PLD datasheet(15/21 Pages) WAVELENGTH

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PLD 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 PLD driver.

Figure 15 illustrates a simple

circuit.

ANALOG

INPUT

COMMON

Keep R1 and R2 below 100 kΩ

for maximum accuracy.

R2 + R1

New

Transfer

Function

Old Transfer Function

Example:

(for PLD-200)

R1 = 9 kΩ

R2 = 1 kΩ

1 + 9

New

Transfer

Function

40 mA / V = 4 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.

Analog Input

Pin 12

V+5V

Common

Pin 6

* Use an LM4040-2.5 with a +5 V supply for a

0 to 2.5 V external setpoint signal

* V

+5V must be at least 1 volt greater than the voltage value of D1.

+5V = Supply voltage (5 to 30 V)

D1 = Bandgap reference * (LM4040D50)

R1 = 2.2 kΩ, 1 W resistor

R2 = Trimpot, 10 kΩ to 100 kΩ

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 PLD and laser.

It is critical that the PLD Driver is properly

grounded. If the PLD Driver is used with a

WavelengthElectronicstemperaturecontroller,

youmayneedtousetwoseparatepowersupplies

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.

GROUND THE FAN ON THE PLD1250,

PLD5000, AND PLD6500

The PLD1250, PLD5000, and PLD6500 models are

equipped with a fan that cools the heatsink. The fan in some

cases may create electrical noise. To reduce the electrical

noise level you must connect the heatsink to earth/chassis

ground or the system ground (power supply common). To

ground the heatsink you need to connect ground to the

tapped hole in the bottom of the heatsink.

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 330 µF,

16 V electrolytic capacitor between the power terminals

(pins 10 and 11). This decoupling capacitor should be

directly connected at the driver.

PLD Datasheet(PDF) 15 Page - Wavelength Electronics, Inc.

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