LM341/LM78MXX Series
3-Terminal Positive Voltage Regulators
General Description
The LM341 and LM78MXX series of three-terminal positive
voltage regulators employ built-in current limiting, thermal
shutdown, and safe-operating area protection which makes
them virtually immune to damage from output overloads.
With adequate heatsinking, they can deliver in excess of
0.5A output current. Typical applications would include local
(on-card) regulators which can eliminate the noise and de-
graded performance associated with single-point regulation.
Features
nOutput current in excess of 0.5A
nNo external components
nInternal thermal overload protection
nInternal short circuit current-limiting
nOutput transistor safe-area compensation
nAvailable in TO-220, TO-39, and TO-252 D-PAK
packages
nOutput voltages of 5V, 12V, and 15V
Connection Diagrams
TO-39 Metal Can Package (H)
01048405
Bottom View
Order Number LM78M05CH, LM78M12CH or LM78M15CH
See NS Package Number H03A
TO-220 Power Package (T)
01048406
Top View
Order Number LM341T-5.0, LM341T-12, LM341T-15, LM78M05CT, LM78M12CT or LM78M15CT
See NS Package Number T03B
TO-252
01048419
Top View
Order Number LM78M05CDT
See NS Package Number TD03B
August 2005
LM341/LM78MXX Series 3-Terminal Positive Voltage Regulators
© 2005 National Semiconductor Corporation DS010484 www.national.com
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Lead Temperature (Soldering, 10 seconds)
TO-39 Package (H) 300˚C
TO-220 Package (T) 260˚C
Storage Temperature Range −65˚C to +150˚C
Operating Junction Temperature
Range −40˚C to +125˚C
Power Dissipation (Note 2) Internally Limited
Input Voltage
5V ≤V
O
≤15V 35V
ESD Susceptibility TBD
Electrical Characteristics
Limits in standard typeface are for T
J
= 25˚C, and limits in boldface type apply over the −40˚C to +125˚C operating temperature
range. Limits are guaranteed by production testing or correlation techniques using standard Statistical Quality Control (SQC)
methods.
LM341-5.0, LM78M05C
Unless otherwise specified: V
IN
= 10V, C
IN
= 0.33 µF, C
O
= 0.1 µF
Symbol Parameter Conditions Min Typ Max Units
V
O
Output Voltage I
L
= 500 mA 4.8 5.0 5.2 V
5mA≤I
L
≤500 mA 4.75 5.0 5.25
P
D
≤7.5W, 7.5V ≤V
IN
≤20V
V
R LINE
Line Regulation 7.2V ≤V
IN
≤25V I
L
= 100 mA 50 mV
I
L
= 500 mA 100
V
R LOAD
Load Regulation 5 mA ≤I
L
≤500 mA 100
I
Q
Quiescent Current I
L
= 500 mA 4 10.0 mA
∆I
Q
Quiescent Current Change 5 mA ≤I
L
≤500 mA 0.5
7.5V ≤V
IN
≤25V, I
L
= 500 mA 1.0
V
n
Output Noise Voltage f = 10 Hz to 100 kHz 40 µV
Ripple Rejection f = 120 Hz, I
L
= 500 mA
78 dB
V
IN
Input Voltage Required I
L
= 500 mA 7.2 V
to Maintain Line Regulation
∆V
O
Long Term Stability I
L
= 500 mA 20 mV/khrs
LM341/LM78MXX Series
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Electrical Characteristics
Limits in standard typeface are for T
J
= 25˚C, and limits in boldface type apply over the −40˚C to +125˚C operating temperature
range. Limits are guaranteed by production testing or correlation techniques using standard Statistical Quality Control (SQC)
methods. (Continued)
LM341-12, LM78M12C
Unless otherwise specified: V
IN
= 19V, C
IN
= 0.33 µF, C
O
= 0.1 µF
Symbol Parameter Conditions Min Typ Max Units
V
O
Output Voltage I
L
= 500 mA 11.5 12 12.5 V
5mA≤I
L
≤500 mA 11.4 12 12.6
P
D
≤7.5W, 14.8V ≤V
IN
≤27V
V
R LINE
Line Regulation 14.5V ≤V
IN
≤30V I
L
= 100 mA 120 mV
I
L
= 500 mA 240
V
R LOAD
Load Regulation 5 mA ≤I
L
≤500 mA 240
I
Q
Quiescent Current I
L
= 500 mA 4 10.0 mA
∆I
Q
Quiescent Current Change 5 mA ≤I
L
≤500 mA 0.5
14.8V ≤V
IN
≤30V, I
L
= 500 mA 1.0
V
n
