LM1084.pdf
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August 2002
LM1084
5A Low Dropout Positive Regulators
General Description
The LM1084 is a series of low dropout voltage positive
regulators with a maximum dropout of 1.5V at 5A of load
current. It has the same pin-out as National Semiconductor’s
industry standard LM317.
The LM1084 is available in an adjustable version, which can
set the output voltage with only two external resistors. It is
also available in three fixed voltages: 3.3V, 5.0V and 12.0V.
The fixed versions intergrate the adjust resistors.
The LM1084 circuit includes a zener trimmed bandgap ref-
erence, current limiting and thermal shutdown.
The LM1084 series is available in TO-220 and TO-263 pack-
ages. Refer to the LM1085 for the 3A version, and the
LM1086 for the 1.5A version.
Features
n
Available in 3.3V, 5.0V, 12V and Adjustable Versions
n
Current Limiting and Thermal Protection
n
Output Current
5A
n
Industrial Temperature Range
−40˚C to 125˚C
n
Line Regulation
0.015% (typical)
n
Load Regulation
0.1% (typical)
Applications
n
Post Regulator for Switching DC/DC Conveter
n
High Efficiency Linear Regulators
n
Battery Charger
Connection Diagrams
TO-220
Application Circuit
10094636
Top View
TO-263
10094652
1.2V to 15V Adjustable Regulator
10094635
Top View
Basic Functional Diagram, Adjustable Version
10094665
© 2002 National Semiconductor Corporation
DS100946
www.national.com
Ordering Information
Package
Temperature Range
Part Number
Transport Media
NSC Drawing
3-lead TO-263
−40˚C to +125˚C
LM1084IS-ADJ
Rails
LM1084ISX-ADJ
Tape and Reel
LM1084IS-12
Rails
TS3B
LM1084ISX-12
Tape and Reel
LM1084IS-3.3
Rails
LM1084ISX-3.3
Tape and Reel
LM1084IS-5.0
Rails
LM1084ISX-5.0
Tape and Reel
3-lead TO-220
−40˚C to + 125˚C
LM1084IT-ADJ
Rails
LM1084IT-12
Rails
T03B
LM1084IT-3.3
Rails
LM1084IT-5.0
Rails
Simplified Schematic
10094634
www.national.com
2
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Maximum Input to Output Voltage Differential
LM1084-ADJ
Storage Temperature Range
-65˚C to 150˚C
Lead Temperature
260˚C, to 10 sec
ESD Tolerance
(Note 4)
2000V
Operating Ratings
(Note 1)
29V
Junction Temperature Range (T
J
)
(Note 3)
Control Section
LM1084-12
18V
−40˚C to 125˚C
LM1084-3.3
27V
Output Section
−40˚C to 150˚C
LM1084-5.0
25V
Power Dissipation
(Note 2)
Internally Limited
Junction Temperature (T
J
)
(Note 3)
150˚C
Electrical Characteristics
Typicals and limits appearing in normal type apply for T
J
= 25˚C. Limits appearing in
Boldface
type apply over the entire junc-
tion temperature range for operation.
Symbol
Parameter
Conditions
Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
V
REF
Reference Voltage
LM1084-ADJ
I
OUT
= 10mA, V
IN
−V
OUT
=3V
10mA
≤
I
OUT
≤
I
FULL LOAD
,1.5V
≤
(V
IN
−V
OUT
)
≤
25V
(Note 7)
1.238
1.225
1.250
1.250
1.262
1.270
V
V
V
OUT
Output Voltage
(Note 7)
LM1084-3.3
I
OUT
= 0mA, V
IN
=8V
0
≤
I
OUT
≤
I
FULL LOAD
, 4.8V
≤
V
IN
≤
15V
3.270
3.235
3.300
3.300
3.330
3.365
V
V
LM1084-5.0
I
OUT
= 0mA, V
IN
=8V
0
I
OUT
≤
I
FULL LOAD
, 6.5V
≤
V
IN
≤
20V
4.950
4.900
5.000
5.000
5.050
5.100
V
V
LM1084-12
I
OUT
= 0mA, V
IN
= 15V
0
I
OUT
≤
I
FULL LOAD
, 13.5V
≤
V
IN
≤
25V
11.880
11.760
12.000
12.000
12.120
12.240
V
V
∆
V
OUT
Line Regulation
(Note 8)
LM1084-ADJ
I
OUT
=10mA, 1.5V
0.015
0.035
0.2
0.2
%
%
≤
(V
IN
-V
OUT
)
≤
15V
LM1084-3.3
I
OUT
= 0mA, 4.8V
≤
V
IN
≤
15V
0.5
1.0
6
6
mV
mV
LM1084-5.0
I
OUT
= 0mA, 6.5V
≤
V
IN
≤
20V
0.5
1.0
10
10
mV
mV
LM1084-12
I
OUT
=0mA, 13.5V
≤
V
IN
≤
25V
1.0
2.0
25
25
mV
mV
∆
V
OUT
Load Regulation
(Note 8)
LM1084-ADJ
(V
IN
-V
OUT
) = 3V, 10mA
≤
I
OUT
≤
I
FULL LOAD
0.1
0.2
0.3
0.4
%
%
LM1084-3.3
V
IN
= 5V, 0
≤
I
OUT
≤
I
FULL LOAD
3
7
15
20
mV
mV
LM1084-5.0
V
IN
= 8V, 0
≤
I
OUT
≤
I
FULL LOAD
5
10
20
35
mV
mV
LM1084-12
V
IN
= 15V, 0
≤
I
OUT
≤
I
FULL LOAD
12
24
36
72
mV
mV
Dropout Voltage
(Note 9)
LM1084-3.3/5/12/ADJ
∆
1.3
1.5
V
3
www.national.com
≤
≤
V
REF
= 1%, I
OUT
=5A
Electrical Characteristics
(Continued)
Typicals and limits appearing in normal type apply for T
J
= 25˚C. Limits appearing in
Boldface
type apply over the entire junc-
tion temperature range for operation.
