SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr February 2012 Rev. 1.0.0 GENERAL DESCRIPTION APPLICATIONS The SPX3940 is a 1A, accurate voltage  Power Supplies regulator with a low drop out voltage of  LCD Monitors 280mV (typical) at 1A.  Portable Instrumentation These regulators are specifically designed for low voltage applications that require a low  Medical and Industrial Equipments dropout voltage and a fast transient response. They are fully fault protected against over- FEATURES current, reverse battery, and positive and negative voltage transients.  Guaranteed 1.5A Peak Current The SPX3940 is offered in 3-pin SOT223 and  1% Output Accuracy SPX3940A TO-263 packages. For a 3A version, refer to  Low Quiescent Current the SPX29300 data sheet.  Low Dropout Voltage of 280mV at 1A  Extremely Tight Load and Line Regulation  Extremely Fast Transient Response  Reverse-battery Protection  Internal Thermal Protection  Internal Short Circuit Current Limit  Replacement for LM3940  Standard SOT223 & TO-263 packages TYPICAL APPLICATION DIAGRAM Fig. 1: SPX3940 Application Diagram – Fixed Output Linear Regulator Exar Corporation www.exar.com 48720 Kato Road, Fremont CA 94538, USA Tel. +1 510 668-7000 – Fax. +1 510 668-7001

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr ABSOLUTE MAXIMUM RATINGS OPERATING RATINGS These are stress ratings only and functional operation of Input Voltage V .................................................... 16V IN the device at these ratings or any other above those Junction Temperature Range ....................-40°C to 125°C indicated in the operation sections of the specifications Packages Thermal Resistance below is not implied. Exposure to absolute maximum SOT-223 Junction to Case (at T ) ..................... 15°C/W rating conditions for extended periods of time may affect A reliability. SOT-223 Junction to Ambient ........................62.3°C/W TO-263 Junction to Case (at T ) ......................... 3°C/W Input Voltage V ................................................... 20V1 A IN TO-263 Junction to Ambient ..........................31.4°C/W Storage Temperature .............................. -65°C to 150°C Lead Temperature (Soldering, 5 sec) ..................... 260°C Note 1: Maximum positive supply voltage of 20V must be of limited duration (<100ms) and duty cycle (<1%). The maximum continuous supply voltage is 16V. ELECTRICAL SPECIFICATIONS Specifications with standard type are for an Operating Ambient Temperature of T = 25°C only; limits applying over the full A Operating Junction Temperature range are denoted by a “•”. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at T = 25°C, and are provided A for reference purposes only. Unless otherwise indicated, V = V +1V, I = 10mA, C = 6.8µF, C = 10µF, T = 25°C. IN IN OUT IN OUT A Parameter Min. Typ. Max. Units Conditions 1.8V version 1.782 1.8 1.818 Output Voltage - SPX3940A (1%) V 1.755 1.8 1.845 • I =10mA OUT 1.764 1.8 1.836 10mA≤IOUT≤1A, 6V≤VIN≤16V Output Voltage - SPX3940 (2%) V 1.737 1.8 1.863 • 2.5V version 2.475 2.5 2.525 Output Voltage - SPX3940A (1%) V 2.437 2.5 2.563 • I =10mA OUT 2.450 2.5 2.550 10mA≤IOUT≤1A, 6V≤VIN≤16V Output Voltage - SPX3940 (2%) V 2.412 2.5 2.588 • 3.3V version 3.267 3.3 3.333 Output Voltage - SPX3940A (1%) V 3.217 3.3 3.383 • I =10mA OUT 3.234 3.3 3.366 10mA≤IOUT≤1A, 6V≤VIN≤16V Output Voltage - SPX3940 (2%) V 3.184 3.3 3.416 • 5.0V version 4.950 5.0 5.050 Output Voltage - SPX3940A (1%) V 4.875 5.0 5.125 • I =10mA OUT 4.900 5.0 5.100 10mA≤IOUT≤1A, 