Output Noise Voltage f = 10 Hz to 100 kHz 75 µV
Ripple Rejection f = 120 Hz, I
L
= 500 mA
71 dB
V
IN
Input Voltage Required I
L
= 500 mA 14.5 V
to Maintain Line Regulation
∆V
O
Long Term Stability I
L
= 500 mA 48 mV/khrs
LM341-15, LM78M15C
Unless otherwise specified: V
IN
= 23V, C
IN
= 0.33 µF, C
O
= 0.1 µF
Symbol Parameter Conditions Min Typ Max Units
V
O
Output Voltage I
L
= 500 mA 14.4 15 15.6 V
5mA≤I
L
≤500 mA 14.25 15 15.75
P
D
≤7.5W, 18V ≤V
IN
≤30V
V
R LINE
Line Regulation 17.6V ≤V
IN
≤30V I
L
= 100 mA 150 mV
I
L
= 500 mA 300
V
R LOAD
Load Regulation 5 mA ≤I
L
≤500 mA 300
I
Q
Quiescent Current I
L
= 500 mA 4 10.0 mA
∆I
Q
Quiescent Current Change 5 mA ≤I
L
≤500 mA 0.5
18V ≤V
IN
≤30V, I
L
= 500 mA 1.0
V
n
Output Noise Voltage f = 10 Hz to 100 kHz 90 µV
Ripple Rejection f = 120 Hz, I
L
= 500 mA
69 dB
V
IN
Input Voltage Required I
L
= 500 mA 17.6 V
to Maintain Line Regulation
∆V
O
Long Term Stability I
L
= 500 mA 60 mV/khrs
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the
device outside of its rated operating conditions.
Note 2: The typical thermal resistance of the three package types is:
T(TO-220) package: θ(JA) = 60 ˚C/W, θ(JC) = 5 ˚C/W
H(TO-39) package: θ(JA) = 120 ˚C/W, θ(JC) = 18 ˚C/W
DT (TO-252) package: θ(JA) = 92 ˚C/W, θ(JC) = 10 ˚C/W
LM341/LM78MXX Series
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Schematic Diagram
01048401
LM341/LM78MXX Series
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Typical Performance Characteristics
Peak Output Current Ripple Rejection
01048410 01048411
Ripple Rejection Dropout Voltage
01048412 01048413
Output Voltage (Normalized
to 1V at T
J
= 25˚C) Quiescent Current
01048414 01048415
LM341/LM78MXX Series
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Typical Performance Characteristics (Continued)
Quiescent Current Output Impedance
01048416 01048417
Line Transient Response Load Transient Response
01048407 01048408
Design Considerations
The LM78MXX/LM341XX fixed voltage regulator series has
built-in thermal overload protection which prevents the de-
vice from being damaged due to excessive junction tem-
perature.
The regulators also contain internal short-circuit protection
which limits the maximum output current, and safe-area
protection for the pass transistor which reduces the short-
circuit current as the voltage across the pass transistor is
increased.
Although the internal power dissipation is automatically lim-
ited, the maximum junction temperature of the device must
be kept below +125˚C in order to meet data sheet specifica-
tions. An adequate heatsink should be provided to assure
this limit is not exceeded under worst-case operating condi-
tions (maximum input voltage and load current) if reliable
performance is to be obtained).
1.0 HEATSINK CONSIDERATIONS
When an integrated circuit operates with appreciable cur-
rent, its junction temperature is elevated. It is important to
quantify its thermal limits in order to achieve acceptable
performance and reliability. This limit is determined by sum-
ming the individual parts consisting of a series of tempera-
ture rises from the semiconductor junction to the operating
environment. A one-dimension steady-state model of con-
duction heat transfer is demonstrated in The heat generated
at the device junction flows through the die to the die attach
pad, through the lead frame to the surrounding case mate-
rial, to the printed circuit board, and eventually to the ambi-
ent environment. Below is a list of variables that may affect
the thermal resistance and in turn the need for a heatsink.