Symbol
Parameter
Conditions
Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
I
LIMIT
Current Limit
LM1084-ADJ
V
IN
−V
OUT
=5V
V
IN
−V
OUT
= 25V
5.5
0.3
8.0
0.6
A
A
LM1084-3.3
V
IN
=8V
5.5
8.0
A
LM1084-5.0
V
IN
= 10V
5.5
8.0
A
LM1084-12
V
IN
= 17V
5.5
8.0
A
Minimum Load
Current
(Note 10)
LM1084-ADJ
V
IN
−V
OUT
= 25V
5
10.0
mA
Quiescent Current
LM1084-3.3
V
IN
= 18V
5.0
10.0
mA
LM1084-5.0
V
IN
20V
5.0
10.0
mA
LM1084-12
V
IN
≤
25V
5.0
10.0
mA
Thermal Regulation T
A
= 25˚C, 30ms Pulse
0.003
0.015
%/W
Ripple Rejection
f
RIPPLE
= 120Hz, = C
OUT
= 25µF Tantalum,
I
OUT
=5A
LM1084-ADJ, C
ADJ
, = 25µF, (V
IN
−V
O
)=3V
LM1084-3.3, V
IN
= 6.3V
60
75
dB
60
72
dB
LM1084-5.0, V
IN
=8V
60
68
dB
LM1084-12 V
IN
= 15V
54
60
dB
Adjust Pin Current
LM1084
55
120
µA
Adjust Pin Current
Change
10mA
≤
I
OUT
≤
I
FULL LOAD
,
0.2
5
µA
1.5V
≤
V
IN
−V
OUT
≤
25V
Temperature
Stability
0.5
%
Long Term Stability T
A
=125˚C, 1000Hrs
0.3
1.0
%
RMS Output Noise
(% of V
OUT
)
10Hz
≤
f
≤
10kHz
0.003
%
Thermal Resistance
Junction-to-Case
3-Lead TO-263: Control Section/Output Section
3-Lead TO-220: Control Section/Output Section
0.65/2.7
0.65/2.7
˚C/W
˚C/W
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 specific performance is not guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics.
Note 2:
Power dissipation is kept in a safe range by current limiting circuitry. Refer to Overload Recovery in Application Notes.
Note 3:
The maximum power dissipation is a function of T
J(max)
,
θ
JA
, and T
A
. The maximum allowable power dissipation at any ambient temperature
θ
JA
. All numbers apply for packages soldered directly into a PC board. Refer to Thermal Considerations in the Application Notes.
Note 4:
For testing purposes, ESD was applied using human body model, 1.5k
Ω
in series with 100pF.
Note 5:
Typical Values represent the most likely parametric norm.
Note 6:
All limits are guaranteed by testing or statistical analysis.
Note 7:
I
FULLLOAD
is defined in the current limit curves. The I
FULLLOAD
Curve defines the current limit as a function of input-to-output voltage. Note that 30W power
dissipation for the LM1084 is only achievable over a limited range of input-to-output voltage.
Note 8:
Load and line regulation are measured at constant junction temperature, and are guaranteed up to the maximum power dissipation of 30W. Power
dissipation is determined by the input/output differential and the output current. Guaranteed maximum power dissipation will not be available over the full input/output
range.
Note 9:
Dropout voltage is specified over the full output current range of the device.
Note 10:
The minimum output current required to maintain regulation.
www.national.com
4
≤
is P
D
=(T
J(max)
–T
A
)/
Typical Performance Characteristics
Dropout Voltage (V
IN
−V
OUT
)
Short-Circuit Current
10094663
10094671
Load Regulation
LM1084-ADJ Ripple Rejection
10094638
10094643
LM1084-ADJ Ripple Rejection vs Current
Temperature Stability
10094690
10094625
5
www.national.com
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