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LD2000R
OEM Laser Diode Driver
with Analog Modulation

User Guide

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Summary of Contents for LD2000R

Page 1: ...LD2000R OEM Laser Diode Driver with Analog Modulation User Guide ...

Page 2: ...ent Circuit 4 4 3 Constant Power Feedback Loop 4 4 4 Theory of Operation 6 Chapter 5 Operating the LD2000R 8 5 1 Setup 8 5 2 Setting the Feedback Resistor 10 5 3 Operating Modes 11 5 3 1 CW Operation 11 5 3 2 Analog Modulation 11 5 3 3 External Modulation Operation 12 Chapter 6 Specifications 14 Chapter 7 Mechanical Drawing 15 Chapter 8 Regulatory 16 Chapter 9 Thorlabs Worldwide Contacts 17 ...

Page 3: ...Description Direct Current Alternating Current Both Direct and Alternating Current Earth Ground Terminal Protective Conductor Terminal Frame or Chassis Terminal Equipotentiality On Supply Off Supply In Position of a Bi Stable Push Control Out Position of a Bi Stable Push Control Caution Risk of Electric Shock Caution Hot Surface Caution Risk of Danger Warning Laser Radiation Caution Spinning Blade...

Page 4: ...operation and technical data in this instruction manual will only apply when the unit is operated correctly SHOCK WARNING Warning is given when there is danger of injury to users CAUTION Caution is given when there is a possibility of damage to the product WARNING Given when there is danger of injury to users ...

Page 5: ...h functions can also be controlled via an external voltage source The LD2000R supports a wide range of laser diodes with drive currents up to 100 mA and photodiode currents from 20 µA to 2 mA The LD2000R also has an external modulation input to support applications that require modulating the laser output Figure 1 Compatible LD Pin Codes NOTE The Laser Diode case must remain floating with respect ...

Page 6: ...LOW_START pin 4 2 Limit Current Circuit The limit current circuit is a constant current source which can be set by the on board trim pot or an external control voltage This determines the maximum drive current that can be supplied to the laser The transfer function for this control is 40 mA V The current limit also determines the laser current when operating in the constant current mode 4 3 Consta...

Page 7: ...SETPOINT voltage and the Analog Modulation Voltage as follows 𝑉𝑆𝑒𝑡𝑝𝑜𝑖𝑛𝑡 𝑉𝑃𝐷 𝐶𝑢𝑟𝑟𝑒𝑛𝑡 𝑆𝑒𝑡𝑝𝑜𝑖𝑛𝑡 𝑉𝐴𝑛𝑎𝑙𝑜𝑔 The control loop integrator has a time constant of approximately 16 5 µs set by a 0 033 µF integrating capacitor The loop time constant can be extended by adding an external capacitor across CX1 and CX2 Note all control signals are based on the photodiode current The user must refer to the manufact...

Page 8: ...gram The laser power is regulated through an integrating feedback loop The setpoint of the feedback is determined by the PWR LIMIT control trimpot and the OUTPUT ADJUST knob in external modulation mode the external voltage is used in place of the OUTPUT ADJUST An internal transimpedance amplifier converts the laser feedback current to a voltage that is used as the error signal for the feedback loo...

Page 9: ... monitor photocurrent The total transimpedance gain should be set so that the photocurrent at the maximum laser power equals 2 5 V Since VError has a maximum value of 2 5 V we can derive the value of an external feedback resistor needed to set the transimpedance for any laser 𝑅𝐹 2 5 V 𝐼𝑀𝑜𝑛 where RF is the transimpedance gain needed and IMon is the monitor photocurrent for your laser 𝑅𝐹 𝑅𝐹 𝐸𝑋𝑇 20 𝑘...

Page 10: ... a complete laser diode driver system We recommend using printed circuit board construction to achieve optimum results The pinouts for the LD2000R are provided in Figure 1 and described below The LD2000R can be used with A D or F style diodes The D and F style diodes will need to be configured like an A style diode see page 3 for diagrams Please note that the EK2000 is not compatible with the F Pi...

