Datasheet

ManualsBrandsUnbranded ManualsVoltage RegulatorsLM 2940 CT Low Drop Voltage Regulator, Positive

LM2940/LM2940C

1A Low Dropout Regulator

General Description

The LM2940/LM2940C positive voltage regulator features

the ability to source 1A of output current with a dropout volt-

age of typically 0.5V and a maximum of 1V over the entire

temperature range. Furthermore, a quiescent current reduc-

tion circuit has been included which reduces the ground cur-

rent when the differential between the input voltage and the

output voltage exceeds approximately 3V. The quiescent

current with 1A of output current and an input-output differ-

ential of 5V is therefore only 30 mA. Higher quiescent cur-

rents only exist when the regulator is in the dropout mode

−V

OUT

≤ 3V).

Designed also for vehicular applications, the LM2940/

LM2940C and all regulated circuitry are protected from re-

verse battery installations or 2-battery jumps. During line

transients, such as load dump when the input voltage can

momentarily exceed the specified maximum operating volt-

age, the regulator will automatically shut down to protect

both the internal circuits and the load. The LM2940/

LM2940C cannot be harmed by temporary mirror-image in-

sertion. Familiar regulator features such as short circuit and

thermal overload protection are also provided.

Features

n Dropout voltage typically 0.5V

n Output current in excess of 1A

n Output voltage trimmed before assembly

n Reverse battery protection

n Internal short circuit current limit

n Mirror image insertion protection

n P

Product Enhancement tested

Typical Application

Ordering Information

Temperature

Range

Output Voltage

Package

5.0 8.0 9.0 10 12 15

0˚C ≤ T

≤ 125˚C LM2940CT-5.0 LM2940CT-9.0 LM2940CT-12 LM2940CT-15 TO-220

LM2940CS-5.0 LM2940CS-9.0 LM2940CS-12 LM2940CS-15 TO-263

−40˚C ≤ T

≤ 125˚C LM2940T-5.0 LM2940T-8.0 LM2940T-9.0 LM2940T-10 LM2940T-12 TO-220

LM2940S-5.0 LM2940S-8.0 LM2940S-9.0 LM2940S-10 LM2940S-12 TO-263

−40˚C ≤ T

≤ 85˚C LM2940IMP-5.0 LM2940IMP-8.0 LM2940IMP-9.0 LM2940IMP-10 LM2940IMP-12 LM2940IMP-15 SOT-223

SOT-223 Package

Marking

L53B L54B L0EB L55B L56B L70B

−55˚C ≤ T

≤ 125˚C LM2940K-5.0/883 LM2940K-8.0/883 LM2940K-12/883 LM2940K-15/883 TO-3

The physical size of the SOT-223 is too small to contain the full device part number. The package markings indicated are what will appear on the actual device.

DS008822-3

Required if regulator is located far from power supply filter.

OUT

must be at least 22 µF to maintain stability. May be increased without bound to maintain regulation during transients. Locate as close as possible

to the regulator. This capacitor must be rated over the same operating temperature range as the regulator and the ESR is critical; see curve.

December 1997

LM2940/LM2940C 1A Low Dropout Regulator

Summary of content (18 pages)

