Wavelength Electronics PLD K-CH Series, Datasheet And Operating Manual

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PLDXK-CH SERIES LASER DIODE DRIVER
CHANGE THE ANALOG INPUT MODULATION
TRANSFER FUNCTION
The analog input modulation transfer function can be
changed by adding a voltage divider resistor network
external to the PLDxK-CH driver. Figure 15 illustrates a
simple circuit.
R2
ANALOG
INPUT
V
COMMON
Keep R1 and R2 below 100 k Ω
for maximum accuracy.
IN
R1
R2 + R1
R2
New
Transfer
Function
Old Transfer Function = *
Example:
(for PLD10K-CH)
R1 = 9 k Ω
R2 = 1 k Ω
1 + 9
1
New
Transfer
Function
2.3 A / V = 230 mA / V = *
Figure 15. Changing the Analog Input
Modulation Transfer Function
EXTERNAL SETPOINT CIRCUIT
An external trimpot circuit can be used to adjust the laser
current setpoint; refer to Figure 16 .
R1
R2 D1
Analog Input
Pin J3:5
V
+5V
Common
Pin J3:1
= Supply voltage (5 to 30 V)
D1 = Bandgap reference* (LM4040)
R1 = 2.2 kΩ, 1 W resistor
R2 = Trimpot, 10 kΩ to 100 kΩ
* must be at least 1 volt greater than
the voltage value of D1.
V
+5V
V
+5V
Figure 16. Trimpot Circuit for Analog Input
IMPORTANT INFORMATION ON GROUNDING
Some laser diodes connect the laser anode or cathode to
the case. In such cases special attention must be paid to
grounding to ensure safe operation of the PLDxK-CH and
laser.
!
It is critical that the PLDxK-CH Driver is
properly grounded. If the PLDxK-CH Driver
is used with a Wavelength Electronics
temperature controller, you may need to
use two separate power supplies that float
independently of each other.
If the laser anode is connected to the laser case, it is possible
that the anode will be connected to earth ground when
the laser is installed in a benchtop mount or in your laser
system. In situations where the laser diode is connected to
the case, it is critical that the negative terminal of the power
supply remain isolated from earth ground.
FINE TUNE DEEP MODULATION
If the analog modulation input is near the rail (> 4.5 V), output
current signal response may be insufficient. Performance
may be improved by connecting a quality low-ESR 470 µF,
16 V electrolytic capacitor between the power terminals
(pins H1:1 and H1:2). This decoupling capacitor should be
directly connected at the PLDxK-CH.
PLD5K-CH AND PLD10K-CH REVISION A
Revision A of the PLD5K-CH and PLD10K-CH use a
different connector configuration than later revisions.
Figure 17 shows the connector configuration.
LD Cathode
LD Anode
PD Cathode
PD Anode
J1
+5V
LD Cathode
LD Anode/LD Supply
Ground
PD Cathode
PD Anode
+5V
Figure 17. Revision A Connector
PLD5K-CH and PLD10K-CH