LM340T-15 [TI]

LM340/LM78XX Series 3-Terminal Positive Regulators; LM340 / LM78XX系列三端稳压器正


型号：	LM340T-15
厂家：	TEXAS INSTRUMENTS
描述：	LM340/LM78XX Series 3-Terminal Positive Regulators LM340 / LM78XX系列三端稳压器正三端稳压器
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中文：	中文翻译
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LM340

LM340/LM78XX Series 3-Terminal Positive Regulators

Literature Number: SNOSBT0H

July 2006

LM340/LM78XX Series

3-Terminal Positive Regulators

General Description

The 5V, 12V, and 15V regulator options are available in the

steel TO-3 power package. The LM340A/LM340/LM78XXC

series is available in the TO-220 plastic power package, and

the LM340-5.0 is available in the SOT-223 package, as well

as the LM340-5.0 and LM340-12 in the surface-mount TO-

263 package.

The

LM140/LM340A/LM340/LM78XXC

monolithic

3-terminal positive voltage regulators employ internal

current-limiting, thermal shutdown and safe-area compensa-

tion, making them essentially indestructible. If adequate heat

sinking is provided, they can deliver over 1.0A output cur-

rent. They are intended as fixed voltage regulators in a wide

range of applications including local (on-card) regulation for

elimination of noise and distribution problems associated

with single-point regulation. In addition to use as fixed volt-

age regulators, these devices can be used with external

components to obtain adjustable output voltages and cur-

rents.

Features

n Complete specifications at 1A load

n Output voltage tolerances of 2% at T_j= 25˚C and 4%

over the temperature range (LM340A)

n Line regulation of 0.01% of V_OUT/V of ∆V_INat 1A load

(LM340A)

n Load regulation of 0.3% of V_OUT/A (LM340A)

n Internal thermal overload protection

n Internal short-circuit current limit

n Output transistor safe area protection

n P⁺Product Enhancement tested

Considerable effort was expended to make the entire series

of regulators easy to use and minimize the number of exter-

nal components. It is not necessary to bypass the output,

although this does improve transient response. Input by-

passing is needed only if the regulator is located far from the

filter capacitor of the power supply.

Typical Applications

Fixed Output Regulator

Adjustable Output Regulator

00778101

*Required if the regulator is located far from the power supply filter.

00778102

= 5V + (5V/R1 + I ) R2 5V/R1 3 I ,

Q Q

OUT

**Although no output capacitor is needed for stability, it does help transient

response. (If needed, use 0.1 µF, ceramic disc).

load regulation (L ) ≈ [(R1 + R2)/R1] (L of LM340-5).

Comparison between SOT-223 and D-Pak (TO-252)

Packages

Current Regulator

00778103

00778138

Scale 1:1

∆I = 1.3 mA over line and load changes.

