LM2940IMP-12全新原装原理图各脚功能电路原理芯片引脚定义-中国IC网-芯三七

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产品型号LM2940IMP-12的概述

LM2940IMP-12 概述 LM2940IMP-12 是一款低压降线性稳压器，具备高效率和低噪声特性，适用于各种电源管理应用。该芯片的主要功能是将较高的输入电压转换为稳定的输出电压，提供给负载使用。LM2940的设计使其在相对较低的输入电压下仍能稳定输出12V，且其低压降特性使得电源的损耗极小，从而能够有效提高电力转换效率。 LM2940稳压器广泛应用于电源分配、系统供电、汽车电子以及通信设备等领域。得益于其内置的过温保护和过流保护特性，LM2940不仅提升了安全性，还延长了设备的使用寿命。此外，该芯片的设计也非常适合在电池供电设备中使用，因其能够在较低电压下始终保持稳定的输出。 LM2940IMP-12 的详细参数 LM2940IMP-12的参数特性包括： - 输出电压：12V - 最大输入电压：26V - 输出电流：最高1A - 满载压降：250mV（典型值，在1A负载时） -...

产品型号LM2940IMP-12的Datasheet PDF文件预览

January 2003

LM2940/LM2940C

1A Low Dropout Regulator

General Description

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.

The LM2940/LM2940C positive voltage regulator features

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

voltage of typically 0.5V and a maximum of 1V over the

entire temperature range. Furthermore, a quiescent current

reduction circuit has been included which reduces the

ground current when the differential between the input volt-

age and the output voltage exceeds approximately 3V. The

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

output differential of 5V is therefore only 30 mA. Higher

quiescent currents only exist when the regulator is in the

dropout mode (V_IN− V_OUT≤ 3V).

Features

n Dropout voltage typically 0.5V I_O= 1A

n Output current in excess of 1A

n Output voltage trimmed before assembly

n Reverse battery protection

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

n Internal short circuit current limit

n Mirror image insertion protection

n P⁺Product Enhancement tested

Typical Application

00882203

Required if regulator is located far from power supply filter.

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

OUT

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

Ordering Information

Temperature

Range

Output Voltage

9.0

Package

5.0

8.0

0˚C ≤ T_J≤ 125˚C LM2940CT-5.0

LM2940CT-9.0

LM2940CS-9.0

LM2940CT-12

LM2940CS-12

LM2940CT-15

LM2940CS-15

LM2940LD-15

TO-220

TO-263

LM2940CS-5.0

−40˚C ≤ T_J

≤

LM2940LD-5.0

LM2940LD-8.0 LM2940LD-9.0

LM2940LD-10 LM2940LD-12

LLP 1k

Units

Tape and

Reel

125˚C

LM2940LDX-5.0

LM2940LDX-8.0 LM2940LDX-9.0

LM2940LDX-10 LM2940LDX-12 LM2940LDX-15

LLP 4.5k

Units

Tape and

Reel

−40˚C ≤ T_J

≤

LM2940T-5.0

LM2940S-5.0

LM2940T-8.0

LM2940S-8.0

LM2940T-9.0

LM2940S-9.0

LM2940T-10

LM2940S-10

LM2940T-12

LM2940S-12

TO-220

125˚C

TO-263

−40˚C ≤ T_J

LM2940IMP-5.0 LM2940IMP-8.0 LM2940IMP-9.0 LM2940IMP-10 LM2940IMP-12 LM2940IMP-15

SOT-223

85˚C

LM2940IMPX-5.0 LM2940IMPX-8.0 LM2940IMPX-9.0 LM2940IMPX-10 LM2940IMPX-12 LM2940IMPX-15 SOT-223

in Tape

and Reel

SOT-223

Package Marking

L53B

L54B

L0EB

L55B

L56B

L70B

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

www.national.com

Ordering Information (Continued)

Temperature

Range

Output Voltage

Package

J16A

5.0

8.0

−55˚C ≤ T_J≤ 125˚C

LM2940J-5.0/883

5962-8958701EA

LM2940WG5.0/883

5962-8958701XA

LM2940J-8.0/883

LM2940J-12/883

5962-9088401QEA

LM2940J-15/883

5962-9088501QEA

5962-9088301QEA

WG16A

For information on military temperature range products, please go to the Mil/Aero Web Site at http://www.national.com/appinfo/milaero/index.html.