Page 11: ...n board trimpot 6 PD Current Setpoint This pin controls the PD Current according to a transfer function of 50 µA V with 0 V being the laser is completely off 0 PD current The laser output increases as this voltage increases 7 REF Out This is a buffered 2 5V voltage reference 8 PD AMP Out This is an analog voltage proportional to the photodiode current and referenced to one half the supply voltage ...

Page 12: ...ne by following the procedure below 1 Determine the appropriate feedback gain using the following calculation 𝑅𝐹 𝐸𝑋𝑇 20 000 8 000𝐼𝑀𝑂 1 where RF EXT is the external gain setting resistor to be added in ohms and IMON is the monitor current for a particular laser in Amps 2 Pick the nearest standard value resistor 0 25 W 5 or better 3 Connect RF EXT across pins 8 and 12 of the LD2000R SHOCK WARNING Th...

Page 13: ...odulation to FULL ON 6 Short pin 16 to ground 7 Turn both the PD Current Trimpot and the Current Limit Trimpot counterclockwise 20 turns each to set these at their minimum operating points 8 Turn the DC power supply on and use a voltmeter to monitor the LIMIT OUT on pin 18 9 Adjust the Current Limit Trimpot clockwise slowly while observing the LIMIT OUT to set the maximum operating current for you...

Page 14: ...t IMON use the following equation 𝑅𝐹 𝐸𝑋𝑇 50 000 20 000𝐼𝑀𝑂 2 5 5 3 3 External Modulation Operation The laser output power can be controlled via an external modulation voltage while operating in the Constant Power Mode The laser output is inversely proportional to the modulating voltage with 0 V being the laser fully on and 2 5 V turning the laser fully off 1 To use the external modulation perform t...

Page 15: ...here below 2 5V since the default feedback gain is usually too high for most lasers 3 If the feedback gain is too low for a laser i e the maximum laser power can be reached at a point somewhere below the maximum setting of PWR Limit than use care to set the PWR Limit control to the maximum desired operating power before applying the modulating voltage The turn off voltage is dependent on matching ...

Page 16: ...nalog Voltage Photodiode Current Range 20 to 125 A Factory Configured1 Long Term Drift 24 hrs 0 1 Temperature Coefficient 100 ppm C Analog Bandwidth 3 db Bandwidth Nominal 10 kHz2 Power Supply Supply Voltage V 8 to 12 VDC Supply Current 30 mA Plus Laser Current General Dimensions 2 x 1 3 x 0 5 Operating Temperature 0 to 40 C Storage Temperature 0 to 70 C Packaging PCB DIP Plastic Encapsulated 1 Hi...

Page 17: ...OEM Laser Diode Driver Chapter 7 Mechanical Drawing Rev I May 21 2018 Page 15 Chapter 7 Mechanical Drawing Figure 4 LD2000R Mechanical Drawing ...

Page 18: ...labs products such as Pure OEM products that means assemblies to be built into a unit by the user e g OEM laser driver cards Components Mechanics and optics Left over parts of units disassembled by the user PCB s housings etc If you wish to return a Thorlabs unit for waste recovery please contact Thorlabs or your nearest dealer for further information Waste Treatment is Your Own Responsibility If ...

Page 19: ...pan Thorlabs Japan Inc sales thorlabs jp UK and Ireland Thorlabs Ltd sales uk thorlabs com techsupport uk thorlabs com Scandinavia Thorlabs Sweden AB scandinavia thorlabs com Brazil Thorlabs Vendas de Fotônicos Ltda brasil thorlabs com China Thorlabs China chinasales thorlabs com Chapter Thorlabs Worldwide Contacts For technical support or sales inquiries please visit us at www thorlabs com contac...

Page 20: ...www thorlabs com ...

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