LDTC-LAB datasheet(9/31 Pages) WAVELENGTH

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THEORY OF OPERATION

The LDTC LAB Series combine a precision temperature

controller and a low-noise laser diode driver in one instrument.

The temperature controller delivers bidirectional current to

Peltier Effect thermoelectric coolers (TEC), or unidirectional

current to resistive heaters (RH)[1]. The laser driver operates in

either constant current or constant power mode, maintaining

very stable current to the laser.

The fundamental operating principle of the temperature

controller is that the controller adjusts the output drive current

in order to change the temperature of the sensor that is

connected to the thermal load. The goal is to make the sensor

temperature match the setpoint temperature, and then keep

them equal in spite of changes to ambient conditions and

variations in thermal load.

The laser driver operates on similar principles, attempting to

match the actual laser (or photodiode) current to the user-

defined setpoint, adjusting as required. While output is

enabled, the controller continuously compares the setpoint

laser current and the actual current. If there is a difference

between the setpoint and actual, the controller adjusts the

output current until the difference is zero.

The controller includes features that help protect the load

from damage, and also make it more versatile in a wide array

of applications.

• Current Limits: The adjustable current limits must be set

correctly in order to avoid over-driving and damaging the

TE/heater and laser.

• Voltage Limit: The voltage to the TEC can be limited

through remote commands and the voltage to the laser

can be limited on screen.

• Temperature Limits: Set high and low temperature limits

to protect the laser. If temperature limits are exceeded,

TE current will be disabled. Optionally, LD current can be

configured to disable as well.

• Temperature Control Loop: The temperature controller

employs a smart Proportional-Integral-Derivative (PID)

control loop to adjust the drive current. The terms are user-

adjustable and, when properly configured, will quickly

settle the load temperature with minimal overshoot and

ringing.

• IntelliTune:

Wavelength’s

proprietary

algorithm

characterizes the TEC/Sensor system’s response to

the LDTC LAB and determines the optimal PID control

coefficients. Then, it automatically adjusts the PID values

as setpoint, tuning mode, or bias current are changed.

• Disconnect/Failure Protection: If a short or open circuit

is detected at the temperature sensor, thermoelectric, or

laser, the respective output current is disabled.

[1]

The LDTC LAB does not support packages where the TEC/RH is

connected to the laser case.

INSTRUMENT OVERVIEW

WHAT’S IN THE BOX

• LDTC LAB: Combination Laser Driver and Temperature

Controller Instrument

• Power Cable, type appropriate for final location

• 15+2 Male D-SUB plug and pins for TC connection

• 15-pin Male D-SUB plug and pins for connection to Type A

laser diodes (passive interlock jumper installed)

• 15-pin Female D-SUB receptacle and pins for connection

to Type C laser diodes (passive interlock jumper installed)

• 50 Ω BNC Terminator for Active Lock BNC

• Two 3.15 A fuses are installed in the red fuse tray in the

power entry module on the back panel

• Keys for the key switch

REQUIRED AND OPTIONAL

EQUIPMENT

FOR SET UP

• Optional test loads with appropriate heatsinking (both

laser and thermoelectric) OR

• Thermoelectric/Resistive Heater with temperature sensor

for feedback, and laser diode

COMPUTER REQUIREMENTS FOR

REMOTE OPERATION ONLY (OPTIONAL)

Operating System: Windows Vista SP2 or later

Note: See

page 13 for Remote Operation

ESD INFORMATION

Before proceeding, it is critical that you take precautions to

prevent electrostatic discharge (ESD) damage to the laser

diode. ESD damage can result from improper handling of

sensitive electronics, and is easily preventable with simple

precautions.

For more information regarding ESD, see Application Note

AN-LDTC06: Basics: Electrostatic Discharge (ESD).

We recommend that you always observe ESD precautions

when operating the LDTC LAB.

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