Connection Diagrams

(TO-220) Plastic Package

3-Lead SOT-223

00882202

00882242

Front View

Order Part Number LM2940IMP-5.0,

LM2940IMP-8.0, LM2940IMP-9.0,

Order Number LM2940CT-5.0, LM2940CT-9.0,

LM2940CT-12, LM2940CT-15, LM2940T-5.0,

LM2940T-8.0, LM2940T-9.0,

LM2940IMP-10, LM2940IMP-12 or LM2940IMP-15

See NS Package Number MP04A

LM2940T-10 or LM2940T-12

See NS Package Number TO3B

16-Lead Ceramic Surface-Mount Package (WG)

16-Lead Dual-in-Line Package (J)

00882244

Top View

00882243

Top View

Order Number LM2940WG5.0/883 (5962-8958701XA)

See NS Package Number WG16A

Order Number LM2940J-5.0/883 (5962-8958701EA),

LM2940J-8.0/883 (5962-9088301QEA),

LM2940J-12/883 (5962-9088401QEA),

LM2940J-15/883 (5962-9088501QEA)

See NS Package Number J16A

www.national.com

Connection Diagrams (Continued)

(TO-263) Surface-Mount Package

8-Lead LLP

00882211

Top View

00882212

Side View

00882246

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

Top View

Order Number LM2940LD-5.0, LM2940LD-8.0,

LM2940LD-9.0, LM2940LD-10,

LM2940LD-12, LM2940LD-15

See NS Package Number LDC08A

Pin 2 and pin 7 are fused to center DAP

Pin 5 ans 6 need to be tied together on PCB board

www.national.com

Absolute Maximum Ratings (Note 1)

SOT-223 (MP) Package

260˚C, 4s

2 kV

ESD Susceptibility (Note 3)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Operating Conditions (Note 1)

Input Voltage

LM2940S, T, MP ≤ 100 ms

LM2940CS, T ≤ 1 ms

60V

45V

26V

Temperature Range

Internal Power Dissipation

(Note 2)

LM2940T, LM2940S

LM2940CT, LM2940CS

LM2940IMP

−40˚C ≤ T_J≤ 125˚C

0˚C ≤ T_J≤ 125˚C

Internally Limited

150˚C

Maximum Junction Temperature

Storage Temperature Range

−40˚C ≤ T_J≤ 85˚C

−55˚C ≤ T_J≤ 125˚C

−40˚C ≤ T_J≤ 125˚C

−65˚C ≤ T_J≤ +150˚C

LM2940J, LM2940WG

LM2940LD

Lead Temperature, Time for Wave Soldering

TO-220 (T) Package

260˚C, 10s

260˚C, 4s

TO-263 (S) Package

Electrical Characteristics

V_IN= V_O+ 5V, I_O= 1A, C_O= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-

ture range of the indicated device. All other specifications apply for T_A= T_J= 25˚C.

Output Voltage (V_O)

LM2940

LM2940/883

Limit

LM2940/883

Limit

Units

Parameter Conditions

Typ

Limit

Typ

Limit

(Note 4)

(Note 5)

(Note 4)

(Note 5)

