Analog Technologies, Inc. LDA1-CP1 Dual Mode Laser Driver Main features: high power, high precision, high stability, high efficiency, and small package. Applications: DPSS, EDFA, and instrumentations. Part number: Maximum output current: 2A LDA1-CP1 Maximum output voltage on LDA: Laser current and power indication voltage: Laser current indication absolute accuracy: Laser current set-point voltage: Laser power set-point voltage: Current output noise: Power supply input voltage: Operation mode: 0.9×Vps 0 to 2.5V ±0.5% 0 to 2.5V 0 to 2.5V 0.05% (RMS)@2A 3.2V to 5.5V ACC (Automatic Current Control) and APC (Automatic Power Control) 0°C to +85°C 25.4mm × 20 mm × 4.6mm Operating temperature: Module dimension (approximately): Pin Descriptions Figure 2 illustrates the pin assignment on the module and basic application schematics. Pin 1 SDNG, shut down, digital input. Negative logic, >2.3V = enable, <0.5V = shut down, norminal threshold voltage = 1V. Its internal circuit is shown in Figure 2. The diode is for shortening the shut down time. Pin 2 CLPGD, control loop good indication, digital output. A HI level indicates control loop locked. This pin is an open drain output and pulled up by a 20K resistor to VPS. Pin 3 P/CM, power/current mode indication, analog output. HI = power mode, LO = current mode. Low output impedance, capable of driving 20mA load. Pin 4 GND, signal ground pin. Connect ADC and DAC grounds to here. Pin 5 2.5V, reference voltage, analog output. It is used by the internal DACs as the reference voltage. It can source and sink 5mA current with 20ppm/°C stability max. Pin 6 LIS, laser current set-point voltage, analog input. 0V to 2.5V sets the output current from 0 to 2A linearly. The input impedance of this pin is 100KΩ. This pin can be set by an external analog signal source, such as the output of a closed-looped op-amp, POT, or DAC. Pin 7 LIO, laser current output indication, analog output. 0V to 2.5V indicates the laser current of from 0 to 2A linearly. 550 E. Weddell Drive, Suite 4, Sunnyvale, CA 94089, U. S. A. Tel.: (408) 747-9760, Fax: (408) 747-9770, Web: w w w .analogt echnologies.com Copyrights 2000– 2003, Analog Technologies, Inc. All Rights Reserved. 1 Analog Technologies, Inc. LDA1-CP1 Pin 8 LPS, laser power set-point voltage, analog input. 0V to 2.5V sets the laser output power from 0 to the maximum value linearly. The input impedance of this pin is 100KΩ. This pin can be set by an external analog signal source, such as the output of a closed-looped op-amp, POT, or DAC. Pin 9 GND, signal ground pin. Connect ADC and DAC grounds to here. Pin 10 LPO, laser power output voltage, analog output. Low impedance output. The (positive-going) output of a TIA (Trans-Impedance Amplifier) for the photodiode in the laser. The transimpedance is set by an external resister between LPO pin and PDCT (pin 11). Pin 11 PDCT, photodiode cathode, analog input. The TIA’s input. Drawing current out from this pin will bring the LPO pin voltage going up-ward. Pin 12 LDA, laser diode anode, analog output. This pin is used to drive a laser of which the cathode is connected to the case and the case is connected to the ground. See Figure 1. Pin 13 LDC, laser diode cathode, analog output. This pin is internally connected to ground. Connect it directly to the laser’s cathode which is also the case of the laser. See Figure 1. Pin 14 GND, ground. Connect power supply return rail to here. Pin 15 VPS, power supply, analog power input. The driver works from 3.2V to 5.5V. Pin 16 SYNCO, sync output, digital output. This pin can be used to synchronize another switch mode driver such as for TEC or power supply so that the other drivers will not interfere with this laser driver. The switching frequency is set at 700 KHz. There is a 10K resistor before this pin to the switcher output. This pin can also be used to see the switcher’s output voltage. Mode Setting A. Set the driver to constant current mode without over power protection In this mode, the laser is always operating at constant current mode. 1. Set LIS = 2.5V × Ilaser 42.0A, where Ilaser is the set-point laser current. 2. Make sure LPS is greater than LPO, for example by connecting LPS to 2.5V reference and making photodiode transimpedance amp resistor = 0 ohms. B. Set the driver to constant current mode with over power protection In this mode, the laser is operating at the constant current mode unless the laser output power reaches the preset maximum power. When the laser output power reaches the protection power, the laser will be operating in constant power mode. 1. Set LIS = 2.5V × Iset 42.0A, where Ilaser is a laser set-point current. 