DS007781

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Ordering Information

Package

Temperature

Range

Part Number

Packaging Marking

Transport Media

NSC

Drawing

K02A

3-Lead TO-3

-55˚C to +125˚C

LM140K-5.0

LM140K-12

LM140K 5.0P+

LM140K 12P+

50 Per Tray

LM140K-15

LM140K 15P+

50 Per Tray

0˚C to +125˚C

LM340K-5.0

LM340K 5.0 7805P+

LM340K 12 7812P+

LM340K 15 7815P+

LM340AT 5.0 P+

LM340T5 7805 P+

LM340T12 7812 P+

LM340T15 7815 P+

LM7808CT

50 Per Tray

LM340K-12

50 Per Tray

LM340K-15

50 Per Tray

3-lead TO-220

3-Lead TO-263

LM340AT-5.0

LM340T-5.0

45 Units/Rail

T03B

TS3B

45 Units/Rail

LM340T-12

45 Units/Rail

LM340T-15

45 Units/Rail

LM7808CT

45 Units/Rail

0˚C to +125˚C

LM340S-5.0

45 Units/Rail

LM340S-5.0 P+

LM340S-12 P+

LM340AS-5.0 P+

N00A

LM340SX-5.0

LM340S-12

500 Units Tape and Reel

45 Units/Rail

LM340SX-12

LM340AS-5.0

LM340ASX-5.0

LM340MP-5.0

LM340MPX-5.0

LM140KG-5 MD8

LM140KG-12 MD8

LM140KG-15 MD8

LM340-5.0 MDA

LM7808C MDC

500 Units Tape and Reel

45 Units/Rail

500 Units Tape and Reel

1k Units Tape and Reel

2k Units Tape and Reel

Waffle Pack or Gel Pack

4-Lead

0˚C to +125˚C

−55˚C to 125˚C

MP04A

SOT-223

Unpackaged

Die

DL069089

DL059093

DI074056

0˚C to +125˚C

Connection Diagrams

TO-3 Metal Can Package (K)

TO-220 Power Package (T)

00778112

00778111

Top View

See Package Number T03B

Bottom View

See Package Number K02A

TO-263 Surface-Mount Package (S)

3-Lead SOT-223

00778120

Top View

00778143

Top View

See Package Number TS3B

See Package Number MP04A

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

TO-220 Package (T), TO-263

Package (S)

230˚C

2 kV

ESD Susceptibility (Note 3)

(Note 5)

Operating Conditions (Note 1)

Temperature Range (T_A) (Note 2)

DC Input Voltage

35V

Internally Limited

150˚C

Internal Power Dissipation (Note 2)

Maximum Junction Temperature

Storage Temperature Range

Lead Temperature (Soldering, 10 sec.)

TO-3 Package (K)

LM140

−55˚C to +125˚C

0˚C to +125˚C

LM340A, LM340

LM7808C

−65˚C to +150˚C

300˚C

LM340A Electrical Characteristics

I_OUT= 1A, 0˚C ≤ T_J≤ + 125˚C (LM340A) unless otherwise specified (Note 4)

Output Voltage

12V

19V

15V

Symbol

V_O

Input Voltage (unless otherwise noted)

10V

23V

Units

Parameter

Output Voltage

Conditions

Min Typ Max Min Typ Max Min Typ Max

T_J= 25˚C

4.9

4.8

5.1 11.75 12 12.25 14.7 15 15.3

5.2 11.5 12.5 14.4 15.6

P_D≤ 15W, 5 mA ≤ I_O≤ 1A

V_MIN≤ V_IN≤ V_MAX

(7.5 ≤ V_IN≤ 20) (14.8 ≤ V_IN≤ 27) (17.9 ≤ V_IN≤ 30)

10 18 22

(7.5 ≤ V_IN≤ 20) (14.8 ≤ V_IN≤ 27) (17.9 ≤ V_IN≤ 30)

10 18 22

(7.5 ≤ V_IN≤ 20) (14.5 ≤ V_IN≤ 27) (17.5 ≤ V_IN≤ 30)

∆V_O

Line Regulation I_O= 500 mA

∆V_IN

T_J= 25˚C

∆V_IN

T_J= 25˚C

Over Temperature

∆V_IN

(8 ≤ V_IN≤ 12)

(16 ≤ V_IN≤ 22)

(20 ≤ V_IN≤ 26)

∆V_O

Load Regulation T_J= 25˚C

5 mA ≤ I_O≤ 1.5A

250 mA ≤ I_O≤ 750

Over Temperature,

5 mA ≤ I_O≤ 1A

I_Q

Quiescent

Current

T_J= 25˚C

Over Temperature

6.5

∆I_Q

Quiescent

Current

5 mA ≤ I_O≤ 1A

0.5

Change

T_J= 25˚C, I_O= 1A

V_MIN≤ V_IN≤ V_MAX

I_O= 500 mA

0.8

(7.5 ≤ V_IN≤ 20) (14.8 ≤ V_IN≤ 27) (17.9 ≤ V_IN≤ 30)

0.8

(8 ≤ V_IN≤ 25)