6.25V ≤ V_IN≤ 26V

9.4V ≤ V_IN≤ 26V

Output Voltage

Line Regulation

Load Regulation

5 mA ≤ I_O≤ 1A

5.00

4.85/4.75

5.15/5.25

4.85/4.75

8.00

7.76/7.60

8.24/8.40

7.76/7.60

V_MIN

V_MAX

5.15/5.25

40/50

8.24/8.40

50/80

V_O+ 2V ≤ V_IN≤ 26V,

I_O= 5 mA

mV_MAX

50 mA ≤ I_O≤ 1A

LM2940, LM2940/883

LM2940C

50/80

50/100

80/130

mV_MAX

Output

100 mADC and

20 mArms,

Impedance

1000/1000

mΩ

f_O= 120 Hz

Quiescent

Current

V_O+2V ≤ V_IN≤ 26V,

I_O= 5 mA

LM2940, LM2940/883

LM2940C

15/20

50/60

15/20

45/60

15/20

50/60

mA_MAX

µV_rms

V_IN= V_O+ 5V,

I_O= 1A

45/60

Output Noise

Voltage

10 Hz − 100 kHz,

I_O= 5 mA

150

700/700

240

1000/1000

Ripple Rejection

f_O= 120 Hz, 1 V_rms

I_O= 100 mA

LM2940

60/54

54/48

dB_MIN

LM2940C

f_O= 1 kHz, 1 V_rms

60/50

54/48

I_O= 5 mA

Long Term

Stability

mV/

1000 Hr

V_MAX

Dropout Voltage

I_O= 1A

0.5

0.8/1.0

0.7/1.0

0.5

0.8/1.0

0.7/1.0

I_O= 100 mA

(Note 6)

110

150/200

110

150/200

mV_MAX

Short Circuit

Current

1.9

1.6

1.5/1.3

1.9

1.6

1.6/1.3

A_MIN

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Electrical Characteristics (Continued)

V_IN= V_O+ 5V, I_O= 1A, C_O= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-

ture range of the indicated device. All other specifications apply for T_A= T_J= 25˚C.

Output Voltage (V_O)

LM2940

LM2940/883

Limit

LM2940/883

Limit

Units

Parameter Conditions

Typ

Limit

Typ

Limit

(Note 4)

(Note 5)

(Note 4)

(Note 5)

Maximum Line

Transient

R_O= 100Ω

LM2940, T ≤ 100 ms

LM2940/883, T ≤ 20 ms

LM2940C, T ≤ 1 ms

R_O= 100Ω

60/60

V_MIN

40/40

Reverse Polarity

DC Input Voltage

LM2940, LM2940/883

LM2940C

−30

−15/−15

−30

−15/−15

V_MIN

−15

Reverse Polarity

Transient Input

Voltage

R_O= 100Ω

LM2940, T ≤ 100 ms

LM2940/883, T ≤ 20 ms

LM2940C, T ≤ 1 ms

−75

−55

−50/−50

−45/−45

−75

−50/−50

V_MIN

−45/−45

Electrical Characteristics

V_IN= V_O+ 5V, I_O= 1A, C_O= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-

ture range of the indicated device. All other specifications apply for T_A= T_J= 25˚C.

Output Voltage (V_O)

10V

LM2940

Limit

LM2940

Limit

Units

Parameter

Conditions

Typ

(Note 4)

10.5V ≤ V_IN≤ 26V

11.5V ≤ V_IN≤ 26V

Output Voltage

Line Regulation

Load Regulation

5 mA ≤ I_O≤1A

9.00

8.73/8.55

9.27/9.45

10.00

9.70/9.50

10.30/10.50

100

V_MIN

V_MAX

V_O+ 2V ≤ V_IN≤ 26V,

I_O= 5 mA

mV_MAX

50 mA ≤ I_O≤ 1A

LM2940

90/150

100/165

mV_MAX

LM2940C

Output Impedance

100 mADC and

20 mArms,

mΩ

f_O= 120 Hz

Quiescent

Current

V_O+2V ≤ V_IN26V,

I_O= 5 mA

LM2940

15/20

45/60

mA_MAX

LM2940C

V_IN= V_O+ 5V, I_O= 1A

10 Hz − 100 kHz,

I_O= 5 mA

45/60

mA_MAX

µV_rms

Output Noise

Voltage

270

300

Ripple Rejection

f_O= 120 Hz, 1 V_rms

I_O= 100 mA

LM2940

52/46

51/45

dB_MIN

LM2940C

Long Term

Stability

mV/

1000 Hr

V_MAX

Dropout Voltage

I_O= 1A

0.5

0.8/1.0

0.5

0.8/1.0

I_O= 100 mA

110

150/200

110

150/200

mV_MAX

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Electrical Characteristics (Continued)

V_IN= V_O+ 5V, I_O= 1A, C_O= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-

ture range of the indicated device. All other specifications apply for T_A= T_J= 25˚C.