2. Set LPS to the voltage generated at the LPO pin by the internal TIA (Trans-Impedance Amplifier) when the laser is outputting the protection power level. The TIA converts the current of the powersensing PD (Photo Diode) into a voltage, with the gain set by an external resistor connected between the PDCT and LPO pins. Make sure that the set-point laser current is at least 5% less than the current needed to generate the protection laser power level. C. Set the driver to constant power mode without over current protection 550 E. Weddell Drive, Suite 4, Sunnyvale, CA 94089, U. S. A. Tel.: (408) 747-9760, Fax: (408) 747-9770, Web: w w w .analogt echnologies.com Copyrights 2000– 2003, Analog Technologies, Inc. All Rights Reserved. 2 Analog Technologies, Inc. LDA1-CP1 In this mode, the laser is always operating in the constant power mode (up to the maximum rated current of 2.0A). 1. Connect LIS to 2.5V reference pin. 2. Set LPS to the voltage value which is generated at the LPO pin by the internal TIA (TransImpedance Amplifier) when the laser is outputting the set-point power. The TIA converts the current of the power-sensing PD (Photo Diode) into a voltage, with the gain set by an external resistor connected between the PDCT and LPO pins. Make sure that the laser can output the setpoint power by a current of less than 1.90A. D. Set the driver to constant power mode with over current protection In this mode, the laser is operating in the constant power mode unless the laser current reaches a predetermined protection current. When the laser reaches the protection current, the laser will be operating in constant current mode. 1. Set LIS = 2.5V × Iprotect 42.0A, where Iprotect is the predetermined protection current. 2. Set LPS to the voltage value which is generated at the LPO pin by the internal TIA (TransImpedance Amplifier) when the laser is outputting the set-point power. The TIA converts the current of the power-sensing PD (Photo Diode) into a voltage, with the gain set by an external resistor connected between the PDCT and LPO pins. Make sure that the laser can output the setpoint power by a current of less than 95% of the protection current. LDA1-CP1 Pin 1 SDNG 2 R 1 100K 1D 2 Internal chip control input MA785CT-ND C 0.68uF Figure 1 550 E. Weddell Drive, Suite 4, Sunnyvale, CA 94089, U. S. A. Tel.: (408) 747-9760, Fax: (408) 747-9770, Web: w w w .analogt echnologies.com Copyrights 2000– 2003, Analog Technologies, Inc. All Rights Reserved. 3 Analog Technologies, Inc. D1 Green LED R3 1K 2 1 LDA1-CP1 LDA1-CP1 S1 SPST SDNG 2 CLPGD 3 2 R5 1K 1 D3 3 Green LED 5 6 1 W2 10K 3 2 1 P/CM 4 (Clock-wise) To a voltmeter 2 W3 10K 7 8 SYNCO VPS PGND GND PGND 2.5V LDA LIS PDCT LIO LPO LPS GND 16 other synchronizable modules 15 +5V 14 To power supply GND 13 Laser LD/PD 12 LD 11 PD 10 9 To Voltmeter 1 1 D2 Green LED R4 1K 2 1 W1 2 2 R1 10K 1 10K 3 2 R2 499 1 Figure 2A Self-contained LDA1-CP1 To micro-controller To micro-controller To signal GND To ADC & DAC To DAC To ADC To DAC 2 3 4 5 6 7 8 SDNG CLPGD SYNCO VPS P/CM PGND GND PGND 2.5V LDA LIS PDCT LIO LPO LPS GND 16 other synchronizable modules 15 +5V 14 To power supply GND 13 12 LD 11 PD 10 9 To ADC W1 To signal GND Laser LD/PD 1 To micro-controller 1 2 2 R1 10K 1 2 R2 499 1 3 10K Figure 2B Micro-processor Based 550 E. Weddell Drive, Suite 4, Sunnyvale, CA 94089, U. S. A. Tel.: (408) 747-9760, Fax: (408) 747-9770, Web: w w w .analogt echnologies.com Copyrights 2000– 2003, Analog Technologies, Inc. All Rights Reserved. 4 Analog Technologies, Inc. LDA1-CP1 Pin Configurations and Mechanical Dimensions 1 SDNG 2 CLPGD 3 SYNCO 16 16 1 VPS 15 15 2 P/CM PGND 14 14 3 4 GND PGND 13 13 4 5 2.5V LDA 12 12 5 6 LIS PDCT 11 11 6 7 LIO LPO 10 10 7 8 LPS GND 9 9 8 2.54mm 25.4mm 1.26mm 18mm 2.26mm 20mm 1.26mm Figure 4 Bottom View of LDA1-CP1-S Figure 3 Top View of LDA1-CP1-S 4.6mm 4.6mm 3mm 0.6mm 2.54mm 0.42mm 3mm 18mm Figure 5 Side View of LDA1-CP1-D Figure 6 End View of LDA1-CP1-D Note: The Dual Mode Laser Drivers come in two types of packages: surface mount and through hole. The surface mount package has to be soldered manually, not by reflow oven. The through hole package can be mounted in a socket, soldered manually, or by wave soldering machine. Package type is designated by suffixing D (through hole) or S (surface mount) to the part number. 550 E. Weddell Drive, Suite 4, Sunnyvale, CA 94089, U. S. A. Tel.: (408) 747-9760, Fax: (408) 747-9770, Web: w w w .analogt echnologies.com Copyrights 2000– 2003, Analog Technologies, Inc. All Rights Reserved. 5