Series 3-Terminal Positive Regulators
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
n Complete specifications at 1A load
n Output voltage tolerances of ±2% at Tj = 25˚C and ±4%
over the temperature range (LM140A/LM340A)
n Line regulation of 0.01% of VOUT/V of ∆VIN at 1A load
n Load regulation of 0.3% of VOUT/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
LM340A/LM340 5, 12,
5, 8, 12,
TO-3 (K), TO-220 (T),
SOT-223 (MP), TO-263 (S)
(5V and 12V only)
Fixed Output Regulator
Adjustable Output Regulator
*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).
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)
∆IQ = 1.3 mA over line and load changes.
© 1999 National Semiconductor Corporation DS007781