Output Voltage (V_O)

Parameter Conditions

Short Circuit

10V

LM2940

Limit

LM2940

Limit

Units

Typ

(Note 4)

1.6

(Note 4)

1.6

(Note 6)

1.9

A_MIN

Current

Maximum Line

Transient

R_O= 100Ω

T ≤ 100 ms

LM2940

60/60

V_MIN

LM2940C

R_O= 100Ω

LM2940

Reverse Polarity

DC Input Voltage

−30

−15/−15

−30

−15/−15

V_MIN

LM2940C

R_O= 100Ω

T ≤ 100 ms

LM2940

−15

Reverse Polarity

Transient Input

Voltage

−75

−55

−50/−50

−45/−45

−75

−50/−50

V_MIN

LM2940C

Electrical Characteristics

V_IN= V_O+ 5V, I_O= 1A, C_O= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-

ture range of the indicated device. All other specifications apply for T_A= T_J= 25˚C.

Output Voltage (V_O)

12V

LM2940

15V

LM2940

LM2940/833

Limit

LM2940/833

Limit

Units

Parameter Conditions

Typ

Limit

Typ

Limit

(Note 4)

(Note 5)

(Note 4)

(Note 5)

13.6V ≤ V_IN≤ 26V

12.00 11.64/11.40 11.64/11.40 15.00 14.55/14.25 14.55/14.25

12.36/12.60 12.36/12.60 15.45/15.75 15.45/15.75

16.75V ≤ V_IN≤ 26V

Output Voltage

Line Regulation

Load Regulation

5 mA ≤ I_O≤1A

V_MIN

V_MAX

V_O+ 2V ≤ V_IN≤ 26V,

I_O= 5 mA

120

75/120

150

95/150

150/240

mV_MAX

50 mA ≤ I_O≤ 1A

LM2940, LM2940/883

LM2940C

120/200

120/190

mV_MAX

120

150

Output

100 mADC and

20 mArms,

Impedance

1000/1000

100

1000/1000

mΩ

f_O= 120 Hz

Quiescent

Current

V_O+2V ≤ V_IN≤ 26V,

I_O= 5 mA

LM2940, LM2940/883

LM2940C

15/20

mA_MAX

V_IN= V_O+ 5V, I_O= 1A

10 Hz − 100 kHz,

I_O= 5 mA

45/60

50/60

45/60

50/60

mA_MAX

µV_rms

Output Noise

Voltage

360

1000/1000

450

1000/1000

Ripple Rejection

f_O= 120 Hz, 1 V_rms

I_O= 100 mA

LM2940

54/48

dB_MIN

LM2940C

f_O= 1 kHz, 1 V_rms

52/46

48/42

I_O= 5 mA

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Electrical Characteristics (Continued)

V_IN= V_O+ 5V, I_O= 1A, C_O= 22 µF, unless otherwise specified. Boldface limits apply over the entire operating tempera-

ture range of the indicated device. All other specifications apply for T_A= T_J= 25˚C.

Output Voltage (V_O)

Parameter Conditions

Long Term

12V

LM2940

15V

LM2940

LM2940/833

Limit

LM2940/833

Limit

Units

Typ

Limit

Typ

Limit

(Note 4)

(Note 5)

(Note 4)

(Note 5)

mV/

1000 Hr

V_MAX

Stability

Dropout Voltage

I_O= 1A

0.5

0.8/1.0

0.7/1.0

0.5

0.8/1.0

0.7/1.0

I_O= 100 mA

(Note 6)