R
θJC
(Component
Variables)
R
θCA
(Application
Variables)
Leadframe Size & Material Mounting Pad Size,
Material, & Location
No. of Conduction Pins Placement of Mounting Pad
Die Size PCB Size & Material
Die Attach Material Traces Length & Width
Molding Compound Size
and Material
Adjacent Heat Sources
Volume of Air
Air Flow
Ambient Temperature
Shape of Mounting Pad
LM341/LM78MXX Series
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Application Information The LM78MXX/LM341XX regulators have internal thermal
shutdown to protect the device from over-heating. Under all
possible operating conditions, the junction temperature of
the LM78MXX/LM341XX must be within the range of 0˚C to
125˚C. A heatsink may be required depending on the maxi-
mum power dissipation and maximum ambient temperature
of the application. To determine if a heatsink is needed, the
power dissipated by the regulator, P
D
, must be calculated:
I
IN
=I
L
+I
G
P
D
=(V
IN
−V
OUT
)I
L
+V
IN
I
G
shows the voltages and currents which are present in the
circuit.
The next parameter which must be calculated is the maxi-
mum allowable temperature rise, T
R
(max):
θ
JA
= TR (max)/P
D
If the maximum allowable value for θ
JA
˚C/w is found to be
≥60˚C/W for TO-220 package or ≥92˚C/W for TO-252 pack-
age, no heatsink is needed since the package alone will
dissipate enough heat to satisfy these requirements. If the
calculated value for θ
JA
fall below these limits, a heatsink is
required.
As a design aid, Table 1 shows the value of the θ
JA
of
TO-252 for different heatsink area. The copper patterns that
we used to measure these θ
JA
are shown at the end of the
Application Note Section. reflects the same test results as
what are in the Table 1
shows the maximum allowable power dissipation vs. ambi-
ent temperature for theTO-252 device. shows the maximum
allowable power dissipation vs. copper area (in
2
) for the
TO-252 device. Please see AN1028 for power enhancement
techniques to be used with TO-252 package.
01048423
FIGURE 1. Cross-sectional view of Integrated Circuit
Mounted on a printed circuit board. Note that the case
temperature is measured at the point where the leads
contact with the mounting pad surface
01048424
FIGURE 2. Power Dissipation Diagram
LM341/LM78MXX Series
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Application Information (Continued)
TABLE 1. θ
JA
Different Heatsink Area
Layout Copper Area Thermal Resistance
Top Sice (in
2
)* Bottom Side (in
2
)(θ
JA
, ˚C/W) TO-252
1 0.0123 0 103
2 0.066 0 87
3 0.3 0 60
4 0.53 0 54
5 0.76 0 52
61047
7 0 0.2 84
8 0 0.4 70
9 0 0.6 63
10 0 0.8 57
11 0 1 57
12 0.066 0.066 89
13 0.175 0.175 72
14 0.284 0.284 61
15 0.392 0.392 55
16 0.5 0.5 53
*Tab of device attached to topside copper
LM341/LM78MXX Series
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Application Information (Continued)
Typical Application
01048409
*Required if regulator input is more than 4 inches from input filter capacitor
(or if no input filter capacitor is used).
**Optional for improved transient response.
01048420
FIGURE 3. θ
JA
vs. 2oz Copper Area for TO-252
01048422
FIGURE 4. Maximum Allowable Power Dissipation vs.
Ambient Temperature for TO-252
01048421
FIGURE 5. Maximum Allowable Power Dissipation vs.
2oz. Copper Area for TO-252
LM341/LM78MXX Series
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Physical Dimensions inches (millimeters) unless otherwise noted
TO-39 Metal Can Package (H)
Order Number LM78M05CH, LM78M12CH or LM78M15CH
NS Package Number H03A
TO-220 Power Package (T)
Order Number LM341T-5.0, LM341T-12, LM341T-15, LM78M05CT, LM78M12CT or LM78M15CT
NS Package Number T03B
LM341/LM78MXX Series
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
TO-252
Order Number LM78M05CDT
NS Package Number TD03B
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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LM341/LM78MXX Series 3-Terminal Positive Voltage Regulators
