Analog Technologies Low Noise Constant Current Laser Driver ATLS1A103 FEATURES The controller has 2 types of packages: through hole mount and surface mount. The latter saves PCB space the controller takes. Ultra Low Noise: <10µA* High Current without Heat Sink: 1A High Absolute Accuracy: <0.1% Figure 1 is the actual size top view of the ATLS1A103, which shows the pin names and locations. Its thickness is 5mm. High Stability: 100ppm/°C Dual Modulation Ports: High/Low Speed Complete Shielding Compact Size SMT Package Available SPECIFICATIONS Maximum output current: 1A Output current noise: (0.1Hz to 0.5MHz RMS) <10µA Current set voltage range: 0 to 2.5V Current limit set voltage range: 0 to 0.5V APPLICATIONS Modulation response bandwidth: 350KHz Drive laser diodes with low noise, including DPSSL, EDFA, fiber laser, direct diode lasers, etc. Minimum drop out voltage: 0.3V + 0.5×Iout DESCRIPTION Power supply voltage range: 3.5V to 5.5V The ATLS1A103 is an electronic module designed for driving diode lasers with up to 1A low noise current. The output voltage is 1.5V to 4V when powered by a 5V power supply. It uses two drivers, one is switch mode and the other is linear mode. The former results in high power efficiency, the latter keeps the output noise low and allows high modulation speed. Operating case temperature: −25°C to 85°C *Total RMS between 0.1Hz to 0.5MHz. When the maximum power consumed by the controller is maintained to <1W, it does not require a heat sink to operate. The output current of the ATLS1A103 can be set linearly by an input voltage or modulated by an external signal of up to 350KHz in bandwidth, resulting in 1µS rise and fall time. A high stability low noise 2.5V reference voltage is provided internally for setting the output current. This reference can also be used as the voltage reference for external ADCs (Analog to Digital Converters) and DACs (Digital to Analog Converters). The ATLS1A103 is packaged in a 6 sided metal enclosure, which blocks EMIs (Electro-Magnetic Interferences) to prevent the controller and other electronics from interfering each other. (Iout: output current) OPERATION PRINCIPLE Figure 2 is the block diagram of the controller. The shut down control circuit accept signals from 3 sources: external shut down, over-current and over-temperature signals. When one of these signals is activated, the controller is shut down. Only when all these 3 signals go up, the soft-start circuit starts enabling the low noise driver. The temperature sensor circuit turns down the controller upon detecting the temperature to be 120°C. The current limiter circuit monitors the output current and shuts down the controller upon detecting the output current exceeds the pre-set value. When controller is shut down, the voltage reference is also shut down. SDN 100KΩ 1 1 2 3 4 5 6 12 11 10 9 8 7 VPS PGND LDC LDA 19.4 TMPO LPGD GND 2 3 LILM 4 LIS 14.5 Figure 1 Pin Names and Locations VPS 10pF LISL SDN GND 2P5V LILM LIS LIO 12 Voltage reference Current limiter 5 LIO 6 Shutdown & softstart circuit 11 10 PGND LDC Laser Diode Temp. sensor LDA Current sensor & low noise driver 9 8 7 TMPO LPGD Figure 2 Block Diagram 5 50 E. Weddell Drive, Suit e 4, Sunnyvale, CA 94 08 9, U. S. A. Tel.: (4 08 ) 7 47 -9 76 0, Fax: (40 8) 74 7-97 70 , W eb: w w w .analogt echnologies.com © Copyrights 2000 – 2006, Analog Technologies, Inc. All Rights Reserved. Updated on 1/23/2006 1 Analog Technologies Low Noise Constant Current Laser Driver ATLS1A103 APPLICATIONS Figure 3 shows a typical application circuit. W1 and W2 set the output current limit and output current respectively. Resistor R1 and capacitor C1 form a low pass filters, to lower the noise from the voltage reference. Laser diode D1 is connected between LDA and PGND. It is worth mentioning that the power supply return terminal should be connected to the pin 11 PGND and the cathode of the laser diode should be connected to the pin 12 PGND. These 2 nodes should not be connected together externally and they are connected together internally already by the controller. ATLS1A103 Shut Down 1 S1 SPST W1 20K 1 1 2 3 3 Current limit set