110

150/200

110

150/200

mV_MAX

Short Circuit

Current

1.9

1.6

1.6/1.3

1.9

1.6

1.6/1.3

A_MIN

Maximum Line

Transient

R_O= 100Ω

LM2940, T ≤ 100 ms

LM2940/883, T ≤ 20 ms

LM2940C, T ≤ 1 ms

R_O= 100Ω

60/60

40/40

V_MIN

Reverse Polarity

DC Input

LM2940, LM2940/883

LM2940C

−30

−15/−15

V_MIN

Voltage

−15

−30

−15

Reverse Polarity

Transient Input

Voltage

R_O= 100Ω

LM2940, T ≤ 100 ms

LM2940/883, T ≤ 20 ms

LM2940C, T ≤ 1 ms

−75

−55

−50/−50

−45/−45

V_MIN

−55

−45/−45

Thermal Performance

Thermal Resistance

3-Lead TO-220

˚C/W

Junction-to-Case

3-Lead TO-263

Thermal Resistance

Junction-to-Ambient

3-Lead TO-220

3-Lead TO-263

8-Lead LLP (Note 2)

Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Conditions are conditions under which the device functions

but the specifications might not be guaranteed. For guaranteed specifications and test conditions see the Electrical Characteristics.

Note 2: The maximum allowable power dissipation is a function of the maximum junction temperature, T , the junction-to-ambient thermal resistance, θ , and the

ambient temperature, T . Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown.

The value of θ (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 θ can be reduced by using a heatsink (see Application Hints for specific information on heatsinking). The value of θ for the LLP package

is specifically dependent 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 kΩ.

Note 4: All limits are guaranteed at T = T = 25˚C only (standard typeface) or over the entire operating temperature range of the indicated device (boldface type).

All limits at T = T = 25˚C are 100% production tested. All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control

methods.

Note 5: All limits are guaranteed at T = T = 25˚C only (standard typeface) or over the entire operating temperature range of the indicated device (boldface type).

All limits are 100% production tested and are used to calculate Outgoing Quality Levels.

Note 6: Output current will decrease with increasing temperature but will not drop below 1A at the maximum specified temperature.

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Typical Performance Characteristics

Dropout Voltage

Dropout Voltage vs. Temperature

00882213

00882214

Output Voltage vs. Temperature

Quiescent Current vs. Temperature

00882215

00882216

Quiescent Current

00882217

00882218

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Typical Performance Characteristics (Continued)

Line Transient Response

Load Transient Response

Low Voltage Behavior

00882220

00882219

Ripple Rejection

00882225

00882221

Low Voltage Behavior

00882226

00882227

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Typical Performance Characteristics (Continued)

Low Voltage Behavior

Output at Voltage Extremes

00882228

00882229

00882231

00882233

Low Voltage Behavior

00882230

Output at Voltage Extremes

00882232

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Typical Performance Characteristics (Continued)

Output at Voltage Extremes

00882234

00882235

Output at Voltage Extremes

Output Capacitor ESR

00882236

00882206

Peak Output Current

Output Impedance

00882222

00882208

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Typical Performance Characteristics (Continued)

Maximum Power Dissipation (TO-220)

Maximum Power Dissipation (TO-3)

00882224

00882223

Maximum Power Dissipation (TO-263)

See (Note 2)

00882210

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Equivalent Schematic Diagram

00882201

Application Hints

Output Capacitor ESR

EXTERNAL CAPACITORS

The output capacitor is critical to maintaining regulator sta-

bility, and must meet the required conditions for both ESR

(Equivalent Series Resistance) and minimum amount of ca-

pacitance.

MINIMUM CAPACITANCE:

The minimum output capacitance required to maintain sta-

bility is 22 µF (this value may be increased without limit).

Larger values of output capacitance will give improved tran-

sient response.

ESR LIMITS:

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 essen-

tial that the output capacitor meet these requirements,

or oscillations can result.

00882206

FIGURE 1. ESR Limits

It is important to note that for most capacitors, ESR is

specified only at room temperature. However, the designer

must ensure that the ESR will stay inside the limits shown

over the entire operating temperature range for the design.

For aluminum electrolytic capacitors, ESR will increase by

about 30X as the temperature is reduced from 25˚C to

−40˚C. This type of capacitor is not well-suited for low tem-

perature operation.

Solid tantalum capacitors have a more stable ESR over

temperature, but are more expensive than aluminum elec-

trolytics. A cost-effective approach sometimes used is to

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HEATSINKING TO-220 PACKAGE PARTS

Application Hints (Continued)

parallel an aluminum electrolytic with a solid Tantalum, with

the total capacitance split about 75/25% with the Aluminum

being the larger value.

