LM2937-2.5,LM2937-3.3 LM2937-2.5, LM2937-3.3 400mA and 500mA Voltage Regulators Literature Number: SNVS015D LM2937-2.5, LM2937-3.3 400mA and 500mA Voltage Regulators General Description The LM2937-2.5 and LM2937-3.3 are positive voltage regulators capable of supplying up to 500 mA of load current. Both regulators are ideal for converting a common 5V logic supply, or higher input supply voltage, to the lower 2.5V and 3.3V supplies to power VLSI ASIC's and microcontrollers. Special circuitry has been incorporated to minimize the quiescent current to typically only 10 mA with a full 500 mA load current when the input to output voltage differential is greater than 5V. The LM2937 requires an output bypass capacitor for stability. As with most regulators utilizing a PNP pass transistor, the ESR of this capacitor remains a critical design parameter, but the LM2937-2.5 and LM2937-3.3 include special compensation circuitry that relaxes ESR requirements. The LM2937 is stable for all ESR ratings less than 5. This allows the use of low ESR chip capacitors. The regulators are also suited for automotive applications, with built in protection from reverse battery connections, two-battery jumps and up to +60V/-50V load dump transients. Familiar regulator features such as short circuit and thermal shutdown protection are also built in. Features n Fully specified for operation over -40C to +125C n Output current in excess of 500 mA (400mA for SOT-223 package) n Output trimmed for 5% tolerance under all operating conditions n Wide output capacitor ESR range, 0.01 up to 5 n Internal short circuit and thermal overload protection n Reverse battery protection n 60V input transient protection n Mirror image insertion protection Connection Diagrams and Ordering Information TO-220 Plastic Package SOT-223 Plastic Package 10011324 Front View Order Number LM2937ET-2.5, LM2937ET-3.3, See NS Package Number T03B 10011325 Front View Order Number LM2937IMP-2.5, LM2937IMP-3.3, See NS Package Number MA04A TO-263 Surface-Mount Package 10011327 Side View 10011326 Top View Order Number LM2937ES-2.5, LM2937ES-3.3, See NS Package Number TS3B (c) 2005 National Semiconductor Corporation DS100113 www.national.com LM2937-2.5, LM2937-3.3 400mA and 500mA Voltage Regulators August 2005 LM2937-2.5, LM2937-3.3 Connection Diagrams and Ordering Information Temperature Range Output Voltage (Continued) NSC Package 2.5 3.3 Package -40C TA 125C LM2937ES-2.5 LM2937ES-3.3 LM2937ET-2.5 LM2937ET-3.3 T03B TO-220 -40C TA 85C LM2937IMP-2.5 LM2937IMP-3.3 MA04A SOT-223 SOT-223 Package Markings L68B L69B Drawing TS3B TO-263 The small physical size of the SOT-223 package does not allow sufficient space to provide the complete device part number. The actual devices will be labeled with the package markings shown. www.national.com 2 SOT-223 (Vapor Phase, 60 seconds) 215C If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. SOT-223 (Infrared, 15 seconds) Input Voltage Continuous 26V Transient (t 100 ms) 60V Internal Power Dissipation (Note 2) 2 kV Operating Conditions(Note 1) Temperature Range (Note 2) Internally Limited Maximum Junction Temperature LM2937ES, LM2937ET -40C TA 125C LM2937IMP -40C TA 85C 150C Storage Temperature Range -65C to +150C Lead Temperature Soldering TO-220 (10 seconds) 260C TO-263 (10 seconds) 230C 220C ESD Susceptibility (Note 3) Input Voltage Range 4.75V to 26V Electrical Characteristics(Note 4) VIN = VNOM + 5V, IOUTmax = 500 mA for the TO-220 and TO-263 packages, IOUTmax=400mA for the SOT-223 package, COUT = 10 F unless otherwise indicated. Boldface limits apply over the entire operating temperature range, of the indicated device, all other specifications are for TA = TJ = 25C. Output Voltage (VOUT) Parameter Output Voltage 2.5V Conditions Typ 5 mA IOUT IOUTmax 3.3V Limit Typ 2.42 2.5 2.38 Units Limit 3.20 3.3 2.56 2.62 V (Min) 3.14 V(Min) 3.40 V(Max) 3.46 V(Max) 7.5 25 9.9 33 mV(Max) 2.5 25 3.3 33 mV(Max) 2 10 2 10 mA(Max) 10 20 10 20 