6V≤VIN≤16V Output Voltage - SPX3940 (2%) V 4.825 5.0 5.175 • All Voltage Options Line Regulation 0.2 1.0 % IOUT=10mA, (VOUT +1V)≤VIN≤16V Load Regulation 0.3 1.5 % VIN = VOUT +1V,10mA≤IOUT≤1A - Output Voltage 20 100 ppm/°C • temperature Coefficient Dropout Voltage2 70 200 mV • IOUT=100mA (except 1.8V version) 280 550 mV • IOUT=1A Ground Current3 12 25 mA • IOUT=750mA, VIN = VOUT +1V 18 mA IOUT=1A I Ground Pin Current at DGrNoDpDOout 1.2 mA VIN = 0.1V less than specified VOUT IOUT=10mA, Current Limit 1.5 2.2 A VOUT = 0V4 Output Noise Voltage 400 µVRMS 10Hz-100KHz, IL=100mA, CL=10µF 260 µVRMS 10Hz-100KHz, IL=100mA, CL=33µF © 2012 Exar Corporation 2/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr Note 2: Dropout voltage is defined as the input to output differential when the output voltage drops to 99% of its normal value. Note 3: Ground pin current is the regulator quiescent current. The total current drawn from the source is the sum of the load current to the ground current. Note 4: V =V +1V. For example, use V =4.3V for a 3.3V regulator. Employ pulse-testing procedures to minimize IN OUT(NOMINAL) IN temperature rise. BLOCK DIAGRAM Fig. 2: SPX3940 Block Diagram PIN ASSIGNMENT Fig. 3: SPX3940 Pin Assignment © 2012 Exar Corporation 3/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr ORDERING INFORMATION Temperature Packing Part Number Marking Package Note 1 Note 2 Range Quantity SPX3940AM3-L-1-8 3940A 2.5K/Tape & Reel 3-pin 1.8V Output -40°C≤T≤+125°C 18YYWWL Lead Free SPX3940AM3-L-1-8/TR J SOT-223 Bulk Voltage – 1% XXX SPX3940AM3-L-2-5 3940A 2.5K/Tape & Reel 3-pin 2.5V Output -40°C≤T≤+125°C 25YYWWL Lead Free SPX3940AM3-L-2-5/TR J SOT-223 Bulk Voltage – 1% XXX SPX3940AM3-L-3-3 3940A 2.5K/Tape & Reel 3-pin 3.3V Output -40°C≤T≤+125°C 33YYWWL Lead Free SPX3940AM3-L-3-3/TR J SOT-223 Bulk Voltage – 1% XXX SPX3940AM3-L-5-0 3940A 2.5K/Tape & Reel 3-pin 5.0V Output -40°C≤T≤+125°C 50YYWWL Lead Free SPX3940AM3-L-5-0/TR J SOT-223 Bulk Voltage – 1% XXX SPX3940AT-L-1-8 SPX3940AT 3-pin 500/Tape & Reel 1.8V Output -40°C≤T≤+125°C Lead Free SPX3940AT-L-1-8/TR J 18YYWWLX TO-263 Bulk Voltage – 1% SPX3940AT-L-3-3 SPX3940AT 3-pin 500/Tape & Reel 3.3V Output -40°C≤T≤+125°C Lead Free SPX3940AT-L-3-3/TR J 33YYWWLX TO-263 Bulk Voltage – 1% SPX3940AT-L-5-0 SPX3940AT 3-pin 500/Tape & Reel 5.0V Output -40°C≤T≤+125°C Lead Free SPX3940AT-L-5-0/TR J 50YYWWLX TO-263 Bulk Voltage – 1% SPX3940M3-L-2-5 3940M3 3-pin 2.5K/Tape & Reel 2.5V Output -40°C≤T≤+125°C Lead Free SPX3940M3-L-2-5/TR J 25YYWWL SOT-223 Bulk Voltage – 2% SPX3940M3-L-3-3 3940M3 3-pin 2.5K/Tape & Reel 3.3V Output -40°C≤T≤+125°C Lead Free SPX3940M3-L-3-3/TR J 33YYWWL SOT-223 Bulk Voltage – 2% SPX3940M3-L-5-0 3940M3 3-pin 2.5K/Tape & Reel 5.0V Output -40°C≤T≤+125°C Lead Free SPX3940M3-L-5-0/TR J 50YYWWL SOT-223 Bulk Voltage – 2% SPX3940T-L-3-3 SPX3940T 3-pin 500/Tape & Reel 3.3V Output -40°C≤T≤+125°C Lead Free SPX3940T-L-3-3/TR J 33YYWWLX TO-263 Bulk Voltage – 2% SPX3940T-L-5-0 SPX3940T 3-pin 500/Tape & Reel 5.0V Output -40°C≤T≤+125°C Lead Free SPX3940T-L-5-0/TR J 33YYWWLX TO-263 Bulk Voltage – 2% “YY” = Year – “WW” = Work Week – “X” = Lot Number – when applicable. © 2012 Exar Corporation 4/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr TYPICAL PERFORMANCE CHARACTERISTICS Schematic and BOM from Application Information section of this datasheet. Fig. 4: Line Regulation Fig. 5: Load Regulation Fig. 6: Ground Current vs Load Current Fig. 7: Ground Current vs Input Voltage Fig. 8: Ground Current vs Load Current in Dropout Fig. 9: Dropout Voltage