LM3940 1-A Low-Dropout Regulator for 5-V to 3.3-V Conversion ...
Product Folder
Order Now
Technical Documents
Tools & Software
Support & Community
LM3940
SNVS114G ? MAY 1999 ? REVISED FEBRUARY 2015
LM3940 1-A Low-Dropout Regulator for 5-V to 3.3-V Conversion
1 Features
?1 Input Voltage Range: 4.5 V to 5.5 V ? Output Voltage Specified over Temperature ? Excellent Load Regulation ? Specified 1-A Output Current ? Requires only One External Component ? Built-in Protection against Excess Temperature ? Short-Circuit Protected
2 Applications
? Laptop and Desktop Computers ? Logic Systems
3 Description
The LM3940 is a 1-A low-dropout regulator designed to provide 3.3 V from a 5-V supply.
The LM3940 is ideally suited for systems which contain both 5-V and 3.3-V logic, with prime power provided from a 5-V bus.
Because the LM3940 is a true low dropout regulator, it can hold its 3.3-V output in regulation with input voltages as low as 4.5 V.
The TO-220 package of the LM3940 means that in most applications the full 1 A of load current can be delivered without using an additional heatsink.
The surface mount DDPAK/TO-263 package uses minimum board space, and gives excellent power dissipation capability when soldered to a copper plane on the PC board.
Device Information(1)
PART NUMBER PACKAGE
BODY SIZE (NOM)
SOT-223 (4)
6.50 mm x 3.50 mm
LM3940
DDPAK/TO-263 (3) 10.18 mm x 8.41 mm
TO-220 (3)
14.986 mm x 10.16 mm
(1) For all available packages, see the orderable addendum at the end of the datasheet.
Simplified Schematic
*Required if regulator is located more than 1 inch from the power supply filter capacitor or if battery power is used. **See Application and Implementation.
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM3940
SNVS114G ? MAY 1999 ? REVISED FEBRUARY 2015
Table of Contents
1 Features .................................................................. 1 2 Applications ........................................................... 1 3 Description ............................................................. 1 4 Revision History..................................................... 2 5 Pin Configuration and Functions ......................... 3 6 Specifications......................................................... 4
6.1 Absolute Maximum Ratings ...................................... 4 6.2 ESD Ratings.............................................................. 4 6.3 Recommended Operating Conditions....................... 4 6.4 Thermal Information .................................................. 4 6.5 Electrical Characteristics........................................... 5 6.6 Typical Characteristics .............................................. 6 7 Detailed Description .............................................. 8 7.1 Overview ................................................................... 8 7.2 Functional Block Diagram ......................................... 8 7.3 Feature Description................................................... 8 7.4 Device Functional Modes.......................................... 8
8 Application and Implementation .......................... 9 8.1 Application Information.............................................. 9 8.2 Typical Application .................................................... 9
9 Power Supply Recommendations...................... 11 10 Layout................................................................... 11
10.1 Layout Guidelines ................................................. 11 10.2 Layout Example .................................................... 11 10.3 Heatsinking ........................................................... 11 11 Device and Documentation Support ................. 15 11.1 Documentation Support ........................................ 15 11.2 Receiving Notification of Documentation Updates 15 11.3 Community Resources.......................................... 15 11.4 Trademarks ........................................................... 15 11.5 Electrostatic Discharge Caution ............................ 15 11.6 Glossary ................................................................ 15 12 Mechanical, Packaging, and Orderable Information ........................................................... 15
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision F (November 2014) to Revision G
Page
? Changed pin names to TI nomenclature ................................................................................................................................ 1 ? Deleted soldering information from Ab Max; this info is in POA ........................................................................................... 4 ? Changed Handling Ratings table to ESD Ratings table; move storage temp to Ab Max ...................................................... 4 ? Changed values in Input supply voltage row, ROC table ...................................................................................................... 4 ? Changed IL to IOUT .................................................................................................................................................................. 5
Changes from Revision E (March 2013) to Revision F
Page
? Added Device Information and Handling Rating tables, Feature Description, Device Functional Modes, Application and Implementation, Power Supply Recommendations, Layout, Device and Documentation Support, and Mechanical, Packaging, and Orderable Information sections; moved some curves to Application Curves section; update thermal values ............................................................................................................................................................ 1
Changes from Revision D (March 2013) to Revision E
Page
? Changed layout of National Data Sheet to TI format ........................................................................................................... 14
2
Submit Documentation Feedback
Product Folder Links: LM3940
Copyright ? 1999?2015, Texas Instruments Incorporated
5 Pin Configuration and Functions
3-Pin TO-220 Package
Front View
LM3940
SNVS114G ? MAY 1999 ? REVISED FEBRUARY 2015
4-Pin SOT-223 Front View
3-Pin DDPAK/TO-263 Package
Front View
NAME IN GND OUT
TO-220 1 2 3
PIN TO-263 1 2 3
Pin Functions
SOT-223 1
2, 4 3
I/O
DESCRIPTION
I
Input voltage supply. A 0.47-?F capacitor should be connected at this input.