0.8

V_MIN≤ V_IN≤ V_MAX

T_A= 25˚C, 10 Hz ≤ f ≤ 100 kHz

(15 ≤ V_IN≤ 30) (17.9 ≤ V_IN≤ 30)

V_N

Output Noise

Voltage

µV

Ripple Rejection T_J= 25˚C, f = 120 Hz, I_O= 1A

or f = 120 Hz, I_O= 500 mA,

Over Temperature,

V_MIN≤ V_IN≤ V_MAX

(8 ≤ V_IN≤ 18)

(15 ≤ V_IN≤ 25)

(18.5 ≤ V_IN

28.5)

2.0

≤

R_O

Dropout Voltage T_J= 25˚C, I_O= 1A

2.0

Output

f = 1 kHz

mΩ

Resistance

Short-Circuit

Current

T_J= 25˚C

2.1

1.5

1.2

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LM340A Electrical Characteristics (Continued)

I_OUT= 1A, 0˚C ≤ T_J≤ + 125˚C (LM340A) unless otherwise specified (Note 4)

Output Voltage

12V

19V

15V

23V

Symbol

Input Voltage (unless otherwise noted)

10V

Units

Parameter

Conditions

Min Typ Max Min Typ Max Min Typ Max

Peak Output

Current

T_J= 25˚C

2.4

Average TC of

V_O

Min, T_J= 0˚C, I_O= 5 mA

T_J= 25˚C

−0.6

−1.5

−1.8

mV/˚C

V_IN

Input Voltage

Required to

Maintain

7.5

14.5

17.5

Line Regulation

LM140 Electrical Characteristics (Note 4)

−55˚C ≤ T_J≤ +150˚C unless otherwise specified

Output Voltage

10V

12V

19V

15V

23V

Symbol

V_O

Input Voltage (unless otherwise noted)

Units

Parameter

Conditions

T_J= 25˚C, 5 mA ≤ I_O≤ 1A

P_D≤ 15W, 5 mA ≤ I_O≤ 1A

V_MIN≤ V_IN≤ V_MAX

Min Typ Max Min Typ Max Min Typ Max

Output Voltage

4.8

5.2 11.5

5.25 11.4

12 12.5 14.4 15 15.6

12.614.25 15.75

(18.5 ≤ V_IN

4.75

(8 ≤ V_IN≤ 20)

(15.5 ≤ V_IN≤ 27)

≤

30)

∆V_O

Line Regulation

I_O= 500 mA T_J= 25˚C

120

150 mV

∆V_IN

(7 ≤ V_IN≤ 25)

(14.5 ≤ V_IN≤ 30)

(17.5 ≤ V_IN

≤

30)

−55˚C ≤ T_J≤ +150˚C

120

150 mV

∆V_IN

(8 ≤ V_IN≤ 20)

(15 ≤ V_IN≤ 27)

(18.5 ≤ V_IN

≤

30)

I_O≤ 1A

T_J= 25˚C

120

150 mV

∆V_IN

(7.5 ≤ V_IN≤ 20) (14.6 ≤ V_IN≤ 27)

(17.7 ≤ V_IN

≤

30)

−55˚C ≤ T_J≤ +150˚C

∆V_IN

(16 ≤ V_IN≤ 22)

75 mV

(20 ≤ V_IN≤ 26)

(8 ≤ V_IN≤ 12)

∆V_O

Load Regulation

T_J= 25˚C

5 mA ≤ I_O≤ 1.5A

250 mA ≤ I_P≤ 750

12 120

12 150 mV

75 mV

−55˚C ≤ T_J≤ +150˚C,

5 mA ≤ I_O≤ 1A

120

150 mV

I_Q

Quiescent Current I_O≤ 1A

T_J= 25˚C

−55˚C ≤ T_J≤ +150˚C

∆I_Q

Quiescent Current 5 mA ≤ I_O≤ 1A

0.5

Change

T_J= 25˚C, I_O≤ 1A

0.8

(15 ≤ V_IN≤ 27)