mA(Max) VIN = 5V, IOUT = IOUTmax 66 100125 66 100125 Output Noise 10 Hz-100 kHz, 75 99 Vrms Voltage IOUT = 5 mA Long Term Stability 1000 Hrs. 10 13.2 mV Line Regulation(Note 5) 4.75V VIN 26V, Load Regulation 5 mA IOUT IOUTmax Quiescent Current 7V VIN 26V, IOUT = 5 mA IOUT = 5 mA VIN = (VOUT + 5V), IOUT = IOUTmax Short-Circuit Current Peak Line Transient tf < 100 ms, RL = 100 mA(Max) 1.0 0.6 1.0 0.6 A(Min) 75 60 75 60 V(Min) 26 V(Min) Voltage Maximum Operational 26 Input Voltage Reverse DC VOUT -0.6V, RL = 100 -30 -15 -30 -15 V(Min) tr < 1 ms, RL = 100 -75 -50 -75 -50 V(Min) Input Voltage Reverse Transient Input Voltage Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device outside of its rated Operating Conditions. Note 2: The maximum allowable power dissipation at any ambient temperature is PMAX = (125 - TA)/JA, where 125 is the maximum junction temperature for operation, TA is the ambient temperature, and JA is the junction-to-ambient thermal resistance. If this dissipation is exceeded, the die temperature will rise above 125C and the electrical specifications do not apply. If the die temperature rises above 150C, the regulator will go into thermal shutdown. The junction-to-ambient thermal resistance JA is 65C/W, for the TO-220 package, 73C/W for the TO-263 package, and 174C/W for the SOT-223 package. When used with a heatsink, JA is the sum of the device junction-to-case thermal resistance JC of 3C/W and the heatsink case-to-ambient thermal resistance. If the TO-263 or SOT-223 packages are used, the thermal resistance can be reduced by increasing the P.C. board copper area thermally connected to the package (see Application Hints for more information on heatsinking). Note 3: ESD rating is based on the human body model, 100 pF discharged through 1.5 k. Note 4: Typicals are at TJ = 25C and represent the most likely parametric norm. 3 www.national.com LM2937-2.5, LM2937-3.3 Absolute Maximum Ratings (Note 1) LM2937-2.5, LM2937-3.3 Electrical Characteristics(Note 4) (Continued) Note 5: The minimum input voltage required for proper biasing of these regulators is 4.75V. Below this level the outputs will fall out of regulation. This effect is not the normal dropout characteristic where the output falls out of regulation due to the PNP pass transistor entering saturation. If a value for worst case effective input to output dropout voltage is required in a specification, the values should be 2.37V maximum for the LM2937-2.5 and 1.6V maximum for the LM2937-3.3. Typical Performance Characteristics Output Voltage vs Temperature (2.5V) Output Voltage vs Temperature (3.3V) 10011302 10011303 Quiescent Current vs Output Current (2.5V) Quiescent Current vs Output Current (3.3V) 10011305 10011304 Quiescent Current vs Input Voltage (2.5V) Quiescent Current vs Input Voltage (3.3V) 10011306 www.national.com 10011307 4 LM2937-2.5, LM2937-3.3 Typical Performance Characteristics (Continued) Line Transient Response Load Transient Response 10011309 10011308 Ripple Rejection Output Impedance 10011310 10011311 Maximum Power Dissipation (TO-220) Maximum Power Dissipation (TO-263) (Note 2) 10011313 10011312 5 www.national.com LM2937-2.5, LM2937-3.3 Typical Performance Characteristics (Continued) Low Voltage Behavior (2.5V) Low Voltage Behavior (3.3) 10011314 10011315 Output at Voltage Extremes Output Capacitor ESR 10011317 10011316 Peak Output Current 10011318 www.national.com 6 LM2937-2.5, LM2937-3.3 Typical Application 10011301 * Required if the regulator is located more than 3 inches from the power supply filter capacitors. ** Required for stability. Cout must be at least 10 F (over the full expected operating temperature range) and located as close as possible to the regulator. The equivalent series resistance, ESR, of this capacitor may be as high as 3. 