Current set (Clock-wise) (Clock-wise) R1 2 2 1M 1 C1 W2 1uF to 10uF 20K 1 2 2 3 4 5 6 SDN VPS GND PGND 2P5V PGND LILM LDA LIS LIO TMPO LPGD 12 11 Power Supply 5V power supply 0V 10 9 down resistor will not be able to pull the pin low enough when the controller loop is not good. When choosing not to use an LED for indicating the working status, leave the LPGD pin unconnected. The LPGD pin can also be connected to a digital input pin of a micro-controller, when software/firmware is utilized in the system. Setting the Output Current The output current limit is set by adjusting W1, which sets input voltages of LILM, pin 4. The output current will be: I_output = 1.1×LILM(V)/2.5V (A). LILM should never be left float. Otherwise, the output current limit may be set to too high a value that the laser might be damaged. The output current is set by adjusting W2, which sets input voltages of LIS, pin 5. The output current will be: D1 Laser Diode 8 7 To ADC Loop Good Indication D2 LED To ADC Figure 3 A Typical Stand-alone Application Schematic Turning the Controller On and Off The controller can be turned on and off by setting the SDN pin high and lower respectively. It is recommended to turn the controller on by this sequence: To turn on: turn on the power by providing the power supply voltage to the controller, turn on the controller by releasing the SDN pin. To turn off: turn off the controller by lowering the voltage of SDN pin, turn off the power by stopping the voltage supply on the VPS pin. When not controlling by the SDN pin: leave it unconnected and turn on and off the controller by the power supply. In Figure 3, S1 is the shut down switch. The internal equivalent input circuit of SDN pin is a pull-up resistor of 100K being connected to VPS in parallel with a 10pF capacitor to the ground. The switch S1 can also be an electronic switch, such as an I/O pin of a micro-controller, with an either open drain or push/pull output. If not using a switch (S1) to control the laser, leave the SDN pin unconnected. D2 is an LED, indicating when the control loop works properly, that is: the output current equals to the input set value. This pin has an internal pull up resistor of 5K to the power supply pin, VPS, pin 10. The pull down resistance is 200Ω. This 5K resistor can drive a high efficiency LED directly. When higher pull up current is needed for driving such as a higher current LED, an external resistor can be placed between the VPS and the LPGD pins. Make sure that the resistor is not too small that the pull I_output = LIS(V)/2.5V (A). When no modulation is needed, it is suggested to use an RC low-pass-filter, the R1 and C1 in Figure 3, to lower the AC noise from the voltage reference source. The time constant of this filter can be between a few to 10’s of seconds. The bigger the time cost, the lower the output noise, but the longer time will be needed to wait the output current to go up. Both of LILM and LIS, only LIS, can be configured by using a DAC, to replace the W1 and W2 in Figure 3. Make sure that the DAC has output low noise, or, if no modulation is needed, an RC low pass filtered by be inserted between the DAC and the LIS pin, similar as shown in Figure 3. The LIS allows modulating the output current by a signal of up to 350KHz in bandwidth. That is, when using a sinewave signal to modulate the LIS pin, the output current response curve will be attenuated by 3dB, or 0.71 times the full response magnitude in current. When using an ideal square-wave to modulate the output current at the LIS pin, the rise and fall time of the output current will be about 1µS. When the modulation signal is a square-wave and low output noise is require, the low-pass-filter can still be used for lowering the output noise. Figure 4 shows such a circuit. The resistor R1 can be between 10K to 1M, depending on the error voltage caused by the switch leakage current. The LILM pin can be set by a POT as shown in Figure 3 or connect to 2P5V. It is recommended not to set the LIS pin to 0V, but keep it >0.05V at all the time. The reason is that the laser diode usually has a junction voltage of 2.5V, when setting the LIS pin voltage to 0V, the output voltage will warble between 0V and 2.5V, cause some oscillation slightly. The LIO can still be used to monitor the output current when the LIS is modulated. The bandwidth of the LIO signal is >10MHz, more than enough for monitoring output current modulated by the LIS signal. 