LDTC 2SLASH2O datasheet(13/25 Pages) WAVELENGTH

13 / 25 page

www.teamWavelength.com

LDTC2/2 LASER DIODE DRIVER AND TEMPERATURE CONTROLLER

CONFIGURE THE LASER DIODE CURRENT LIMIT

The default configuration of the LDTC2/2 uses a trimpot

to adjust the Current Limit. The trimpot is labeled ILIM (as

opposed to LIM A or LIM B for the temperature control limit

current trimpots). Fully CCW sets the limit current to the

maximum. A simulated laser diode load is recommended to

set the limit current. To set the laser diode current limit:

• Configure for local operation by installing the VSET

jumper to the lower position (see

Figure 10).

• Set ILIM to zero by turning the trimpot 12 full turns CW.

• Set ISET to maximum by turning the trimpot 12 full turns

CW.

• Monitor the voltage between LD I MON and COM.

• Increase ILIM (turning CCW) until the desired voltage is

reached.

• Decrease ISET (turning CCW) until the voltmeter is

affected, then stop.

The LD current limit is now set and the current can be

adjusted within the limit range.

LASER DIODE SETPOINT AND MODULATION

The laser diode setpoint voltage determines the amount of

current that is delivered to the laser. In Constant Current

mode, the setpoint is directly proportional to the laser diode

current. In Constant Power mode, the setpoint is directly

proportional to the photodiode current, allowing for control

of the optical power of the light emitted by the laser diode.

The setpoint voltage can be adjusted either by using the on-

board ISET trimpot, by applying an external setpoint voltage,

or by summing an external setpoint voltage with the setpoint

voltage created by adjustment of the ISET trimpot. The sum

of the external setpoint voltage and the voltage created with

the on-board ISET trimpot can be from zero to 2.5 V.

To use only the on-board ISET trimpot, place the VSET

jumper in the lower position (as shown below in

Figure 10),

and do not connect an external voltage source to the R LD

SET input. The ISET trimpot provides a setpoint adjustment

of between zero to 2.5 V.

Use On-board

trimpot

Sum ExtTset with

trimpot

Use External

Voltage only

ExtTset Vset PDset

Figure 10. Laser Diode Setpoint Configuration

To use an external voltage source summed with the voltage

supplied by the ISET trimpot, place the VSET jumper in the

lower position (as shown in

Figure 10). Connect the external

voltage, or DAC output, to the R LD SET input (Pin 5 on

Connector J2). The final setpoint voltage will be the sum of

the external voltage being supplied plus any setpoint voltage

created with the on-board SET trimpot.

To use only an external voltage source for the setpoint

voltage, place the VSET jumper in the upper position (see

Figure 10) and connect the external setpoint voltage via the

R LD SET input. In this configuration, any voltage created

by the on-board ISET trimpot will not be included in the final

setpoint voltage which is applied to the laser driver.

Equation 4 illustrates the relationship between setpoint

voltage (V

R LD SET) and the current that will be applied to the

laser diode.

Equation 4. Current Applied to the Laser Diode

LD = 1.25 · VR LDSET

Equation 5 and Equation 6 illustrate the relationship

between setpoint voltage (V

R LD SET) and the resulting

photodiode current while operating in Constant Power

mode for the two standard photodiode ranges that can be

configured on the LDTC2/2.

Equation 5. Photodiode Current in Constant Power Mode

(2 mA PD Range)

PD = 0.001 · VR LDSET

Equation 6. Photodiode Current in Constant Power Mode

(200 μA PD Range)

PD = 0.0001 · VR LDSET

OPERATION NOTES

MODULATION CAUTION: If operating with VDD

at 12 V and you exceed 12 V on R LD SET with

the modulation signal for any duration, the

WLD will be destroyed

WARNING: The LDTC2/2 does not support

laser diode packages that incorporate a built-

in sensor that is connected to or common

with the laser case ground.

LDTC 2/2O Datasheet(PDF) 13 Page - Wavelength Electronics, Inc.

LDTC 2/2O Datasheet(HTML) 13 Page - Wavelength Electronics, Inc.

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Datasheet Download

Link URL