0.8 mA

V_MIN≤ V_IN≤ V_MAX

(8 ≤ V_IN≤ 20)

(18.5 ≤ V_IN

≤

30)

I_O= 500 mA, −55˚C ≤ T_J≤ +150˚C

V_MIN≤ V_IN≤ V_MAX

0.8

(15 ≤ V_IN≤ 30)

0.8 mA

(8 ≤ V_IN≤ 25)

(18.5 ≤ V_IN

≤

30)

V_N

Output Noise

Voltage

T_A= 25˚C, 10 Hz ≤ f ≤ 100 kHz

µV

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LM140 Electrical Characteristics (Note 4) (Continued)

−55˚C ≤ T_J≤ +150˚C unless otherwise specified

Output Voltage

10V

12V

19V

15V

23V

Symbol

Input Voltage (unless otherwise noted)

Units

Parameter

Conditions

Min Typ Max Min Typ Max Min Typ Max

Ripple Rejection

I_O≤ 1A, T_J= 25˚C

68 80

60 70

f = 120 Hz

I_O≤ 500 mA,

−55˚C ≤ T_J≤+150˚C

V_MIN≤ V_IN≤ V_MAX

(8 ≤ V_IN≤ 18)

(15 ≤ V_IN≤ 25)

(18.5 ≤ V_IN

28.5)

2.0

≤

R_O

Dropout Voltage

T_J= 25˚C, I_O= 1A

2.0

mΩ

Output Resistance f = 1 kHz

Short-Circuit

Current

T_J= 25˚C

2.1

1.5

1.2

Peak Output

Current

T_J= 25˚C

2.4

Average TC of

V_OUT

0˚C ≤ T_J≤ +150˚C, I_O= 5 mA

T_J= 25˚C, I_O≤ 1A

−0.6

−1.5

−1.8

mV/˚C

V_IN

Input Voltage

Required to

Maintain

7.5

14.6

17.7

Line Regulation

LM340 Electrical Characteristics (Note 4)

0˚C ≤ T_J≤ +125˚C unless otherwise specified

Output Voltage

12V

19V

15V

23V

Symbol

V_O

Input Voltage (unless otherwise noted)

10V

Units

Parameter

Conditions

T_J= 25˚C, 5 mA ≤ I_O≤ 1A

P_D≤ 15W, 5 mA ≤ I_O≤ 1A

V_MIN≤ V_IN≤ V_MAX

Min Typ Max Min Typ Max Min Typ Max

Output Voltage

4.8

5.2 11.5 12 12.5 14.4 15 15.6

5.25 11.4 12.6 14.25 15.75

(17.5 ≤ V_IN≤ 30)

4.75

(7.5 ≤ V_IN≤ 20)

(14.5 ≤ V_IN≤

27)

∆V_O

Line Regulation

I_O= 500 mA T_J= 25˚C

120

150 mV

∆V_IN

(7 ≤ V_IN≤ 25)

(14.5 ≤ V_IN

≤

(17.5 ≤ V_IN≤ 30)

30)

0˚C ≤ T_J≤ +125˚C

(8 ≤ V_IN≤ 20)

120

(15 ≤ V_IN≤ 27) (18.5 ≤ V_IN≤ 30)

120 150 mV

150 mV

∆V_IN

I_O≤ 1A

T_J= 25˚C

∆V_IN

(7.5 ≤ V_IN≤ 20)

(14.6 ≤ V_IN

27)

≤

(17.7 ≤ V_IN≤ 30)

0˚C ≤ T_J≤ +125˚C

∆V_IN

(8 ≤ V_IN≤ 12)

(16 ≤ V_IN≤ 22) (20 ≤ V_IN≤ 26)

