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FEATURES Ultra Low Noise: <6A* High Output Current: 1A High Absolute Accuracy: <0.1% High Stability: 100ppm/C Dual Modulation Ports: High/Low Speed Complete Shielding Compact Size SMT Package Available
*Total RMS between 0.1Hz to 2MHz.
Low Noise Constant Current Laser Driver ATLS1A101
Figure 1 is the actual size top view of the ATLS1A101, which shows the pin names and locations. APPLICATIONS Figure 2 shows a stand-alone application circuit, where W1 sets the current limit and the output current at the same time. It is recommended that the current limit is set to 1.1 times of the output current. 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. If choose not to use a switch (S1) to control the laser, leave the SDN pin unconnected. D1 is the laser diode, which is float from the ground and the VPS, with its anode connected to the LDA, pin 9, and cathode connected to the LDC, pin 10. D2 is an LED, indicating when the control loop works properly, that is: the output current equals to the input set value. If choose not to use an LED for indicating the working status, leave the LPGD pin unconnected. Adjusting W1, set input voltages of LILM, pin 3, and LISL, pin 4, and the current limit and the output current will respectively be: I_limit = 1.1*LILM(V)/2.5V (A), I_output = LISL(V)/2.5V (A). LILM and LISL should never be left float. Otherwise, the output current will go too high a value and the laser might be damaged. In addition to using the LPGD pin for monitoring the working status of the controller, the output current can be monitored directly by measuring the voltage of LDC pin. The equation is: I_out = LDC(V)/0.5V (A). For example, when seeing LDC = 0.25V, the output current is 0.25V/0.5V = 0.5A. Figure 3 shows an application where ATLS1A101 is interfaced with a micro-controller. In this circuit, the input current can be set by a DAC (Digital to Analog Converter), the current limit can either be set by a POT (Potentiometer), a pair of resistors, or the same DAC. The output current can now be monitored by an ADC (Analog to Digital Converter). By sensing the logic level of LPGD, pin 8, the working status of the controller can be monitored by a micro-controller (MC), when it is 1, the loop is good; 0, the loop is at fault, which includes open circuit at the laser diode connections, or short circuit at the LDC pin to ground. Shut down pin can also be controlled by the microcontroller, setting it to 1 turns on the controller, 0 off. Please notice that this pin comes with an internal pull up resistor of 100K, it can be ORed by multiple digital ports of several micro-controllers, with each of the port having an open-drain output. The internal voltage reference output, 2P5V, pin 2, can be used as the reference voltage for the ADCs and the DACs. Figure 4 shows the equivalent input circuits of different pins.
APPLICATIONS Drive laser diodes with low noise, including DPSSL, EDFA, fiber laser, direct diode lasers, etc. DESCRIPTION The ATLS1A101 is an electronic module designed for driving diode lasers with low noise current of up to 1A. The ATLS1A101 can be modulated by an external signal. There are two modulation ports for the input signal, one for high speed modulation and the other for low speed. The controller can drive a 1A laser diode of 2V to 3V without using a heat sink. When driving a 1A laser diode of <2V, additional heat sinking is needed. The output current can be set linearly by an input voltage and monitored linearly by an output voltage at the same time. A high stability low noise 2.5V reference voltage is provided internally for setting the output current. This reference can also be as the voltage reference for external ADCs (Analog to Digital Converters) and DACs (Digital to Analog Converters). The ATLS1A101 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. The controller has 2 types of packages: through hole mount and surface mount. The latter saves PCB space the controller takes.
AGND 2P5V LILM LISL P5V LISH
1 2 3 4 5 6 12 11 10 9 8 7 14.5
VPS PGND LDC LDA 19.4 LPGD SDN
Figure 1 Pin Names and Locations
Understanding the internal equivalent circuits well helps designing external circuitries.
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
(c) Copyrights 2000 - 2005, Analog Technologies, Inc. All Rights Reserved.
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Analog Technologies
1 2 (Clock-wise) 3 2 W1 100K 1 3 4 5 6
Low Noise Constant Current Laser Driver ATLS1A101
ATLS1A101 VPS U1 PGND LDC LDA LPGD SDN 12 11 10 D1 9 8 Laser Diode Power Supply 5V power supply 0V Voltmeter
AGND 2P5VR LILM LISL P5V LISH
7 Shut Down S1 SPST Loop Good Indication D2 Green LED (Optional)
(Optional)
Figure 2 A Typical Stand-alone Application Schematic
ATLS1A101 1 2 3 DAC 4 5 6 AGND U1 2P5VR LILM LISL P5V LISH PGND LDC LDA LPGD SDN VPS 12 11 10 D1 9 8 Laser Diode 7 MC MC Power Supply 5V power supply 0V ADC
Figure 3 A Typical Micro-processor-based Application Schematic
ATLS1A101 AGND 2P5V LILM LISL P5V LISH 1 2 3 4 5 6 0.3 (AC) Infinite 1.5M 200K <60 Infinite 49.9K 0.5 Infinite (AC) 2K 12 11 10 9 8 7 VPS PGND LDC LDA LPGD SDN
Figure 4 Equivalent Internal Circuits
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
(c) Copyrights 2000 - 2005, Analog Technologies, Inc. All Rights Reserved.