5 50 E. Weddell Drive, Suit e 4, Sunnyvale, CA 94 08 9, U. S. A. Tel.: (4 08 ) 7 47 -9 76 0, Fax: (40 8) 74 7-97 70 , W eb: w w w .analogt echnologies.com © Copyrights 2000 – 2006, Analog Technologies, Inc. All Rights Reserved. Updated on 1/23/2006 2 Analog Technologies Low Noise Constant Current Laser Driver ATLS1A103 1 2 2 R1 2 1 100K C1 10uF W1 10K 2 1 1 3 3 4 5 SDN GND VPS PGND 2P5V PGND LILM LDA LIS 6 LIO S1 SPDT TMPO LPGD 12 11 Power Supply 5V power supply 0V 10 D1 9 8 Laser Diode 7 Digital Modulation Signal Input Figure 4 Low Noise Digital Modulation Circuit Monitoring the Output Current The output current of the controller can be monitored by measuring the voltage on the LIO pin. This feature is very useful for miro-controller based system where the ADC is available and monitoring the current in real time is required. This pin provides a very low noise voltage signal which is proportional to the output current: LIO (V) = I_out*2.5 (V). For example, when the output signal equals to 2.5V, the output current is 1A. The output impedance of this pin is 10Ω and it can be used to drive an ADC directly. It can also be measured by a multimeter during debugging process. Monitoring the Controller Internal Temperature The controller internal temperature can be monitored by measure the voltage at the TMPO pin. The equation is: T = − 1525.04 + 1000 × 2.4182 + 0.28744 × (1.8015 − TMPO) (°C), ATLS1A103 When the P_controller exceeds 1W, a heat sink might be needed. Under this situation, if prefer not to use the heat sink, this is an option: lowering the controller power consumption by reducing the power supply voltage VPS. Please make sure: VPS ≥ V_laser_diode_max + 1V, where V_laser_diode_max is the maximum possible laser diode voltage. First Time Power Up Laser is a high value and vulnerable device. Faults in connections and damages done to the controller during soldering process may damage the laser permanently. To protect the laser, it is highly recommend to use 3 to 4 regular diodes of >1A to form a “dummy laser” and insert it in the place of the real laser diode, when powering up the controller for the first time. Use an oscilloscope to monitor the LDA voltage at times of power-up and power-down, make sure that there is not over-shoot in voltage. At the same time, use an ammeter in serious with the dummy laser, to make sure that the output current is correct. After thorough checking free of faults, disconnect the dummy laser and connect the real laser in place. The controller output voltage range for the laser is between 0.5 to 4V when powered by a 5V power supply. MECHANICAL DIMENSIONS AND MOUNTING The ATLS1A103 comes in 2 packages: through hole mount and surface mount. The former is often called DIP (Dual Inline package) or D (short for DIP) package and has a part number: ATLS1A103−D, and the latter is often called SMT (Surface Mount Technology) or SMD (Surface Mount Device) package and has a part number: ATLS1A103−S. R1.5×4 1 2 3 4 5 6 where TMPO is the voltage at the TMPO pin. Here are some temperature values at typical voltages: T = 102 °C @ TMPO = 1V, T = 12 °C @ TMPO = 2V, 12 11 10 9 8 7 19.4 2 14.5 R1.5×2 T = − 85 °C @ TMPO = 3V. R1.5×2 Controller Power Consumption The power consumption of the controller can be calculated by: P_controller = I_output*(VPS – V_laser_diode), 5.0 4.0 Pin size: 0.5×0.5 12 Top View Side View End View Figure 5 Dimensions of the DIP Package Controller where I_output is the output current; VPS is the power supply voltage; V_laser_diode is the voltage across the laser diode. 