LM79MXX Series
3-Terminal Negative Regulators
General Description
The LM79MXX series of 3-terminal regulators is available
with fixed output voltages of -5V, -12V, and -15V. These
devices need only one external component -- a compensa-
tion capacitor at the output. The LM79MXX series is pack-
aged in the TO-220 power package, and is capable of sup-
plying 0.5A of output current.
These regulators employ internal current limiting, safe area
protection, and thermal shutdown for protection against vir-
tually all overload conditions.
Low ground pin current of the LM79MXX series allows out-
put voltage to be easily boosted above the preset value with
a resistor divider. The low quiescent current of these devices
with a specified maximum change with line and load ensures
good regulation in the voltage boosted mode.
For output voltage other than -5V, -12V, and -15V the
LM137 series provides an output voltage range from -1.2V
to -57V.
Features
n
Thermal, short circuit and safe area protection
n
High ripple rejection
n
0.5A output current
n
4% tolerance on preset output voltage
Connection Diagram
TO-220 Plastic Package (T)
DS010483-7
Front View
Order Number LM79M05CT, LM79M12CT or LM79M15CT
See NS Package Number T03B
September 2001
LM79MXX
Series
3-T
erminal
Negative
Regulators
2001 National Semiconductor Corporation
DS010483
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.
Input Voltage
V
O
= -5V
-25V
V
O
= -12V, -15V
-35V
Input/Output Differential
V
O
= -5V
V
O
= -12V, -15V
25V
30V
Power Dissipation (Note 2)
Internally Limited
Operating Junction
Temperature Range
0C to +125C
Storage Temperature Range
-65C to +150C
Lead Temperature
(Soldering, 10 sec.)
230C
ESD Susceptibility
TBD
Electrical Characteristics LM79M05C
Conditions unless otherwise noted: I
OUT
= 350mA, C
IN
= 2.2F, C
OUT
= 1F, 0C
T
J
+125C
Part Number
LM79M05C
Output Voltage
-5V
Units
Input Voltage (Unless Otherwise Specified)
-10V
Symbol
Parameter
Conditions
Min
Typ
Max
V
O
Output Voltage
T
J
= 25C
-4.8
-5.0
-5.2
V
5mA
I
OUT
350mA
-4.75
-5.25
V
(-25
V
IN
-7)
V
O
Line Regulation
T
J
= 25C (Note 3)
8
50
mV
(-25
V
IN
-7)
2
30
mV
(-18
V
IN
- 8)
V
O
Load Regulation
T
J
= 25C, (Note 3)
30
100
mV
5mA
I
OUT
0.5A
I
Q
Quiescent Current
T
J
= 25C
1
2
mA
I
Q
Quiescent Current
With Input Voltage
0.4
mA
Change
(-25
V
IN
-8)
With Load,
5mA
I
OUT
350mA
0.4
mA
V
n
Output Noise Voltage
T
A
= 25C,
150
V
10Hz
f
100Hz
Ripple Rejection
f = 120Hz
54
66
dB
(-18
V
IN
-8)
Dropout Voltage
T
J
= 25C, I
OUT
= 0.5A
1.1
V
I
OMAX
Peak Output Current
T
J
= 25C
800
mA
Average Temperature
I
OUT
= 5mA,
Coefficient of
0C
T
J
100C
-0.4
mV/C
Output Voltage
LM79MXX
Series
www.national.com
2
Electrical Characteristics LM79M12C, LM79M15C
Conditions unless otherwise noted: I
OUT
= 350mA, C
IN
= 2.2F, C
OUT
= 1 F, 0C
T
J
+125C
Part Number
LM79M12C
LM79M15C
Output Voltage
-12V
-15V
Units
Input Voltage (Unless Otherwise Specified)
-19V
-23V
Symbol
Parameter
Conditions
Min
Typ
Max
Min
Typ
Max
V
O
Output Voltage
T
J
= 25C
-11.5
-12.0
-12.5
-14.4
-15.0
-15.6
V
5 mA
I
OUT
350mA
-11.4
-12.6
-14.25
-15.75
V
(-27
V
IN
-14.5)
(-30
V
IN
-10.5)
V
O
Line Regulation
T
J
= 25C (Note 3)
5
80
5
80
mV
(-30
V
IN
-14.5)
(-30
V
IN
-17.5)
3
50
3
50
mV
(-25
V
IN
- 15)
(-28
V
IN
-18)
V
O
Load Regulation
T
J
= 25C, (Note 3)
30
240
30
240
mV
5mA
I
OUT
0.5A
I
Q
Quiescent Current
T
J
= 25C
1.5
3
1.5
3
mA
I
Q
Quiescent Current
With Input Voltage
0.4
0.4
mA
Change
(-30
V
IN
-14.5)
(-30
V
IN
-27)
With Load,
5mA
I
OUT
350mA
0.4
0.4
mA
V
n
Output Noise
T
A
= 25C,
400
400
V
Voltage
10Hz
f
100Hz
Ripple Rejection
f = 120Hz
54
70
54
70
dB
(-25
V
IN
-15)
(-30
V
IN
-17.5)
Dropout Voltage
T
J
= 25C, I
OUT
= 0.5A
1.1
1.1
V
I
OMAX
Peak Output
Current
T
J
= 25C
800
800
mA
Average Temperature I
OUT
= 5mA,
Coefficient of
0C
T
J
100C
-0.8
-1.0
mV/C
Output Voltage
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Refer to Typical Performance Characteristics and Design Considerations for details.