∆V_O

Load Regulation

T_J= 25˚C

5 mA ≤ I_O≤ 1.5A

250 mA ≤ I_O≤ 750 mA

12 120

12 150 mV

75 mV

150 mV

5 mA ≤ I_O≤ 1A, 0˚C ≤ T_J≤

120

+125˚C

I_Q

Quiescent Current

I_O≤ 1A

T_J= 25˚C

0˚C ≤ T_J≤ +125˚C

8.5

∆I_Q

Quiescent Current

Change

5 mA ≤ I_O≤ 1A

0.5

T_J= 25˚C, I_O≤ 1A

1.0

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LM340 Electrical Characteristics (Note 4) (Continued)

0˚C ≤ T_J≤ +125˚C unless otherwise specified

Output Voltage

10V

12V

19V

15V

23V

Symbol

Input Voltage (unless otherwise noted)

Units

Parameter

Conditions

V_MIN≤ V_IN≤ V_MAX

Min Typ Max Min Typ Max Min Typ Max

(7.5 ≤ V_IN≤ 20)

(14.8 ≤ V_IN

≤

(17.9 ≤ V_IN≤ 30)

27)

I_O≤ 500 mA, 0˚C ≤ T_J≤ +125˚C

V_MIN≤ V_IN≤ V_MAX

1.0

(7 ≤ V_IN≤ 25)

(14.5 ≤ V_IN

≤

(17.5 ≤ V_IN≤ 30)

30)

V_N

Output Noise

Voltage

T_A= 25˚C, 10 Hz ≤ f ≤ 100 kHz

µV

Ripple Rejection

I_O≤ 1A, T_J=

25˚C

f = 120 Hz

or I_O≤ 500 mA,

0˚C ≤ T_J≤ +125˚C

V_MIN≤ V_IN≤ V_MAX

(8 ≤ V_IN≤ 18)

(15 ≤ V_IN≤ 25)

(18.5 ≤ V_IN

28.5)

2.0

≤

R_O

Dropout Voltage

T_J= 25˚C, I_O= 1A

f = 1 kHz

2.0

mΩ

Output Resistance

Short-Circuit Current T_J= 25˚C

2.1

2.4

1.5

2.4

1.2

Peak Output

Current

T_J= 25˚C

2.4

Average TC of V_OUT0˚C ≤ T_J≤ +125˚C, I_O= 5 mA

−0.6

7.5

−1.5

14.6

−1.8

mV/˚C

V_IN

Input Voltage

Required to

Maintain

T_J= 25˚C, I_O≤ 1A

17.7

Line Regulation

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 at any ambient temperature is a function of the maximum junction temperature for operation (T

= 125˚C or

JMAX

150˚C), the junction-to-ambient thermal resistance (θ ), and the ambient temperature (T ). P

= (T − T )/θ . If this dissipation is exceeded, the die

JMAX A JA

DMAX

temperature will rise above T

and the electrical specifications do not apply. If the die temperature rises above 150˚C, the device will go into thermal shutdown.

JMAX

For the TO-3 package (K, KC), the junction-to-ambient thermal resistance (θ ) is 39˚C/W. When using a heatsink, θ is the sum of the 4˚C/W junction-to-case

thermal resistance (θ ) of the TO-3 package and the case-to-ambient thermal resistance of the heatsink. For the TO-220 package (T), θ is 54˚C/W and θ is

4˚C/W. If SOT-223 is used, the junction-to-ambient thermal resistance is 174˚C/W and can be reduced by a heatsink (see Applications Hints on heatsinking).

If the TO-263 package is used, the thermal resistance can be reduced by increasing the PC board copper area thermally connected to the package: Using 0.5 square

inches of copper area, θ is 50˚C/W; with 1 square inch of copper area, θ is 37˚C/W; and with 1.6 or more inches of copper area, θ is 32˚C/W.

Note 3: ESD rating is based on the human body model, 100 pF discharged through 1.5 kΩ.

Note 4: All characteristics are measured with a 0.22 µF capacitor from input to ground and a 0.1 µF capacitor from output to ground. All characteristics except noise

voltage and ripple rejection ratio are measured using pulse techniques (t ≤ 10 ms, duty cycle ≤ 5%). Output voltage changes due to changes in internal temperature

must be taken into account separately.