5 50 E. Weddell Drive, Suit e 4, Sunnyvale, CA 94 08 9, U. S. A. Tel.: (4 08 ) 7 47 -9 76 0, Fax: (40 8) 74 7-97 70 , W eb: w w w .analogt echnologies.com © Copyrights 2000 – 2006, Analog Technologies, Inc. All Rights Reserved. Updated on 1/23/2006 3 Analog Technologies R1.5 × 4 Orientation Mark Low Noise Constant Current Laser Driver ATLS1A103 5.0 R1.5×4 Outline 12 11 10 9 8 7 1 2 3 4 5 6 PCB Copper without solder pad PCB Hole 19.4 14.5 19.4 2 1.15 2 × 14 R1.5×2 R1.5×2 5.6 0.8 × 2 1.0 × 12 Pin size: 0.5×0.5 11.5 16.8 Top View Side View End View 1.5 × 14 Figure 8 Dimensions of the SMT Package Controller 12 Figure 6 shows the foot print which is seen from the top side of the PCB, therefore, it is a “see through” view. 14.5 Figure 6 Top Side PCB Foot-print for the DIP Package PCB Copper with solder pad 1.5 × 14 3.0 × 14 Figure 7 Top View of the Bottom Side PCB Foot-print “Tent” (i.e. cover the entire via by the solder mask layer) all the vias under the controller, otherwise, the vias can be shorted by the bottom plate of the controller which is internally connected the ground. Please notice that, in the recommended foot print for the DIP package, the holes for pin 2 to 6, and 8 to 12 have larger holes than needed for the pins. This arrangement will make it easier for removing the controller from the PCB, in case there is a rework needed. The two smaller holes, for pin 1 and 7, will hold the controller in the right position. It is also recommended to use large copper fills for VPS, PGND, and the LDC pins, and other pins if possible, to decrease the thermal resistance between the module and the supporting PCB, to lower the module temperature. Please be notice that the SMT version cannot be soldered by reflow oven. It must be soldered manually. 5 50 E. Weddell Drive, Suit e 4, Sunnyvale, CA 94 08 9, U. S. A. Tel.: (4 08 ) 7 47 -9 76 0, Fax: (40 8) 74 7-97 70 , W eb: w w w .analogt echnologies.com © Copyrights 2000 – 2006, Analog Technologies, Inc. All Rights Reserved. Updated on 1/23/2006 4 Analog Technologies Low Noise Constant Current Laser Driver ATLS1A103 ORDERING INFORMATION Part # Description ATLS1A103−D Controller in DIP package ATLS1A103−S* Controller in SMT package* * This surface mount package cannot be soldered by reflow oven. It must be soldered manually with the iron temperature < 610°F (≈321°C). PRICES Quantity ATLS1A103−D ATLS1A103−S 1−9 10 − 49 50 − 199 200 − 999 ≥1000 $95 $85 $75 $65 $55 NOTICE 1. ATI warrants performance of its products for one year to the specifications applicable at the time of sale, except for those being damaged by excessive abuse. Products found not meeting the specifications within one year from the date of sale can be exchanged free of charge. 2. ATI reserves the right to make changes to its products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. 3. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgment, including those pertaining to warranty, patent infringement, and limitation of liability. Testing and other quality control techniques are utilized to the extent ATI deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed, except those mandated by government requirements. 4. Customers are responsible for their applications using ATI components. In order to minimize risks associated with the customers’ applications, adequate design and operating safeguards must be provided by the customers to minimize inherent or procedural hazards. ATI assumes no liability for applications assistance or customer product design. 5. ATI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of ATI covering or relating to any combination, machine, or process in which such products or services might be or are used. ATI’s publication of information regarding any third party’s products or services does not constitute ATI’s approval, warranty or endorsement thereof. 6. IP (Intellectual Property) Ownership: ATI retains the ownership of full rights for special technologies and/or techniques embedded in its products, the designs for mechanics, optics, plus all modifications, improvements, and inventions made by ATI for its products and/or projects. 5 50 E. Weddell Drive, Suit e 4, Sunnyvale, CA 94 08 9, U. S. A. Tel.: (4 08 ) 7 47 -9 76 0, Fax: (40 8) 74 7-97 70 , W eb: w w w .analogt echnologies.com © Copyrights 2000 – 2006, Analog Technologies, Inc. All Rights Reserved. Updated on 1/23/2006 5