LM140/LM340A/LM340/LM7800C Series 3-Terminal Positive Regulators
May 1999
LM140/LM340A/LM340/LM7800C
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 appli-
cations including local (on-card) regulation for elimination 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 components to ob-
tain 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, al-
though this does improve transient response. Input bypass-
ing 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 T
j
= 25˚C and
±
4%
over the temperature range (LM140A/LM340A)
n
Line regulation of 0.01% of V
OUT
/V of
∆V
IN
at 1A load
(LM140A/LM340A)
n
Load regulation of 0.3% of V
OUT
/A (LM140A/LM340A)
n
Internal thermal overload protection
n
Internal short-circuit current limit
n
Output transistor safe area protection
n
P
+
Product Enhancement tested
Device
LM140
LM340A/LM340
Output
Voltages
5, 12,
15
5, 12,
15
5, 8, 12,
15
TO-3 (K)
TO-3 (K), TO-220 (T),
SOT-223 (MP), TO-263 (S)
(5V and 12V only)
TO-220 (T)
Packages
LM7800C
Typical Applications
Fixed Output Regulator
Adjustable Output Regulator
DS007781-1
*
Required if the regulator is located far from the power supply filter.
**
Although no output capacitor is needed for stability, it does help transient
DS007781-2
response. (If needed, use 0.1 µF, ceramic disc).
V
OUT
= 5V + (5V/R1 + I
Q
) R2 5V/R1
>
3 I
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
DS007781-3
∆I
Q
= 1.3 mA over line and load changes.
DS007781-38
Scale 1:1
© 1999 National Semiconductor Corporation
DS007781
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