Note 5: Military datasheets are available upon request. At the time of printing, the military datasheet specifications for the LM140K-5.0/883, LM140K-12/883, and

LM140K-15/883 complied with the min and max limits for the respective versions of the LM140. The LM140H and LM140K may also be procured as JAN devices

on slash sheet JM38510/107.

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LM7808C

Electrical Characteristics

0˚C ≤ T_J≤ +150˚C, V_I= 14V, I_O= 500 mA, C_I= 0.33 µF, C_O= 0.1 µF, unless otherwise specified

Symbol

Parameter

Conditions (Note 6)

LM7808C

Typ

8.0

Units

Min

Max

8.3

160

V_O

Output Voltage

T_J= 25˚C

7.7

∆V_O

Line Regulation

Load Regulation

10.5V ≤ V_I≤ 25V

6.0

11.0V ≤ V_I≤ 17V

5.0 mA ≤ I_O≤ 1.5A

250 mA ≤ I_O≤ 750

2.0

∆V_O

T_J= 25˚C

160

4.0

V_O

I_Q

Output Voltage

Quiescent Current

Quiescent

11.5V ≤ V_I≤ 23V, 5.0 mA ≤ I_O≤ 1.0A, P ≤ 15W

T_J= 25˚C

7.6

8.4

8.0

1.0

0.5

4.3

∆I_Q

With Line

With Load

11.5V ≤ V_I≤ 25V

Current Change

Noise

5.0 mA ≤ I_O≤ 1.0A

V_N

T_A= 25˚C, 10 Hz ≤ f ≤ 100 kHz

f = 120 Hz, I_O= 350 mA, T_J= 25˚C

I_O= 1.0A, T_J= 25˚C

f = 1.0 kHz

µV

∆V_I/∆V_ORipple Rejection

V_DO

R_O

Dropout Voltage

2.0

Output Resistance

mΩ

I_OS

Output Short Circuit Current

Peak Output Current

T_J= 25˚C, V_I= 35V

T_J= 25˚C

0.45

2.2

0.8

I_PK

∆V_O/∆T

Average Temperature

I_O= 5.0 mA

mV/˚C

Coefficient of Output Voltage

Note 6: All characteristics are measured with a 0.22 µF capacitor from input to ground and a 0.1 µF capacitor from output to ground. All characteristics except noise

voltage and ripple rejection ratio are measured using pulse techniques (t ≤ 10 ms, duty cycle ≤ 5%). Output voltage changes due to changes in internal temperature

must be taken into account separately.

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Typical Performance Characteristics

Maximum Average Power Dissipation

00778122

00778123

Maximum Power Dissipation (TO-263)

(See Note 2)

Output Voltage (Normalized to 1V at T_J= 25˚C)

00778124

00778125

Note: Shaded area refers to LM340A/LM340, LM7805C, LM7812C and

LM7815C.

Ripple Rejection

00778126

00778127

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Typical Performance Characteristics (Continued)

Output Impedance

Dropout Characteristics

00778129

00778128

Quiescent Current

Peak Output Current

00778131

00778130

Note: Shaded area refers to LM340A/LM340, LM7805C, LM7812C and

LM7815C.

Dropout Voltage

Quiescent Current

00778132

Note: Shaded area refers to LM340A/LM340, LM7805C, LM7812C and

LM7815C.

00778133

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Line Regulation

140AK-5.0, I_OUT= 1A, T_A= 25˚C

140AK-5.0, V_IN= 10V, T_A= 25˚C

00778106

00778105

Equivalent Schematic

00778107

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Application Hints

The LM340/LM78XX series is designed with thermal protec-

tion, output short-circuit protection and output transistor safe

area protection. However, as with any IC regulator, it be-

comes necessary to take precautions to assure that the

regulator is not inadvertently damaged. The following de-

scribes possible misapplications and methods to prevent

damage to the regulator.