vs Load Current © 2012 Exar Corporation 5/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr Fig. 10: Ground Current vs Temperature Fig. 11: Output Voltage vs Temperature I =100mA I =100mA LOAD LOAD Fig. 12: Ground Current vs Temperature Fig. 13: Ground Current vs Temperature I =500mA Dropout, I =750mA LOAD LOAD Fig. 14: Ground Current vs Temperature Fig. 15: Ground Current vs Temperature I =1.5A Dropout, I =1.5A LOAD LOAD © 2012 Exar Corporation 6/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr Fig. 16: Dropout Voltage vs Temperature Fig. 17: Dropout Voltage vs Temperature I =750mA I =1.5A LOAD LOAD Fig. 18: Enable Current vs Temperature Fig. 19: Enable Threshold vs Temperature V =16V EN © 2012 Exar Corporation 7/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr THEORY OF OPERATION T = T + P * (θ + θ + θ ) or J A D HA CH JC The SPX3940 incorporates protection against T = 50 + 7.5 * (1 + 2 + 3) = 95°C J over-current faults, reversed load insertion, Reliable operation is insured. over temperature operation, and positive and negative transient voltage. CAPACITOR REQUIREMENTS THERMAL CONSIDERATIONS The output capacitor is needed to insure stability and minimize the output noise. The Although the SPX3940 offers limiting circuitry value of the capacitor varies with the load. for overload conditions, it is still necessary to However, a minimum value of 10µF aluminum insure that the maximum junction capacitor will guarantee stability over all load temperature is not exceeded in the conditions. A tantalum capacitor is application. Heat will flow through the lowest recommended if a faster load transient resistance path, the junction-to-case path. In response is needed. order to insure the best thermal flow of the component, proper mount-ing is required. If the power source has a high AC impedance, Consult heatsink manufacturer for thermal a 0.1µF ceramic capacitor between input & resistance and design of heatsink. ground is recommended. TO-220 Design Example: MINIMUM LOAD CURRENT Assume that V = 10V, V = 5V, To ensure a proper behavior of the regulator IN OUT I = 1.5A, T = 50°C/W, θ = 1°C/W, under light load, a minimum load of 5mA for OUT A HA θ = 2°C/W, and θ = 3°C/W. SPX3940 is required. CH JC Where T = ambient temperature A θ = heatsink to ambient thermal resistance HA θ = case to heatsink thermal resistance CH θ = junction to case thermal resistance JC The power calculated under these conditions is: Fig. 20: Fixed Output Linear Regulator P = (V – V ) * I = 7.5W. D IN OUT OUT And the junction temperature is calculated as © 2012 Exar Corporation 8/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr PACKAGE SPECIFICATION 3-PIN SOT-223 © 2012 Exar Corporation 9/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr 3-PIN TO-263 © 2012 Exar Corporation 10/11 Rev. 1.0.0

SSPPXX33994400 11AA LLooww DDrrooppoouutt VVoollttaaggee RReegguullaattoorr REVISION HISTORY Revision Date Description A 04/14/2006 Reformat of Datasheet 1.0.0 02/29/2012 Package drawing corrections FOR FURTHER ASSISTANCE Email: customersupport@exar.com Exar Technical Documentation: http://www.exar.com/TechDoc/default.aspx? EXAR CORPORATION HEADQUARTERS AND SALES OFFICES 48720 Kato Road Fremont, CA 94538 – USA Tel.: +1 (510) 668-7000 Fax: +1 (510) 668-7030 www.exar.com NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained here in are only for illustration purposes and may vary depending upon a user’s specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited. © 2012 Exar Corporation 11/11 Rev. 1.0.0