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S P X2 9 4 0
1A Low Dropout Voltage Regulator
August 2009 Rev. 2.0.0
GENERAL DESCRIPTION
The SPX2940 is a 1A, accurate voltage regulators with a low drop out voltage of 280mV (typical) at 1A. These regulators are specifically designed for low voltage applications that require a low dropout voltage and a fast transient response. They are fully fault protected against overcurrent, reverse battery, and positive and negative voltage transients. The SPX2940 is offered in 3-pin TO-220 & TO263 packages. For a 3A version, refer to the SPX29300 data sheet.
APPLICATIONS
* Power Supplies * LCD Monitors * Portable Instrumentation * Medical and Industrial Equipments
FEATURES
* Guaranteed 1.5A Peak Current * Low Quiescent Current * 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 LM2940, MIC2940A, AS2940 * Standard TO-220 and TO-263 packages
TYPICAL APPLICATION DIAGRAM
Fig. 1: SPX2940 Application Diagram - Fixed Output Linear Regulator
Exar Corporation 48720 Kato Road, Fremont CA 94538, USA
www.exar.com Tel. +1 510 668-7000 - Fax. +1 510 668-7001
S P X2 9 4 0
1A Low Dropout Voltage Regulator
ABSOLUTE MAXIMUM RATINGS
These are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. Input Voltage VIN ................................................... 16V1 Storage Temperature .............................. -65C to 150C Lead Temperature (Soldering, 5 sec) ..................... 260C
OPERATING RATINGS
Junction Temperature Range ....................-40C to 125C TO-220 Package Thermal Resistance, Junction to Case (at TA) .......... 4C/W TO-263 Package Thermal Resistance, Junction to Case (at TA) .......... 4C/W 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 TA = 25C only; limits applying over the full 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 TA = 25C, and are provided for reference purposes only. Unless otherwise indicated, VIN = VIN +1V, IOUT = 10mA, CIN = 6.8F, COUT = 10F, TA = 25C. Parameter 5.0V version Output Voltage Line Regulation Load Regulation

Min. 4.850 4.750
Typ. 5.0 5.0 0.2 0.3 20 70 280 12 18 1.2 1.5 400 260
Max. 5.150 5.250 1.0 1.5 100 200 550 25
Units V V % % ppm/C mV mV mA mA mA * * * * IOUT=100mA IOUT=1A
Conditions IOUT=10mA 10mAIOUT1A, 6VVIN16V IOUT=10mA, (VOUT +1V)VIN16V VIN = VOUT +1V,10mAIOUT1A
*
- Output Voltage
temperature Coefficient Dropout Voltage2 (except 1.8V version) Ground Current3 IGNDDO Ground Pin Current at Dropout Current Limit Output Noise Voltage
IOUT=750mA, VIN = VOUT +1V IOUT=1A VIN = 0.1V less than specified VOUT IOUT=10mA, VOUT = 0V4 10Hz-100KHz, IL=100mA, CL=10F 10Hz-100KHz, IL=100mA, CL=33F
2.2
A VRMS VRMS
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: VIN=VOUT(NOMINAL)+1V. For example, use VIN=4.3V for a 3.3V regulator. Employ pulse-testing procedures to minimize temperature rise.