--
Common ground
O
Output voltage. A 33-?F low ESR capacitor should be connected to this pin.
Copyright ? 1999?2015, Texas Instruments Incorporated
Product Folder Links: LM3940
Submit Documentation Feedback
3
LM3940
SNVS114G ? MAY 1999 ? REVISED FEBRUARY 2015
6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)(1)
Power dissipation(2)
Input supply voltage Storage temperature, Tstg
MIN
MAX
UNIT
Internally Limited
?0.3
7.5
V
-65
150
?C
(1) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
(2) The maximum allowable power dissipation is a function of the maximum junction temperature, TJ, the junction-to-ambient thermal resistance, RJA, 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 RJA (for devices in still air with no heatsink) is 23.3?C/W for the TO-220 package, 40.9?C/W for the DDPAK/TO-263 package, and 59.3?C/W for the SOT-223 package. The effective value of RJA can be reduced by using a heatsink (see Heatsinking for specific information on heatsinking).
6.2 ESD Ratings
V(ESD) Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) Charged-device model (CDM), per JEDEC specification JESD22C101 (2)
VALUE ?2000
?500
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. (2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
UNIT V
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
Junction temperature, TJ Input supply voltage, VIN
MIN
MAX UNIT
?40
125
?C
4.5
5.5
V
6.4 Thermal Information
LM3940
THERMAL METRIC(1)
SOT-223 (DCY)
TO-263 (KTT) TO-220 (NDE) UNIT
4 PINS
3 PINS
3 PINS
RJA RJC(top) RJB JT JB RJC(bot)
Junction-to-ambient thermal resistance, High-K Junction-to-case (top) thermal resistance Junction-to-board thermal resistance Junction-to-top characterization parameter Junction-to-board characterization parameter Junction-to-case (bottom) thermal resistance
59.3
40.9
23.3
?C/W
38.9
43.5
16.1
?C/W
8.1
23.5
4.8
?C/W
1.7
10.3
2.7
?C/W
8.0
22.5
4.8
?C/W
n/a
0.8
1.1
?C/W
(1) For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
4
Submit Documentation Feedback
Product Folder Links: LM3940
Copyright ? 1999?2015, Texas Instruments Incorporated
LM3940
SNVS114G ? MAY 1999 ? REVISED FEBRUARY 2015
6.5 Electrical Characteristics
Over operating free-air temperature range, VIN = 5 V, IOUT = 1 A, COUT = 33 F (unless otherwise noted). Limits apply for TJ = 25?C, unless otherwise specified in the Test Conditions column.(1)
VOUT
?VOUT ?VIN
?VOUT ?IOUT
ZOUT
PARAMETER Output voltage Line regulation Load regulation Output impedance
IQ
Quiescent current
TEST CONDITIONS
5 mA IOUT 1 A, TJ = 25?C
5 mA IOUT 1 A, ?40?C TJ 125?C
IOUT = 5 mA 4.5 V VIN 5.5 V
50 mA IOUT 1 A, TJ = 25?C
50 mA IOUT 1 A ?40?C TJ 125?C
IOUT (DC) = 100 mA IOUT (AC) = 20 mA (rms) = 120 Hz
4.5 V VIN 5.5 V, IOUT = 5 mA, TJ = 25?C
4.5 V VIN 5.5 V, IOUT = 5 mA ?40?C TJ 125?C
VIN = 5 V, IOUT = 1 A, TJ = 25?C
MIN
TYP
MAX
UNIT
3.20
3.3
3.40
V
3.13
3.47
20
40
35
50
mV
35
80
35
m
10
15
10
20
mA
110
200
en
Output noise voltage
VDO IOUT(SC)
Dropout voltage(2) Short-circuit current
VIN = 5 V, IOUT = 1 A ?40?C TJ 125?C
BW = 10 Hz ? 100 kHz IOUT = 5 mA
IOUT = 1 A, TJ = 25?C
IOUT = 1 A ?40?C TJ 125?C
IOUT = 100 mA, TJ = 25?C
IOUT = 100 mA ?40?C TJ 125?C
RL = 0
110
250
150
V(rms)
0.5
0.8
V
0.5
1
110
150
mV
110
200
1.2
1.7
A
(1) All limits specified for TJ = 25?C are 100% tested and are used to calculate Outgoing Quality Levels. All limits at temperature extremes are verified via correlation using standard Statistical Quality Control (SQC) methods.
(2) 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 = 5 V.
Copyright ? 1999?2015, Texas Instruments Incorporated
Product Folder Links: LM3940
Submit Documentation Feedback
5
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related download
- lm1117 800 ma low dropout linear regulator datasheet rev q
- 3 5 service characteristics department of drug and alcohol
- lm1085 3 a low dropout positive regulators datasheet rev h
- lm3940 1 a low dropout regulator for 5 v to 3 3 v conversion
- muscle grading and testing procedures national institute of
- ltc1844 series 150ma micropower low noise vldo linear
- exhibit 3 5 sample citizenship declaration