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8

LDTC2/2 LASER DIODE DRIVER AND TEMPERATURE CONTROLLER

THEORY OF OPERATION

The LDTC2/2 Laser Diode Driver and Temperature 

Controller combines the drive power of the WLD3343 with 

the temperature stability of the WTC3243.

The LDTC2/2E is enclosed with a cover and base, while the 

LDTC2/2O is open frame without cover or base. Accessory 

heatsinking is required for LDTC2/2O. Both have the same 

functionality.

LASER DIODE DRIVER CURRENT SOURCE

It may be useful to remember that you do not directly set 

the laser drive current setpoint; instead, you adjust a voltage 

signal that represents the output current. The setpoint 

voltage is controlled by the onboard trimpot or by an an 

external input.

As current is driven through the load, there is a voltage drop 

across the load because of the impedance. As the current 

increases, the voltage drop may increase to the point that it 

reaches the Compliance Voltage limit of the current source. 

Once that occurs, the current source is no longer able to 

increase the current driven to the load, even if you increase 

the setpoint.

TEMPERATURE CONTROLLER

The WTC3243 delivers bidirectional current to a Peltier Effect 

thermoelectric cooler, or unidirectional current to a resistive 

heater. The controller adjusts the output current in order to 

change the temperature of the sensor that is connected to 

the thermal load. The goal is to make the voltage across the 

sensor match the setpoint voltage, and then keep them equal 

in spite of changes to ambient conditions and variations in 

thermal load.

FEATURES

The LDTC2/2 integrated laser driver and temperature 

controller includes features that help protect your laser and 

make the driver more versatile in a wide array of applications:

•  The current limits (laser, heating, cooling) are set by  

onboard trimpots and protect the laser from over-current 

and over-/under-temperature conditions.

•  Slow-start delays the laser current ramp by 250 msec, 

and then ramps the current to the setpoint.

•  Constant Power operation is available, where the driver 

adjusts the laser forward current in order to maintain a 

constant photodiode current.

•  Available remote LD & TC setpoint control.

•  Separate heating and cooling current limits.

SAFETY INFORMATION 
& THERMAL DESIGN 
CONSIDERATIONS

SAFE OPERATING AREA — DO NOT EXCEED 
INTERNAL POWER DISSIPATION LIMITS

Before attempting to operate the LDTC, it is imperative that 

you  first  determine  that  the  laser  driver  and  temperature 

controller will operate within the Safe Operating Area (SOA). 

Operating the unit outside of the SOA may damage the 

controller or the load, and will void the warranty.

Go to the Wavelength Electronics website for the most 

accurate, up-to-date, and easy to use SOA calculators:

Laser Diode Drivers:

www.teamwavelength.com/support/design-tools/soa-ld-calculator/

Temperature Controllers:

www.teamwavelength.com/support/design-tools/soa-tc-calculator/

SOA charts are included in this datasheet for quick reference 

(

page 18

), but we recommend you use the online tools 

instead.

To  ensure  safe  operation  of  the  LDTC 

controller,  it  is  imperative  that  you  

determine if the unit is going to be operating 

within  the  internal  heat  dissipation  Safe 

Operating Area (SOA).

For more information on Safe Operating Area, see our 

Application Note 

AN-LDTC01: The Principle of the Safe 

Operating Area

.

When you assemble and mount the TEC (or heater), 

heatsink, and temperature sensor, make sure the physical 

connections between the components are solid. We 

recommend using thermal paste or thermal washers at the 

load/TEC and TEC / heatsink interfaces. The thermistor must 

be in firm contact with the load in order to achieve stable and 

reliable temperature control.

PREVENT DAMAGE FROM  
ELECTROSTATIC DISCHARGE

Before proceeding, it is critical that you take precautions to 

prevent electrostatic discharge (ESD) damage to the driver 

and your laser. ESD damage can result from improper 

handling of sensitive electronics, and is easily preventable 

with simple precautions.

For more information regarding ESD, see our Application 

Note 

AN-LDTC06: Electrostatic Discharge Basics

We recommend that you always observe ESD precautions 

when handling the LDTC controller and loads.

!

Содержание LDTC2/2E

Страница 1: ...o system components Adjustable trimpots configure heat and cool current limits The WLD3343 Laser Driver maintains precision laser diode curent Constant Current Mode or stable photodiode current Consta...

Страница 2: ...A Laser Diode Type B Laser Diode Type C Laser Diode Common Cathode Laser Diode Anode Photodiode Cathode Common Isolated Photodiode Short the Laser Diode Anode to Photodiode Cathode Common Anode Laser...

Страница 3: ...t set T SET to 0 85 V NOTE To stay within the Safe Operating Area while using the test load VS must not exceed 5 V RECOMMENDED LASER DRIVER TEST LOAD For the laser diode driver recommended simulated l...

Страница 4: ...ge proportional to the current flowing through the laser diode See Table 2 for the transfer function 9 ACT T MON Actual Temperature Monitor Green Monitor the actual voltage produced by the temperature...

Страница 5: ...s voltage output of Photodiode Monitor Pin 2 Connector J2 to forward current through Photodiode 2 RPD 499 for 2 0 mA range RPD 4 99 k for 200 A range NOTE Available on Rev B and later Actual Temperatu...