Note 3: Regulation is measued at a constant junction temperature by pulse testing with a low duty cycle. Changes in output voltage due to heating effects must be
taken into account.
Typical Performance Characteristics
Output Voltage vs. Temperature
DS010483-11
Ripple Rejection
DS010483-12
LM79MXX
Series
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3
Typical Performance Characteristics
(Continued)
Output Impedance
DS010483-13
Minimum Input-Output
Differential
DS010483-14
Quiescent Current vs. Input Voltage
DS010483-15
Quiescent Current vs. Load Current
DS010483-16
Short-Circuit Current
DS010483-17
Maximum Average Power
Dissipation (TO-220)
DS010483-18
LM79MXX
Series
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4
Schematic Diagrams
-5V
DS010483-8
-12V and -15V
DS010483-9
LM79MXX
Series
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5
Design Considerations
The
LM79MXX
fixed
voltage
regulator
series
have
thermal-overload protection from excessive power, internal
short-circuit protection which limits the circuit's maximum
current, and output transistor safe-area compensation for
reducing the output current as the voltage across the pass
transistor is increased.
Although the internal power dissipation is limited, the junc-
tion temperature must be kept below the maximum specified
temperature in order to meet data sheet specifications. To
calculate the maximum junction temperature or heat sink
required, the following thermal resistance values should be
used:
Package
JC
JA
(C/W)
(C/W)
TO-220
3
40
(1)
CA
=
CS
+
SA
Solving for T
J
:
T
J
= T
A
+ P
D
(
JC
+
CA
) or
= T
A
=+ P
D
JA
(Without a Heat Sink)
Where
T
J
= Junction Temperature
T
A
= Ambient Temperature
P
D
= Power Dissipation
JC
= Junction-to-Case Thermal Resistance
CA
= Case-to-Ambient Thermal Resistance
CS
= Case-to-Heat Sink Thermal Resistance
SA
= Heat Sink-to-Ambient Thermal Resistance
JA
= Junction-to-Ambient Thermal Resistance
Typical Applications
Bypass capacitors are necessary for stable operation of the
LM79MXX series of regulators over the input voltage and
output current ranges. Output bypass capacitors will improve
the transient response of the regulator.
The bypass capacitors (2.2F on the input, 1.0F on the
output), should be ceramic or solid tantalum which have
good high frequency characteristics. If aluminum electrolyt-
ics are used, their values should be 10F or larger. The
bypass capacitors should be mounted with the shortest
leads, and if possible, directly across the regulator terminals.
Fixed Regulator
DS010483-2
*
Required if regulator is separated from filter capacitor by more than 3".
For value given, capacitor must be solid tantalum. 25F aluminum
electrolytic may be substituted.
Required for stability. For value given, capacitor must be solid tantalum.
25F aluminum electrolytic may be substituted. Values given may be
increased without limit.
For output capacitance in excess of 100F, a high current diode from input
to output (1N4001, etc.) will protect the regulator from momentary input
shorts.
Variable Output
DS010483-3
*Improves transient response and ripple rejection.
Do not increase beyond 50F.
Select R2 as follows:
LM79M05C
300
LM79M12C
750
LM79M15C
1k
LM79MXX
Series
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6
Typical Applications
(Continued)
Performance (Typical)
(-15)
(+15)
Load Regulation at 0.5A
40mV
2 mV
Output Ripple, C
IN
= 3000F, I
L
= 0.5A
100 Vrms
100 Vrms
Temperature Stability
50mV
50mV
Output Noise 10Hz
f
10kHz
150 Vrms
150 Vrms
15V, 1 Amp Tracking Regulators
DS010483-1
*
Resistor tolerance of R4 and R5 determine matching of (+) and (-) outputs.
**
Necessary only if raw supply filter capacitors are more than 3" from regulators.
Dual Trimmed Supply
DS010483-4
LM79MXX
Series
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7
Physical Dimensions
inches (millimeters) unless otherwise noted
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whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
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www.national.com
TO-220 Plastic Package (T)
Order Number LM79M05CT, LM79M12CT or LM79M15CT
NS Package Number T03B
LM79MXX
Series
3-T
erminal
Negative
Regulators
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.
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