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Analog Technologies
W1 1 100K 3 2
Low Noise Constant Current Laser Driver ATLS1A101
ATLS1A101 1 2 3 AGND U1 2P5VR LILM LISL P5V LISH PGND LDC LDA LPGD SDN VPS 12 11 10 D1 9 8 Laser Diode 7 Power Supply 5V power supply 0V
(Clock-wise) 4 5 6 S1 SPDT
Digital Modulation Signal Input
Figure 5 Low Noise Digital Modulation Circuit SPECIFICATIONS Maximum output current: Output current noise: (0.1Hz to 2MHz RMS) Low speed current set voltage: High speed current set voltage: 1A <6A 0 to 2.5V 0 to 0.5V directly from a micro-controller. Please notice that when using a PWM signal for setting the current limit voltage LILM, a low pass filter, an RC network, will be needed; for the LISL pin, this filter is not needed, since there is an internal low pass filter. It is recommended not to set the LISL 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 LISL pin voltage to 0V, the output voltage will warble between 0V and 2.5V, cause some oscillation slightly. When high speed current modulation is needed, feed the modulation signal to LISH (no need to connect LISH to P5V pin). As LISH change from 0 to 0.5V, the output current changes from 0 to 1A linearly. The fall and rise time is about 1S, and the full power bandwidth is about 300KHz. Using LISH pin as the modulation signal input port results in high speed modulation, however, the noise from the modulation signal source will be converted into output current noise. Figure 5 shows a low noise digital modulation circuit. The switch can be any analog switch, but having low leakage current. W1 sets the output current limit and the peak value of the modulated output current. Make sure that the current limit is set to approximately 1.1 times the peak value of the modulated output current. MONITORING THE OUTPUT CURRENT The output current can be monitored in real time by measuring the voltage on the LDC pin. The formula is: I_output = LDC(V)/0.5V (A). For example, when seeing the LDC pin has a voltage of 0.5V, the output current = 0.5V/0.5V = 1A. Use a high input impedance voltage meter or DAC to
Low speed modulation frequency: 0.1Hz High speed modulation frequency: 300KHz Power supply voltage range: Power supply input current: Operating temperature: CURRENT LIMIT FUNCTION This is how the current limit pin works: there is an internal current sense circuit. Its output is sent to compare with the current limit set-point voltage. Upon detecting the output current being higher than the set limit, the controller turns off the output, wait for a few 10's of mS, and turns the controller back on. Therefore, the current limit function can only be used for protection purpose, not for regulating the output current. MODULATING OUTPUT CURRENT When low speed current modulation is needed, connect LISL pin to the modulation signal. As LISL changes from 0 to 2.5V, the output current changes from 0 to 1A linearly. The rise and fall time achieved by modulating LISL is about 4 seconds and the equivalent bandwidth is about 0.1Hz. The advantage of using LISL as the modulation signal input port is that the output current noise will not increase. The disadvantage is that the speed is not high. The LISL pin can be set by a POT, DAC, or a PWM signal 4.8V to 5.5V output current + 10mA -25C to 85C
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
(c) Copyrights 2000 - 2005, Analog Technologies, Inc. All Rights Reserved.
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Analog Technologies
Low Noise Constant Current Laser Driver ATLS1A101
2. If choose not to control the SDN pin for turning on the laser, leave the SDN pin unconnected. There is an internal capacitor holding SDN pin to logic low. Now, the laser can be turned on and off by using the VPS pin. 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 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 3V.
monitor the output current, such as >5K. Otherwise, some error will be introduced at the output current. When the impedance is 5K, the current error caused at the output is about 0.01%. Please be aware that adding capacitor on this pin will increase the high frequency noise current. Therefore, when monitoring the output current on this pin continuously, insert a resistor of about >5K in series with the voltage meter or ADC. In this way, there is no big capacitance added on the LDC pin. Under no-fault operation conditions, the output voltage of LDC is always the same as that of LISH. POWER UP PROCEDURE Laser diode is a vulnerable device. Special cautions must be taken for turning on the controller. These are the recommendations: 1. Hold the SDN pin to ground by a mechanical switch or an electronic logic device when turning on the power on the VPS pin and release the SDN pin to logic high after the VPS voltage is stabilized to turn on the laser.
