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LM7818CT

3-Terminal Positive Regulators

International Cmos Technology 

September 2001

LM340/LM78XX Series

3-Terminal Positive Regulators

General Description

The LM140/LM340A/LM340/LM7800C monolithic 3-terminal

positive voltage regulators employ internal current-limiting,

thermal shutdown and safe-area compensation, making

them essentially indestructible. If adequate heat sinking is

provided, they can deliver over 1.0A output current. They are

intended as fixed voltage regulators in a wide range of

applications including local (on-card) regulation for elimina-

tion of noise and distribution problems associated with

single-point regulation. In addition to use as fixed voltage

regulators, these devices can be used with external compo-

nents to obtain adjustable output voltages and currents.

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.

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

steel TO-3 power package. The LM340A/LM340/LM7800C

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.

Features

n Complete specifications at 1A load

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

over the temperature range (LM340A)

n Line regulation of 0.01% of VOUT/V of ∆VIN at 1A load

(LM340A)

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

n Internal thermal overload protection

n Internal short-circuit current limit

n Output transistor safe area protection

n P+ Product Enhancement tested

Device

Output

Voltages

Packages

LM140

5, 12, 15 TO-3 (K)

LM340A/LM340 5, 12, 15 TO-3 (K), TO-220 (T),

SOT-223 (MP), TO-263 (S)

(5V and 12V only)

LM7800C

5, 8, 12, TO-220 (T)

15

Typical Applications

Fixed Output Regulator

Adjustable Output Regulator

00778101

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

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

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

Current Regulator

00778102

VOUT = 5V + (5V/R1 + IQ) R2 5V/R1 > 3 IQ,

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

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

Packages

00778103

∆IQ = 1.3 mA over line and load changes.

Scale 1:1

00778138

© 2001 National Semiconductor Corporation DS007781

www.national.com

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