(c) 2009 Exar Corporation
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S P X2 9 4 0
1A Low Dropout Voltage Regulator
BLOCK DIAGRAM
Fig. 2: SPX2940 Block Diagram
PIN ASSIGNMENT
Fig. 3: SPX2940 Pin Assignment
ORDERING INFORMATION
Part Number Temperature Range Marking Package 3-pin TO-263 3-pin TO-220 Packing Quantity Note 1 Note 2 5.0V Output Voltage 5.0V Output Voltage
SPX2940T-L-5-0/TR -40CTJ+125C SPX2940U-L-5-0
SPX2940T 50YYWWLX SPX2940U -40CTJ+125C 50YYWWLX
500/Tape & Reel Lead Free Bulk Lead Free
"YY" = Year - "WW" = Work Week - "X" = Lot Number
(c) 2009 Exar Corporation
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Rev. 2.0.0
S P X2 9 4 0
1A Low Dropout Voltage Regulator
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 Current in Dropout
Fig. 9: Dropout Voltage vs Load Current
(c) 2009 Exar Corporation
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S P X2 9 4 0
1A Low Dropout Voltage Regulator
Fig. 10: Ground Current vs Temperature ILOAD=100mA
Fig. 11: Output Voltage vs Temperature ILOAD=100mA
Fig. 12: Ground Current vs Temperature ILOAD=500mA
Fig. 13: Ground Current vs Temperature Dropout, ILOAD=750mA
Fig. 14: Ground Current vs Temperature ILOAD=1.5A
Fig. 15: Ground Current vs Temperature Dropout, ILOAD=1.5A
(c) 2009 Exar Corporation
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S P X2 9 4 0
1A Low Dropout Voltage Regulator
Fig. 16: Dropout Voltage vs Temperature ILOAD=750mA
Fig. 17: Dropout Voltage vs Temperature ILOAD=1.5A
Fig. 18: Enable Current vs Temperature VEN=16V
Fig. 19: Enable Threshold vs Temperature
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1A Low Dropout Voltage Regulator
THEORY OF OPERATION
The SPX2940 incorporates protection against over-current faults, reversed load insertion, over temperature operation, and positive and negative transient voltage. recommended if a response is needed. faster load transient
If the power source has a high AC impedance, a 0.1F ceramic capacitor between input & ground is recommended.
THERMAL CONSIDERATIONS
Although the SPX2940 offers limiting circuitry for overload conditions, it is still necessary to insure that the maximum junction temperature is not exceeded in the application. Heat will flow through the lowest resistance path, the junction-to-case path. In order to insure the best thermal flow of the component, proper mounting is required. Since the case of the device is electrically connected to the output, the case must be electrically isolated using a thermally conductive spacer, which itself contributes some small additional thermal resistance. Consult heatsink manufacturer for thermal resistance and design of heatsink. TO-220 Design Example: Assume that VIN = 10V, VOUT = 5V, IOUT = 1.5A, TA = 50C/W, HA= 1C/W, CH = 2C/W, and JC = 3C/W. Where TA = ambient temperature HA = heatsink to ambient thermal resistance CH = case to heatsink thermal resistance JC = junction to case thermal resistance The power calculated under these conditions is: PD = (VIN - VOUT) * IOUT = 7.5W. And the junction temperature is calculated as TJ = TA + PD * (HA + CH + JC) or TJ = 50 + 7.5 * (1 + 2 + 3) = 95C Reliable operation is insured.
MINIMUM LOAD CURRENT
To ensure a proper behavior of the regulator under light load, a minimum load of 5mA for SPX2940 is required. consequat eu, consequat eu, ullamcorper pretium, magna. Aenean varius turpis sed metus. Donec erat. Nunc urna pede, accumsan sed, tristique non, lobortis sit amet, pede.
Fig. 20: Fixed Output Linear Regulator
Fig. 21: Ouput Cap ESR vs IOUT
CAPACITOR REQUIREMENTS
The output capacitor is needed to insure stability and minimize the output noise. The value of the capacitor varies with the load. However, a minimum value of 10F aluminum capacitor will guarantee stability over all load conditions. A tantalum capacitor is
(c) 2009 Exar Corporation 7/10
Fig. 22: 5.0VOUT PSSR VIN=10V, VOUT=5V COUT=22F, IOUT=10mA
Rev. 2.0.0
S P X2 9 4 0
1A Low Dropout Voltage Regulator
PACKAGE SPECIFICATION 3-PIN TO-263
(c) 2009 Exar Corporation
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S P X2 9 4 0
1A Low Dropout Voltage Regulator
3-PIN TO-220
(c) 2009 Exar Corporation
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Rev. 2.0.0
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1A Low Dropout Voltage Regulator
REVISION HISTORY
Revision F 2.0.0 Date 11/03/2007 08/06/2009 Reformat of Datasheet Updated JC values Description
FOR FURTHER ASSISTANCE
Email: Exar Technical Documentation: customersupport@exar.com 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 malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes 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. or its in all
(c) 2009 Exar Corporation
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Rev. 2.0.0

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