SHORTING THE REGULATOR INPUT

When using large capacitors at the output of these regula-

tors, a protection diode connected input to output (Figure 1)

may be required if the input is shorted to ground. Without the

protection diode, an input short will cause the input to rapidly

approach ground potential, while the output remains near

the initial V_OUTbecause of the stored charge in the large

output capacitor. The capacitor will then discharge through a

large internal input to output diode and parasitic transistors.

If the energy released by the capacitor is large enough, this

diode, low current metal and the regulator will be destroyed.

The fast diode in Figure 1 will shunt most of the capacitors

discharge current around the regulator. Generally no protec-

tion diode is required for values of output capacitance ≤ 10

µF.

00778108

FIGURE 1. Input Short

RAISING THE OUTPUT VOLTAGE ABOVE THE INPUT

VOLTAGE

Since the output of the device does not sink current, forcing

the output high can cause damage to internal low current

paths in a manner similar to that just described in the “Short-

ing the Regulator Input” section.

00778109

FIGURE 2. Regulator Floating Ground

REGULATOR FLOATING GROUND (Figure 2)

When the ground pin alone becomes disconnected, the

output approaches the unregulated input, causing possible

damage to other circuits connected to V_OUT. If ground is

reconnected with power “ON”, damage may also occur to the

regulator. This fault is most likely to occur when plugging in

regulators or modules with on card regulators into powered

up sockets. Power should be turned off first, thermal limit

ceases operating, or ground should be connected first if

power must be left on.

TRANSIENT VOLTAGES

If transients exceed the maximum rated input voltage of the

device, or reach more than 0.8V below ground and have

sufficient energy, they will damage the regulator. The solu-

tion is to use a large input capacitor, a series input break-

down diode, a choke, a transient suppressor or a combina-

tion of these.

00778110

FIGURE 3. Transients

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 this catalog, or shown in a curve that plots temperature

rise vs power dissipation for the heatsink.

www.national.com

Application Hints (Continued)

HEATSINKING TO-263 AND SOT-223 PACKAGE PARTS

Figures 6, 7 show the information for the SOT-223 package.

Figure 6 assumes a θ_(J–A)of 74˚C/W for 1 ounce copper and

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

perature of 125˚C.

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 plane.

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.

00778141

FIGURE 6. θ_(J–A)vs Copper (2 ounce) Area

for the SOT-223 Package

00778139

FIGURE 4. θ_(J–A)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_(J–A)for the TO-263

package mounted to a PCB is 32˚C/W.

As a design aid, Figure 5 shows the maximum allowable

power dissipation compared to ambient temperature for the

TO-263 device (assuming θ_(J–A)is 35˚C/W and the maxi-

mum junction temperature is 125˚C).

00778142

FIGURE 7. Maximum Power Dissipation vs

T_AMBfor the SOT-223 Package

Please see AN-1028 for power enhancement techniques to

be used with the SOT-223 package.

00778140

FIGURE 5. Maximum Power Dissipation vs

T_AMBfor the TO-263 Package

www.national.com

Typical Applications

Fixed Output Regulator

00778113

Note: Bypass capacitors are recommended for optimum stability and transient response, and should be located as close as possible to the regulator.

High Input Voltage Circuits

00778114

00778115

High Current Voltage Regulator

00778116

www.national.com

Typical Applications (Continued)

High Output Current, Short Circuit Protected

00778117

Positive and Negative Regulator

00778118

www.national.com

Physical Dimensions inches (millimeters) unless otherwise noted

TO-3 Metal Can Package (K)

NS Package Number K02A

TO-263 Surface-Mount Package (S)

NS Package Number TS3B

www.national.com

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

TO-220 Power Package (T)

NS Package Number T03B

3-Lead SOT-223 Package

NS Package Number MP04A

www.national.com

Notes

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.

For the most current product information visit us at www.national.com.

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provided in the labeling, can be reasonably expected to result

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2. A critical component is any component of a life support

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www.national.com

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LM340T-15 [TI]

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