The TO-220 can be attached to a typical heatsink, or se-

cured to a copper plane on a PC board. If a copper plane is

to be used, the values of θ_(JA)will be the same as shown in

the next section for the TO-263.

If two capacitors are paralleled, the effective ESR is the

parallel of the two individual values. The “flatter” ESR of the

Tantalum will keep the effective ESR from rising as quickly at

low temperatures.

If a manufactured heatsink is to be selected, the value of

heatsink-to-ambient thermal resistance, θ_(H−A), must first be

calculated:

θ_(H−A)= θ_(JA)− θ_(C−H)− θ_(J−C)

Where: θ_(J−C)is defined as the thermal resistance from the

junction to the surface of the case. A value of

3˚C/W can be assumed for θ_(J−C)for this

calculation.

HEATSINKING

A heatsink may be required depending on the maximum

power dissipation and maximum ambient temperature of the

application. Under all possible operating conditions, the junc-

tion temperature must be within the range specified under

Absolute Maximum Ratings.

θ_(C−H)is defined as the thermal resistance between

the case and the surface of the heatsink. The

value of θ_(C−H)will vary from about 1.5˚C/W to

about 2.5˚C/W (depending on method of at-

tachment, insulator, etc.). If the exact value is

unknown, 2˚C/W should be assumed for

To determine if a heatsink is required, the power dissipated

by the regulator, P_D, must be calculated.

The figure below shows the voltages and currents which are

present in the circuit, as well as the formula for calculating

the power dissipated in the regulator:

θ_(C−H)

When a value for θ_(H−A)is found using the equation shown,

a heatsink must be selected that has a value that is less than

or equal to this number.

θ_(H−A)is specified numerically by the heatsink manufacturer

in the catalog, or shown in a curve that plots temperature rise

vs power dissipation for the heatsink.

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.

00882237

= I ÷ I

L G

Figure 3 shows for the TO-263 the measured values of θ_(JA)

for different copper area sizes using a typical PCB with 1

ounce copper and no solder mask over the copper area used

for heatsinking.

= (V − V

) I + (V ) I

OUT L IN G

FIGURE 2. Power Dissipation Diagram

The next parameter which must be calculated is the maxi-

mum allowable temperature rise, T_R(max). This is calcu-

lated by using the formula:

T_R(max) = T_J(max) − T_A(max)

where: T_J(max) is the maximum allowable junction tem-

perature, which is 125˚C for commercial

grade parts.

T_A(max) is the maximum ambient temperature

which will be encountered in the

application.

Using the calculated values for T_R(max) and P_D, the maxi-

mum allowable value for the junction-to-ambient thermal

resistance, θ_(JA), can now be found:

θ_(JA)= T_R(max)/P_D

00882238

IMPORTANT: If the maximum allowable value for θ_(JA)is

found to be ≥ 53˚C/W for the TO-220 package, ≥ 80˚C/W for

the TO-263 package, or ≥174˚C/W for the SOT-223 pack-

age, no heatsink is needed since the package alone will

dissipate enough heat to satisfy these requirements.

FIGURE 3. θ_(JA)vs. Copper (1 ounce) Area for the

TO-263 Package

As shown in the figure, increasing the copper area beyond 1

square inch produces very little improvement. It should also

be observed that the minimum value of θ_(JA)for the TO-263

package mounted to a PCB is 32˚C/W.

If the calculated value for θ_(JA)falls below these limits, a

heatsink is required.

As a design aid, Figure 4 shows the maximum allowable

power dissipation compared to ambient temperature for the

TO-263 device (assuming θ_(JA)is 35˚C/W and the maximum

junction temperature is 125˚C).

www.national.com

Application Hints (Continued)

00882240

00882239

FIGURE 5. θ_(JA)vs. Copper (2 ounce) Area for the

SOT-223 Package

FIGURE 4. Maximum Power Dissipation vs. T_AMBfor

the TO-263 Package

Figure 5 and Figure 6 show the information for the SOT-223

package. Figure 6 assumes a θ_(JA)of 74˚C/W for 1 ounce

copper and 51˚C/W for 2 ounce copper and a maximum

junction temperature of 125˚C.