7 www.national.com LM2937-2.5, LM2937-3.3 The figure below shows the voltages and currents which are present in the circuit, as well as the formula for calculating the power dissipated in the regulator: Application Hints EXTERNAL CAPACITORS The output capacitor is critical to maintaining regulator stability, and must meet the required conditions for both ESR (Equivalent Series Resistance) and minimum amount of capacitance. MINIMUM CAPACITANCE: The minimum output capacitance required to maintain stability is 10 F (this value may be increased without limit). Larger values of output capacitance will give improved transient response. ESR LIMITS: 10011319 The ESR of the output capacitor will cause loop instability if it is too high or too low. The acceptable range of ESR plotted versus load current is shown in the graph below. It is essential that the output capacitor meet these requirements, or oscillations can result. IIN = IL / IG PD = (VIN - VOUT) IL + (VIN) IG FIGURE 2. Power Dissipation Diagram The next parameter which must be calculated is the maximum allowable temperature rise, TR (max). This is calculated by using the formula: TR (max) = TJ(max) - TA (max) where: TJ (max) is the maximum allowable junction temperature, which is 125C for commercial grade parts. TA (max) is the maximum ambient temperature which will be encountered in the application. Output Capacitor ESR Using the calculated values for TR(max) and PD, the maximum allowable value for the junction-to-ambient thermal resistance, (J-A), can now be found: (J-A) = TR (max)/PD 10011317 IMPORTANT: If the maximum allowable value for (J-A) is found to be 53C/W for the TO-220 package, 80C/W for the TO-263 package, or 174C/W for the SOT-223 package, no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements. If the calculated value for (J-A)falls below these limits, a heatsink is required. FIGURE 1. ESR Limits It is important to note that for most capacitors, ESR is specified only at room temperature. However, the designer must ensure that the ESR will stay inside the limits shown over the entire operating temperature range for the design. For aluminum electrolytic capacitors, ESR will increase by about 30X as the temperature is reduced from 25C to -40C. This type of capacitor is not well-suited for low temperature operation. Solid tantalum capacitors have a more stable ESR over temperature, but are more expensive than aluminum electrolytics. A cost-effective approach sometimes used is to parallel an aluminum electrolytic with a solid Tantalum, with the total capacitance split about 75/25% with the Aluminum being the larger value. If two capacitors are paralleled, the effective ESR is the parallel of the two individual values. The "flatter" ESR of the Tantalum will keep the effective ESR from rising as quickly at low temperatures. HEATSINKING TO-220 PACKAGE PARTS The TO-220 can be attached to a typical heatsink, or secured to a copper plane on a PC board. If a copper plane is to be used, the values of (J-A) will be the same as shown in the next section for the TO-263. If a manufactured heatsink is to be selected, the value of heatsink-to-ambient thermal resistance, (H-A), must first be calculated: (H-A) = (J-A) - (C-H) - (J-C) Where: (J-C) is defined as the thermal resistance from the junction to the surface of the case. A value of 3C/W can be assumed for (J-C) for this calculation. (C-H) is defined as the thermal resistance between the case and the surface of the heatsink. The value of (C-H) will vary from about 1.5C/W to about 2.5C/W (depending on method of attachment, insulator, etc.). If the exact value is unknown, 2C/W should be assumed for (C-H). HEATSINKING A heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the application. Under all possible operating conditions, the junction temperature must be within the range specified under Absolute Maximum Ratings. To determine if a heatsink is required, the power dissipated by the regulator, PD, must be calculated. www.national.com 8 (Continued) Figure 5 and Figure 6 show the information for the SOT-223 package. Figure 6 assumes a (J-A) of 74C/W for 1 ounce copper