PAGE 1
LM2940/LM2940C 1A Low Dropout Regulator momentarily exceed the specified maximum operating voltage, the regulator will automatically shut down to protect both the internal circuits and the load. The LM2940/ LM2940C cannot be harmed by temporary mirror-image insertion. Familiar regulator features such as short circuit and thermal overload protection are also provided.
PAGE 2
Absolute Maximum Ratings (Notes 2, 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
PAGE 3
Electrical Characteristics (Continued) VIN = VO + 5V, IO = 1A, CO = 22 µF, unless otherwise specified. Boldface limits apply over the entire operating temperature range of the indicated device.
PAGE 4
Electrical Characteristics (Continued) VIN = VO + 5V, IO = 1A, CO = 22 µF, unless otherwise specified. Boldface limits apply over the entire operating temperature range of the indicated device. All other specifications apply for TA = TJ = 25˚C Output Voltage (VO) 9V 10V LM2940 Parameter Conditions Typ Limit LM2940 Typ (Note 5) Dropout Voltage Short Circuit Units Limit (Note 5) IO = 1A IO = 100 mA 0.5 0.8/1.0 0.5 0.8/1.0 VMAX 110 150/200 110 150/200 mVMAX (Note 7) 1.9 1.6 1.9 1.
PAGE 5
Electrical Characteristics (Continued) VIN = VO + 5V, IO = 1A, CO = 22 µF, unless otherwise specified. Boldface limits apply over the entire operating temperature range of the indicated device.
PAGE 6
Typical Performance Characteristics Dropout Voltage Dropout Voltage vs Temperature Output Voltage vs Temperature DS008822-13 DS008822-14 Quiescent Current vs Temperature DS008822-15 Quiescent Current Quiescent Current DS008822-18 DS008822-17 DS008822-16 Line Transient Response Load Transient Response DS008822-20 DS008822-19 www.national.
PAGE 7
Typical Performance Characteristics (Continued) Maximum Power Dissipation (TO-220) Output Impedance Maximum Power Dissipation (TO-3) DS008822-22 DS008822-23 DS008822-24 Maximum Power Dissipation (TO-263) See (Note 3) DS008822-10 7 www.national.
PAGE 8
Typical Performance Characteristics (Continued) Low Voltage Behavior Low Voltage Behavior DS008822-25 Low Voltage Behavior Low Voltage Behavior Output at Voltage Extremes Low Voltage Behavior DS008822-30 DS008822-29 Output at Voltage Extremes DS008822-31 Output at Voltage Extremes DS008822-27 DS008822-26 DS008822-28 Output at Voltage Extremes DS008822-32 Output at Voltage Extremes DS008822-34 www.national.
PAGE 9
Typical Performance Characteristics (Continued) Output Capacitor ESR Peak Output Current DS008822-8 DS008822-6 Equivalent Schematic Diagram DS008822-1 Application Hints 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.
PAGE 10
Application Hints (Continued) Output Capacitor ESR DS008822-37 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) DS008822-6 where: TJ (max) is the maximum allowable junction temperature, which is 125˚C for commercial grade parts.
PAGE 11
Application Hints (Continued) 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 θ(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. DS008822-39 FIGURE 4.
PAGE 12
Connection Diagrams (TO-220) Plastic Package DS008822-2 Front View Order Number LM2940CT-5.0, LM2940CT-9.0, LM2940CT-12, LM2940CT-15, LM2940T-5.0, LM2940T-8.0, LM2940T-9.0, LM2940T-10 or LM2940T-12 See NS Package Number TO3B TO-3 Metal Can Package (K) DS008822-7 Bottom View Order Number LM2940K-5.0/883, LM2940K-8.0/883, LM2940K-12/883, LM2940K-15/883 See NS Package Number K02A www.national.
PAGE 13
Connection Diagrams (Continued) (TO-263) Surface-Mount Package DS008822-11 Top View DS008822-12 Side View Order Number LM2940CS-5.0, LM2940CS-9.0, LM2940CS-12, LM2940CS-15, LM2940S-5.0, LM2940S-8.0, LM2940S-9.0, LM2940S-10 or LM2940S-12 See NS Package Number TS3B 3-Lead SOT-223 DS008822-42 (Front View) Order Part Number LM2940IMP-5.0 LM2940IMP-8.0 LM2940IMP-9.0 LM2940IMP-10 LM2940IMP-12 LM2940IMP-15 See NS Package Number MA04A 13 www.national.
PAGE 14
PAGE 15
Physical Dimensions inches (millimeters) unless otherwise noted 3-Lead SOT-223 Package Order Part Number LM2940IMP-5.0 LM2940IMP-8.0 LM2940IMP-9.0 LM2940IMP-10 LM2940IMP-12 LM2940IMP-15 NS Package Number MA04A 15 www.national.
PAGE 16
Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 2 Lead TO-3 Metal Can Package (K) Order Number LM2940K-5.0/883, LM2940K-8.0/883, LM2940K-12/883, LM2940K-15/883 NS Package Number K02A www.national.
PAGE 17
Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 3-Lead TO-220 Plastic Package (T) Order Number LM2940T-5.0, LM2940T-8.0, LM2940T-9.0, LM2940T-10, LM2940T-12, LM2940CT-5.0, LM2940CT-12 or LM2940CT-15 NS Package Number TO3B 17 www.national.
PAGE 18
LM2940/LM2940C 1A Low Dropout Regulator Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 3-Lead TO-263 Surface Mount Package Order Number LM2940S-5.0, LM2940S-8.0, LM2940S-9.0, LM2940S-10, LM2940S-12, LM2940CS-5.