Страница 6: ...BIENT 25 C Long Term Stability 24 hours 0 05 TAMBIENT 25 C OUTPUT Peak Current IMAX 1 8 2 0 2 2 A With heat sink and fan Compliance Voltage Laser Diode Load 3 0 V Full Temp Range ILD 2 0A 5V Rise Time...

Страница 7: ...Sensor Compatibility Thermistor RTD IC Sensors Sensor Input Voltage Range 4 GND to VDD 2 0 V Sensor Input Damage Threshold 0 7 VDD 7 V VSET Input Impedance 500 k VSET Damage Threshold 0 7 VDD 7 V BIA...

Страница 8: ...Constant Power operation is available where the driver adjusts the laser forward current in order to maintain a constant photodiode current Available remote LD TC setpoint control Separate heating an...

Страница 9: ...CW WIRE OUTPUT CONNECTION Use Table 4 to determine the connection from the LDTC2 2 to your thermoelectric or resistive heater Table 4 Wiring vs Sensor Load Type SENSOR LOAD TEC PIN J3 6 TEC PIN J3 7...

Страница 10: ...e Operating Calculators available on our website TEMPERATURE SETPOINT Wavelength introduces a special setpoint circuit with the LDTC2 2 An onboard trimpot TSET will adjust the voltage from 0 3 to 2 5...

Страница 11: ...only when power is not applied to VDD Setting for 2 0 mA range Setting for 200 A range CC CP CC CP ExtTset Vset PDset Vset PDset ExtTset Figure 8 Select the photodiode range with the PDset jumper The...

Страница 12: ...use proper operator grounding and anti static procedures MONITOR LASER DIODE OR PHOTODIODE CURRENT Equation 1 provides a transfer function for converting the voltage output of LD I M Laser Diode Curre...

Страница 13: ...ow 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 OR Sum ExtTset with tr...

Страница 14: ...onto the corner posts and press PCB into seated position Install the eight screws in the WLD and WTC 4 Install the cover and cables PROPORTIONAL GAIN INTEGRATOR TIME CONSTANT PI TERMS The LDTC2 2 is...

Страница 15: ...r RSENSE vs Maximum Laser Diode Current ILDMAX MAXIMUM OUTPUT CURRENT ILDMAX CONSTANT POWER RSENSE CONSTANT CURRENT RSENSE 50 mA 25 00 20 00 125 mA 10 00 8 00 250 mA 5 00 4 00 500 mA 2 50 2 00 1 25 Am...

Страница 16: ...CC LDC PDA PDC LDA VDD VDD Ext Vset LIM S2 EG2211 R17 1 00K 1 R7 1 00K R19 1 00K R18 150 R16 10K 2 3 1 4 11 U6A 5 6 7 4 11 U6B 9 10 8 4 11 U6C 13 12 14 4 11 U6D R11 1 00K R10 1 00K R12 1 00K R9 1 00K...

Страница 17: ...T T SET T GND ACT T SET T Common Common TEC TEC Sensor R33 10 0K R32 100K 1 2 3 J1 CON3 VDD PMON IMON Ext Vset Remote Enable PMON IMON Ext Vset Rem En Common PD MON Common NO 6 COM 5 NC 4 IN 1 V 2 GND...

Страница 18: ...nd current IMAX specifications Calculate the voltage drop across the controller VDROP VDD VMAX Mark VDROP on the X axis and extend a line upward Mark IMAX on the Y axis and extend a line to the right...

Страница 19: ...sure the temperature sensor is in good thermal contact with the load Operating outside of the ideal region of the temperature sensor The sensor type and bias current should be selected to maximize se...

Страница 20: ...ge 12 for instructions on setting the laser driver current limit Laser driver is compliance limited Check the laser diode specifications to determine the forward voltage VF Make sure that the LDTC2 2...

Страница 21: ...ACK GREEN BLACK DESCRIPTION LASER DIODE CATHODE PHOTODIODE ANODE PHOTODIODE CATHODE LASER DIODE ANODE LOW CURRENT GROUND TEC CONNECTION TEC CONNECTION SENSOR POSITIVE CONNECTION SENSOR NEGATIVE CONNEC...

Страница 22: ...NSIONS LDTC2 2E WITH ENCLOSURE 2 70 68 6 mm 0 15 3 8 mm 2 40 61 0 mm 4 80 121 9 mm 4 20 106 7 mm 0 15 3 8 mm 4 50 114 3 mm 0 13 3 2 mm 4 PLACES 0 30 7 6 mm 1 14 29 0 mm 500 1 27 875 2 22 125 0 32 3 70...

Страница 23: ...5 3 8 mm 2 20 55 9 mm 0 15 3 8 mm 3 70 94 0 mm 0 062 1 6 mm 0 50 12 6 mm 0 50 12 7 mm 4 00 101 6 mm 2 50 63 5 mm 4 20 106 7 mm 0 250 6 3 mm 0 156 4 0 mm 0 750 2 000 3 700 4 000 0 150 2 200 2 500 0 150...

Страница 24: ...LLER MECHANICAL SPECIFICATIONS DIMENSIONS HEATSINK FOOTPRINT 0 78 19 8 mm 0 945 24 0 mm 0 68 17 2 mm 0 945 24 0 mm 2 40 60 9 mm 0 945 24 0 mm 1 25 31 7 mm 0 156 4 0 mm 4 40 tapped holes in device 0 15...

Страница 25: ...E The information contained in this document is subject to change without notice Wavelength will not be liable for errors contained herein or for incidental or consequential damages in connection with...

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