and 51C/W for 2 ounce copper and a maximum junction temperature of +85C. When a value for (H-A) is found using the equation shown, a heatsink must be selected that has a value that is less than or equal to this number. (H-A) is specified numerically by the heatsink manufacturer in the catalog, or shown in a curve that plots temperature rise vs power dissipation for the heatsink. HEATSINKING TO-263 AND SOT-223 PACKAGE PARTS Both the TO-263 ("S") and SOT-223 ("MP") packages use a copper plane on the PCB and the PCB itself as a heatsink. To optimize the heat sinking ability of the plane and PCB, solder the tab of the package to the plane. Figure 3 shows for the TO-263 the measured values of (J-A) for different copper area sizes using a typical PCB with 1 ounce copper and no solder mask over the copper area used for heatsinking. 10011322 FIGURE 5. (J-A) vs Copper (2 ounce) Area for the SOT-223 Package 10011320 FIGURE 3. (J-A) vs Copper (1 ounce) Area for the TO-263 Package As shown in the figure, increasing the copper area beyond 1 square inch produces very little improvement. It should also be observed that the minimum value of (J-A) for the TO-263 package mounted to a PCB is 32C/W. As a design aid, Figure 4 shows the maximum allowable power dissipation compared to ambient temperature for the TO-263 device (assuming (J-A) is 35C/W and the maximum junction temperature is 125C). 10011323 FIGURE 6. Maximum Power Dissipation vs TAMB for the SOT-223 Package Please see AN1028 for power enhancement techniques to be used with the SOT-223 package. SOT-223 SOLDERING RECOMMENDATIONS It is not recommended to use hand soldering or wave soldering to attach the small SOT-223 package to a printed circuit board. The excessive temperatures involved may cause package cracking. Either vapor phase or infrared reflow techniques are preferred soldering attachment methods for the SOT-223 package. 10011321 FIGURE 4. Maximum Power Dissipation vs TAMB for the TO-263 Package 9 www.national.com LM2937-2.5, LM2937-3.3 Application Hints LM2937-2.5, LM2937-3.3 Physical Dimensions inches (millimeters) unless otherwise noted Plastic Package Order Number LM2937ET-2.5, LM2937ET-3.3, NS Package Number T03B TO-263 3-Lead Plastic Surface Mount Package Order Number LM2937ES-2.5, LM2937ES-3.3, NS Package Number TS3B www.national.com 10 inches (millimeters) unless otherwise noted (Continued) SOT-223 3-Lead Plastic Surface Mount Package Order Number LM2937IMP-2.5, LM2937IMP-3.3, NS Package Number MA04A National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. For the most current product information visit us at www.national.com. LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ``Banned Substances'' as defined in CSP-9-111S2. Leadfree products are RoHS compliant. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Francais Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 LM2937-2.5, LM2937-3.3 400mA and 500mA Voltage Regulators Physical Dimensions IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Audio www.ti.com/audio Communications and Telecom www.ti.com/communications Amplifiers amplifier.ti.com Computers and Peripherals www.ti.com/computers Data Converters dataconverter.ti.com Consumer Electronics www.ti.com/consumer-apps DLP(R) Products www.dlp.com Energy and Lighting www.ti.com/energy DSP dsp.ti.com Industrial www.ti.com/industrial Clocks and Timers www.ti.com/clocks Medical www.ti.com/medical Interface interface.ti.com Security www.ti.com/security Logic logic.ti.com Space, Avionics and Defense www.ti.com/space-avionics-defense Power Mgmt power.ti.com Transportation and Automotive www.ti.com/automotive Microcontrollers microcontroller.ti.com Video and Imaging RFID www.ti-rfid.com OMAP Mobile Processors www.ti.com/omap Wireless Connectivity www.ti.com/wirelessconnectivity TI E2E Community Home Page www.ti.com/video e2e.ti.com Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright (c) 2011, Texas Instruments Incorporated