PIN DESCRIPTIONS Pin # 1 2 Pin Name AGND 2P5V Pin Type Ground Analog output Analog input Function Analog signal ground. Connect the grounds of the potentiometer W1, ADCs and/or DACs. Reference voltage of 2.5V. It can source or sink 3mA current. This pin sets the output current limit. This pin is used for setting the maximum laser current limit and protecting the laser, but not for regulating the output current. When connecting this pin to the 2P5V, the current limit is set to 1.1A. This pin set the output current linearly by an analog input voltage at low speed. When setting this pin to 2.5V, the output current is 1A. Keep this voltage >0.05V if possible. It is recommended not to set this pin's voltage to 0V because the output voltage may oscillate due to the junction voltage of the laser diode. This pin is a filtered and divided (by 5) output voltage of LISL. When LISL has a voltage of 2.5V, the P5VL voltage is 2.5V/5 = 0.5V. The output impedance of this pin is about 200K. This pin sets the output current directly. When its voltage is 0.5V, the output current is 1A. Shut down control, negative logic, 0 = shut down; 1 = turn on. SND >1.4V = enable, <0.95V = shut down, nominal threshold voltage = 1.2V. The input current is between 3A and 8A. Control loop good indication. When this pin is high, >2V, the Never leave this pin unconnected. It is highly recommended to use this pin for turning on the laser after the power supply is up and turning off the laser before the power supply is shut down. This pin can be used to drive Note Do not connect the power supply ground to here.
3
LILM
4
LISL
Analog input
Never leave unconnected.
this
pin
5
P5VL
Analog output Analog input
6
LISH
7
SDN
Digital input
8
LPGD
Digital
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
(c) Copyrights 2000 - 2005, Analog Technologies, Inc. All Rights Reserved.
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Analog Technologies
output 9 10 11 12 LDA LDC PGND VPS Power output Analog output Power ground Power input
Low Noise Constant Current Laser Driver ATLS1A101
an LED directly, without using any additional components.
control loop is working properly. When this pin is low, <0.3V, the laser diode is bad, or there is a short or open circuit at the laser diode connection. This pin drives the anode of the laser diode. This pin drives the cathode of the laser diode. It has the same voltage potential as the LISH pin. Connect this pin directly to power supply return node (0V). Power supply input. The driver works under VPS = 4.8V to 5.5V.
Never short this pin to any other pins, otherwise, the laser may be damaged.
MECHANICAL DIMENSIONS AND MOUNTING The ATLS1A101 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: ATLS1A101-D, and the latter is often called SMT (Surface Mount Technology) or SMD (Surface Mount Device) package and has a part number: ATLS1A101-S.
R1.5x4 1 2 3 4 5 6 12 11 10 9 8 7
Figure 7 Top Side PCB Foot-print for the DIP Package
PCB Copper with solder pad
1.5 x 14
19.4 2
3.0 x 14
Figure 7 Top View of the Bottom Side PCB Foot-print
14.5 R1.5x2
R1.5x4 1 2 3 4 5 6 14.5 14 13 12 11 10 9 5.0
R1.5x2 Pin size: 0.5x0.5 12 5.0 4.0 Top View Side View End View
19.4 2
Figure 6 Dimensions of the DIP Package Controller
R1.5 x 4 Orientation Mark
1.15
R1.5x2
Outline
R1.5x2 5.6 Top View Side View End View Pin size: 0.5x0.5 11.5 16.8
PCB Copper without solder pad PCB Hole 19.4 2 x 14
Figure 8 Dimensions of the SMT Package Controller Figure 7 shows the foot print which is seen from the top side of the PCB, therefore, it is a "see through" view. 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.
1.0 x 12
0.8 x 2 1.5 x 14 12
14.5
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
(c) Copyrights 2000 - 2005, Analog Technologies, Inc. All Rights Reserved.
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Analog Technologies
ORDERING INFORMATION Part # ATLS1A101-D ATLS1A101-S*
Low Noise Constant Current Laser Driver ATLS1A101
Description Controller in DIP package Controller in SMT package*
* This surface mount package cannot be soldered by reflow oven. It must be soldered manually with the iron temperature < 610F (321C). PRICES Quantity ATLS1A101-D ATLS1A101-S 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. 1-9 10 - 49 50 - 199 200 - 999 1000
$95 $95
$85 $85
$75 $75
$65 $65
$55 $55
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
(c) Copyrights 2000 - 2005, Analog Technologies, Inc. All Rights Reserved.
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