LM1085.pdf
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744 KB
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Pobierz
June 2005
LM1085
3A Low Dropout Positive Regulators
General Description
The LM1085 is a series of low dropout positive voltage
regulators with a maximum dropout of 1.5V at 3A of load
current. It has the same pin-out as National Semiconductor’s
industry standard LM317.
The LM1085 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 integrate the adjust resistors.
The LM1085 circuit includes a zener trimmed bandgap ref-
erence, current limiting and thermal shutdown.
The LM1085 series is available in TO-220 and TO-263 pack-
ages. Refer to the LM1084 for the 5A 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
3A
n
Line Regulation
0.015% (typical)
n
Load Regulation
0.1% (typical)
Applications
n
High Efficiency Linear Regulators
n
Battery Charger
n
Post Regulation for Switching Supplies
n
Constant Current Regulator
n
Microprocessor Supply
Connection Diagrams
Application Circuit
TO-220
10094702
Top View
TO-263
10094752
1.2V to 15V Adjustable Regulator
10094704
Top View
Basic Functional Diagram,
Adjustable Version
10094765
© 2005 National Semiconductor Corporation
DS100947
www.national.com
Ordering Information
Package
Temperature Range
Part Number
Transport Media
NSC Drawing
3-lead TO-263
−40˚C to +125˚C
LM1085IS-ADJ
Rails
LM1085ISX-ADJ
Tape and Reel
LM1085IS-12
Rails
TS3B
LM1085ISX-12
Tape and Reel
LM1085IS-3.3
Rails
LM1085ISX-3.3
Tape and Reel
LM1085IS-5.0
Rails
LM1085ISX-5.0
Tape and Reel
3-lead TO-220
−40˚C to + 125˚C
LM1085IT-ADJ
Rails
LM1085IT-12
Rails
T03B
LM1085IT-3.3
Rails
LM1085IT-5.0
Rails
Simplified Schematic
10094734
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
LM1085-ADJ
Junction Temperature (T
J
)(Note 3)
150˚C
Storage Temperature Range
-65˚C to 150˚C
Lead Temperature
260˚C, to 10 sec
ESD Tolerance (Note 4)
2000V
29V
Operating Ratings
(Note 1)
Junction Temperature Range (T
J
) (Note 3)
Control Section
LM1085-12
18V
LM1085-3.3
27V
−40˚C to 125˚C
LM1085-5.0
25V
Output Section
−40˚C to 150˚C
Power Dissipation (Note 2)
Internally Limited
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.
Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Symbol
Parameter
Conditions
Units
V
REF
Reference Voltage
LM1085-ADJ
I
OUT
= 10mA, V
IN
−V
OUT
=3V
10mA
1.238
1.225
1.250
1.250
1.262
1.270
V
V
≤
I
OUT
≤
I
FULL LOAD
,1.5V
≤
(V
IN
−V
OUT
)
≤
15V
(Note 7)
V
OUT
Output Voltage
(Note 7)
LM1085-3.3
I
OUT
= 0mA, V
IN
=5V
0
3.270
3.235
3.300
3.300
3.330
3.365
V
V
≤
I
OUT
≤
I
FULL LOAD
, 4.8V
≤
V
IN
≤
15V
LM1085-5.0
I
OUT
= 0mA, V
IN
=8V
0
4.950
4.900
5.000
5.000
5.050
5.100
V
V
I
OUT
≤
I
FULL LOAD
, 6.5V
V
IN
≤
20V
≤
≤
LM1085-12
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)
LM1085-ADJ
I
OUT
=10mA, 1.5V
≤
(V
IN
-V
OUT
)
≤
15V
0.015
0.035
0.2
0.2
%
%
LM1085-3.3
I
OUT
= 0mA, 4.8V
0.5
1.0
6
6
mV
mV
≤
V
IN
≤
15V
LM1085-5.0
I
OUT
= 0mA, 6.5V
0.5
1.0
10
10
mV
mV
≤
V
IN
≤
20V
LM1085-12
I
OUT
=0mA, 13.5V
1.0
2.0
25
25
mV
mV
≤
V
IN
≤
25V
∆
V
OUT
Load Regulation
(Note 8)
LM1085-ADJ
(V
IN
-V
OUT
) = 3V, 10mA
0.1
0.2
0.3
0.4
%
%
≤
I
OUT
≤
I
FULL LOAD
LM1085-3.3
V
IN
= 5V, 0
3
7
15
20
mV
mV
I
OUT
≤
I
FULL LOAD
≤
LM1085-5.0
V
IN
= 8V, 0
≤
I
OUT
≤
I
FULL LOAD
5
10
20
35
mV
mV
LM1085-12
V
IN
= 15V, 0
≤
I
OUT
≤
I
FULL LOAD
12
24
36
72
mV
mV
Dropout Voltage
(Note 9)
LM1085-ADJ, 3.3, 5, 12
∆
V
REF
,
∆
V
OUT
= 1%, I
OUT
=3A
1.3
1.5
V
3
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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.
Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Symbol
Parameter
Conditions
Units
I
LIMIT
Current Limit
LM1085-ADJ
V
IN
−V
OUT
=5V
V
IN
−V
OUT
= 25V
3.2
0.2
5.5
0.5
A
A
LM1085-3.3
V
IN
=8V
3.2
5.5
A
LM1085-5.0
V
IN
= 10V
3.2
5.5
A
LM1085-12
V
IN
= 17V
3.2
5.5
A
Minimum Load
Current (Note 10)
LM1085-ADJ
V
IN
−V
OUT
= 25V
5.0
10.0
mA
Quiescent Current
LM1085-3.3
V
IN
≤
18V
5.0
10.0
mA
LM1085-5.0
V
IN
≤
20V
5.0
10.0
mA
LM1085-12
V
IN
≤
25V
5.0
10.0
mA
Thermal Regulation
T
A
= 25˚C, 30ms Pulse
.004
0.02
%/W
Ripple Rejection
f
RIPPLE
= 120Hz, C
OUT
= 25µF Tantalum, I
OUT
=3A
LM1085-ADJ, C
ADJ
= 25µF, (V
IN
−V
O
)=3V
LM1085-3.3, V
IN
= 6.3V
60
75
dB
60
72
dB
LM1085-5.0, V
IN
=8V
60
68
dB
LM1085-12 V
IN
= 15V
54
60
dB
Adjust Pin Current
LM1085
55
120
µA
Adjust Pin Current
Change
10mA
≤
I
OUT
≤
I
FULL LOAD
, 1.5V
≤
V
IN
−V
OUT
≤
25V
0.2
5
µA
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
0.7/3.0
0.7/3.0
˚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 is
P
D
=(T
J(max)
–T
A
)/
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
FULL LOAD
is defined in the current limit curves. The I
FULL LOAD
Curve defines the current limit as a function of input-to-output voltage. Note that 30W power
dissipation for the LM1085 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.
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4
Typical Performance Characteristics
Dropout Voltage vs. Output Current
Short-Circuit Current vs. Input/Output Difference
10094768
10094763
Percent Change in Output Voltage vs. Temperature
Adjust Pin Current vs. Temperature
10094799
10094798
Maximum Power Dissipation vs. Temperature
Ripple Rejection vs. Frequency (LM1085-Adj.)
10094743
10094770
5
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