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Part: LM3940ISX-3.3
Category:
Power Management
-> Regulators
-> Linear Voltage Regulators
-> LDO (Low Drop Out)
-> Positive Voltage->Fixed
Description: LM3940 - ia Low Dropout Regulator For 5V to 3.3V Conversion, Package: SOT-223, Pin Nb=4
Company: National Semiconductor Corporation
Datasheet: Download LM3940ISX-3.3 datasheet File size : 4 kB
Request For quote: Find where to buy LM3940ISX-3.3
Datasheet text preview:
LM3940 1A Low Dropout Regulator for 5V to 3.3V Conversion
January 2003
LM3940 1A Low Dropout Regulator for 5V to 3.3V Conversion
General Description
The LM3940 is a 1A low dropout regulator designed to provide 3.3V from a 5V supply. The LM3940 is ideally suited for systems which contain both 5V and 3.3V logic, with prime power provided from a 5V bus. Because the LM3940 is a true low dropout regulator, it can hold its 3.3V output in regulation with input voltages as low as 4.5V. The T0-220 package of the LM3940 means that in most applications the full 1A of load current can be delivered without using an additional heatsink. The surface mount TO-263 package uses minimum board space, and gives excellent power dissipation capability when soldered to a copper plane on the PC board.
Features
n n n n n n Output voltage specified over temperature Excellent load regulation Guaranteed 1A output current Requires only one external component Built-in protection against excess temperature Short circuit protected
Applications
n Laptop/Desktop Computers n Logic Systems
Typical Application
01208001
*Required if regulator is located more than 1" from the power supply filter capacitor or if battery power is used. **See Application Hints.
Connection Diagram/Ordering Information
01208002
01208010
3-Lead TO-220 Package (Front View) Order Part Number LM3940IT-3.3 NSC Drawing Number TO3B
3-Lead SOT-223 (Front View) Order Part Number LM3940IMP-3.3 Package Marked L52B NSC Drawing Number MP04A
01208003
3-Lead TO-263 Package (Front View) Order Part Number LM3940IS-3.3 NSC Drawing Number TS3B
© 2003 National Semiconductor Corporation
DS012080
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LM3940
Connection Diagram/Ordering Information (Continued)
8-Lead LLP
01208030
Pin 2 and pin 7 are fused to center DAP
01208027
Pin 5 and 6 need to be tied together on PCB board
16-Lead Ceramic Dual-in-Line Package (Top View) Order Part Number LM3940J-3.3-QML 5962-9688401QEA NSC Drawing Number J16A
(Top View) Order Part Number LM3940LD-3.3 NSC Drawing Number LDC08A
01208028
16-Lead Ceramic Surface-Mount Package (Top View) Order Part Number LM3940WG-3.3-QML 5962-9688401QXA NSC Drawing Number WG16A
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LM3940
Absolute Maximum Ratings
(Note 1)
Lead Temperature (Soldering, 5 seconds) Power Dissipation (Note 2) Input Supply Voltage ESD Rating (Note 3)
260°C 7.5V 2 kV
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Storage Temperature Range -65°C to +150°C
Internally Limited
Operating Junction Temperature Range -40°C to +125°C
Electrical Characteristics
Limits in standard typeface are for TJ = 25°C, and limits in boldface type apply over the full operating temperature range. Unless otherwise specified: VIN = 5V, IL = 1A, COUT = 33 µF. Symbol VO Parameter Output Voltage Line Regulation Conditions 5 mA IL 1A IL = 5 mA 4.5V VO 5.5V Load Regulation 50 mA IL 1A 35 50 80 ZO Output Impedance IL (DC) = 100 mA IL (AC) = 20 mA (rms) f = 120 Hz IQ Quiescent Current 4.5V VIN 5.5V IL = 5 mA VIN = 5V IL = 1A en VO - VIN Output Noise Voltage Dropout Voltage (Note 5) IL = 100 mA IL(SC) Short Circuit Current RL = 0 110 1.7 1.2 BW = 10 Hz 100 kHz IL = 5 mA IL = 1A 0.5 0.8 1.0 150 200 A mV V 150 110 10 15 20 200 250 µV (rms) mA 35 m Typical 3.3 20 LM3940 (Note 4) min 3.20 3.13 max 3.40 3.47 40 mV V Units
Thermal Performance
Thermal Resistance Junction-to-Case Thermal Resistance Junction-to-Ambient 3-Lead TO-220 3-Lead TO-263 3-Lead TO-220 3-Lead TO-263 8-Lead LLP (Note 2) 4 4 60 80 35 °C/W °C/W °C/W °C/W °C/W
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the device outside of its rated operating conditions. Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ, the junction-to-ambient thermal resistance, JA, and the ambient temperature, TA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. The value of JA (for devices in still air with no heatsink) is 60°C/W for the TO-220 package, 80°C/W for the TO-263 package, and 174°C/W for the SOT-223 package. The effective value of JA can be reduced by using a heatsink (see Application Hints for specific information on heatsinking). The value of JA for the LLP package is specifically dependant on PCB trace area, trace material, and the number of layers and thermal vias. For improved thermal resistance and power dissipation for the LLP package, refer to Application Note AN-1187. It is recommended that 6 vias be placed under the center pad to improve thermal performance. Note 3: ESD rating is based on the human body model: 100 pF discharged through 1.5 k. Note 4: All limits guaranteed for TJ = 25°C are 100% tested and are used to calculate Outgoing Quality Levels. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods. Note 5: Dropout voltage is defined as the input-output differential voltage where the regulator output drops to a value that is 100 mV below the value that is measured at VIN = 5V.
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LM3940
Typical Performance Characteristics
Dropout Voltage Dropout Voltage vs. Temperature
01208013
01208014
Output Voltage vs. Temperature
Quiescent Current vs. Temperature
01208015
01208016
Quiescent Current vs. VIN
Quiescent Current vs. Load
01208017
01208018
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LM3940
Typical Performance Characteristics
Line Transient Response
(Continued) Load Transient Response
01208019
01208020
Ripple Rejection
Low Voltage Behavior
01208021
01208022
Output Impedance
Peak Output Current
01208023
01208024
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