00882241

FIGURE 6. Maximum Power Dissipation vs. T_AMBfor the SOT-223 Package

www.national.com

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 MP04A

16 Lead Dual-in-Line Package (J)

Order Number LM2940J-5.0/883 (5962-8958701EA),

LM2940J-8.0/883 (5962-9088301QEA),

LM2940J-12/883 (5962-9088401QEA),

LM2940J-15/883 (5962-9088501QEA)

See NS Package Number J16A

www.national.com

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

16 Lead Surface Mount Package (WG)

Order Number LM2940WG5.0/883 (5962-8958701XA)

See NS Package Number WG16A

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

www.national.com

Physical Dimensions inches (millimeters) unless otherwise noted (Continued)

3-Lead TO-263 Surface Mount Package (MP)

Order Number LM2940S-5.0, LM2940S-8.0,

LM2940S-9.0, LM2940S-10, LM2940S-12,

LM2940CS-5.0, LM2940CS-12 or LM2940CS-15

NS Package Number TS3B

8-Lead LLP

Order Number LM2940LD-5.0, LM2940LD-8.0,

LM2940LD-9.0, LM2940LD-10,

LM2940LD-12 or LM2940LD-15

NS Package Number LDC08A

www.national.com

Notes

LIFE SUPPORT POLICY

NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT

DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant

into the body, or (b) support or sustain life, and

whose failure to perform when properly used in

accordance with instructions for use provided in the

labeling, can be reasonably expected to result in a

significant injury to the user.

2. A critical component is any component of a life

support device or system whose failure to perform

can be reasonably expected to cause the failure of

the life support device or system, or to affect its

safety or effectiveness.

National Semiconductor

Americas Customer

Support Center

National Semiconductor

Europe Customer Support Center

Fax: +49 (0) 180-530 85 86

National Semiconductor

Asia Pacific Customer

Support Center

National Semiconductor

Japan Customer Support Center

Fax: 81-3-5639-7507

Email: new.feedback@nsc.com

Tel: 1-800-272-9959

Email: europe.support@nsc.com

Deutsch Tel: +49 (0) 69 9508 6208

English Tel: +44 (0) 870 24 0 2171

Français Tel: +33 (0) 1 41 91 8790

Fax: 65-6250 4466

Email: ap.support@nsc.com

Tel: 65-6254 4466

Email: nsj.crc@jksmtp.nsc.com

Tel: 81-3-5639-7560

www.national.com

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.

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LM2940IMP-12产品参数

型号:	LM2940IMP-12
是否无铅：	不含铅
是否Rohs认证：	不符合
生命周期：	Active
IHS 制造商：	ROCHESTER ELECTRONICS LLC
零件包装代码：	SOT-223
包装说明：	SOT-223, 4 PIN
针数：	4
Reach Compliance Code：	unknown
风险等级：	5.68
Is Samacsys：	N
最大回动电压 1：	1 V
最大输入电压：	26 V
最小输入电压：	13.6 V
JESD-30 代码：	R-PDSO-G4
JESD-609代码：	e0
长度：	6.5 mm
湿度敏感等级：	1
功能数量：	1
端子数量：	4
工作温度TJ-Max：	85 °C
工作温度TJ-Min：	-40 °C
最大输出电流 1：	1 A
最大输出电压 1：	12.6 V
最小输出电压 1：	11.4 V
标称输出电压 1：	12 V
封装主体材料：	PLASTIC/EPOXY
封装代码：	SOP
封装形状：	RECTANGULAR
封装形式：	SMALL OUTLINE
峰值回流温度（摄氏度）：	260
调节器类型：	FIXED POSITIVE SINGLE OUTPUT LDO REGULATOR
座面最大高度：	1.8 mm
表面贴装：	YES
技术：	BIPOLAR
端子面层：	TIN LEAD
端子形式：	GULL WING
端子节距：	2.3 mm
端子位置：	DUAL
处于峰值回流温度下的最长时间：	40
宽度：	3.56 mm
Base Number Matches：	1

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