LM340/LM78XX Series
3-Terminal Positive Regulators
General Description
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.
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/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.
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
IN
at 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
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).
00778102
V
OUT
= 5V + (5V/R1 + I
Q
) R2 5V/R1
>
3I
Q
,
load regulation (L
r
) ≈ [(R1 + R2)/R1] (L
r
of LM340-5).
Current Regulator
Comparison between SOT-223 and D-Pak (TO-252)
Packages
00778103
∆I
Q
= 1.3 mA over line and load changes.
00778138
Scale 1:1
July 2006
LM340/LM78XX Series 3-Terminal Positive Regulators
© 2006 National Semiconductor Corporation DS007781 www.national.com
