figure 11 illustrates a typical con fi guration of the
WLD3343 voltage input.
CAUTION: CONNECTING VOLTAGES
OUTSIDE THE RANGE OF VDD TO GND TO
THE VOLTAGE SETPOINT INPUT ON PIN
2 (V
SET
) CAN RESULT IN DAMAGE TO THE
WLD3343 OR YOUR LASER DIODE.
12. MEASURING LASER DIODE
FORWARD CURRENT USING THE
CURRENT MONITOR OUTPUT
Equation 7 provides a transfer function for
converting the voltage output of Pin 3 (IMON) to
the amount of forward current
fl owing through the
laser diode.
13.MEASURING MONITOR
PHOTODIODE CURRENT IN
CONSTANT CURRENT MODE
Equation 8 provides a transfer function for
converting the voltage across R
PD
to the
amount of current fl owing through the monitor
photodiode in constant current mode.
14. MEASURING MONITOR
PHOTODIODE CURRENT IN
CONSTANT POWER MODE
USING THE POWER MONITOR
OUTPUT
Equation 9 provides a transfer function for
converting the voltage output of Pin 4 (PMON)
to the amount of current
fl owing through the
monitor photodiode in constant power mode.
Figure 11
Con fi guring The Voltage Input
Equation 5
Constant Current Control
Equation 8
Monitor Photodiode Current Measurement in
Constant Current Mode
Equation 7
Laser Diode Forward Current Measurement
Equation 6
Constant Power Control
Equation 9
Monitor Photodiode Current Measurement in
Constant Power Mode
ILD
V PIN2
2*RSENSE
[AMPS]
=
IPD
V PIN2
2*R
[AMPS]
=
PD
IPD
VR
[AMPS]
=
PD
R PD
IPD
V PIN4
[AMPS]
=
R PD 2*
GND
7
WLD3343
2
V
SET
2 k
:
1 k :
DC BIAS
TRIMPOT
2.5 V
Bandgap
Voltage
Reference
V
PIN2
V
DD
OR OR
+
ILD
V PIN3
2*R
[AMPS]
=
SENSE