1
LT1083/LT1084/LT1085
s
Three-Terminal Adjustable
s
Output Current of 3A, 5A or 7.5A
s
Operates Down to 1V Dropout
s
Guaranteed Dropout Voltage at Multiple Current Levels
s
Line Regulation: 0.015%
s
Load Regulation: 0.1%
s
100% Thermal Limit Functional Test
s
Fixed Versions Available
The LT
1083 series of positive adjustable regulators are
designed to provide 7.5A, 5A and 3A with higher efficiency
than currently available devices. All internal circuitry is
designed to operate down to 1V input-to-output differen-
tial and the dropout voltage is fully specified as a function
of load current. Dropout is guaranteed at a maximum of
1.5V at maximum output current, decreasing at lower load
currents. On-chip trimming adjusts the reference voltage
to 1%. Current limit is also trimmed, minimizing the stress
on both the regulator and power source circuitry under
overload conditions.
The LT1083/LT1084/LT1085 devices are pin compatible
with older three-terminal regulators. A 10
F output ca-
pacitor is required on these new devices. However, this is
included in most regulator designs.
Unlike PNP regulators, where up to 10% of the output
current is wasted as quiescent current, the LT1083 quies-
cent current flows into the load, increasing efficiency.
7.5A, 5A, 3A Low Dropout
Positive Adjustable Regulators
121
1%
IN
OUT
ADJ
365
1%
10
F
5V AT 7.5A
LT1083
V
IN
6.5V
1083/4/5 ADJ TA01
+
10
F*
TANTALUM
+
*REQUIRED FOR STABILITY
5V, 7.5A Regulator
DEVICE
OUTPUT CURRENT*
LT1083
7.5A
LT1084
5.0A
LT1085
3.0A
*For a 1.5A low dropout regulator see the LT1086 data sheet.
s
High Efficiency Linear Regulators
s
Post Regulators for Switching Supplies
s
Constant Current Regulators
s
Battery Chargers
OUTPUT CURRENT
0
INPUT/OUTPUT VOLTAGE DIFFERENTIAL (V)
2
1
0
1083/4/5 ADJ TA02
I
FULL LOAD
Dropout Voltage vs Output Current
APPLICATIO S
U
FEATURES
TYPICAL APPLICATIO
U
DESCRIPTIO
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
2
LT1083/LT1084/LT1085
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reference Voltage
I
OUT
= 10mA, T
J
= 25
C,
(V
IN
V
OUT
) = 3V
1.238
1.250
1.262
V
10mA
I
OUT
I
FULL LOAD
1.5V
(V
IN
V
OUT
)
25V (Notes 4, 6, 7)
q
1.225
1.250
1.270
V
Line Regulation
I
LOAD
= 10mA, 1.5V
(V
IN
V
OUT
)
15V, T
J
= 25
C (Notes 2, 3)
0.015
0.2
%
q
0.035
0.2
%
M Grade: 15V
(V
IN
V
OUT
)
35V (Notes 2, 3)
q
0.05
0.5
%
C, I Grades: 15V
(V
IN
V
OUT
)
30V (Notes 2, 3)
q
0.05
0.5
%
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
ELECTRICAL CHARACTERISTICS
Power Dissipation ............................... Internally Limited
Input-to-Output Voltage Differential
"C" Grades .......................................................... 30V
"I" Grades ............................................................ 30V
"M" Grades .......................................................... 35V
Operating Junction Temperature Range
"C" Grades: Control Section .................. 0
C to 125
C
Power Transistor ............... 0
C to 150
C
"I" Grades: Control Section ............. 40
C to 125
C
Power Transistor .......... 40
C to 150
C
"M" Grades: Control Section ............. 55
C to 150
C
Power Transistor .......... 55
C to 200
C
Storage Temperature Range ................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
100% thermal shutdown functional test.
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
ORDER PART
NUMBER
ORDER PART
NUMBER
LT1083CP
LT1084CP
LT1084CT
LT1084IT
LT1085CT
LT1085IT
T PACKAGE
3-LEAD PLASTIC TO-220
FRONT VIEW
TAB
IS
OUTPUT
3
2
1
V
IN
V
OUT
ADJ
V
IN
V
OUT
ADJ
P PACKAGE
3-LEAD PLASTIC TO-3P
FRONT VIEW
TAB IS
OUTPUT
3
2
1
1
2
V
IN
CASE IS
OUTPUT
BOTTOM VIEW
ADJ
K PACKAGE
2-LEAD TO-3 METAL CAN
JA
= 35
C/W
JA
= 35
C/W
JA
= 50
C/W
V
IN
V
OUT
ADJ
3
2
1
M PACKAGE
3-LEAD PLASTIC DD
FRONT VIEW
TAB
IS
OUTPUT
3
2
1
*WITH PACKAGE SOLDERED TO 0.5IN
2
COPPER AREA
OVER BACKSIDE GROUND PLANE OR INTERNAL POWER
PLANE.
JA
CAN VARY FROM 20
C/W TO > 40
C/W
DEPENDING ON MOUNTING TECHNIQUE.
JA
= 30
C/W*
LT1083CK
LT1083MK
LT1084CK
LT1084MK
LT1085CK
LT1085MK
LT1085CM
PRECO DITIO I G
U
U
U
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C.
(Note 1)
3
LT1083/LT1084/LT1085
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Load Regulation
(V
IN
V
OUT
) = 3V
10mA
I
OUT
I
FULL LOAD
T
J
= 25
C (Notes 2, 3, 4, 6)
0.1
0.3
%
q
0.2
0.4
%
Dropout Voltage
V
REF
= 1%, I
OUT
= I
FULLLOAD
(Notes 5, 6, 8)
q
1.3
1.5
V
Current Limit
LT1083
(V
IN
V
OUT
) = 5V
q
8.0
9.5
A
(V
IN
V
OUT
) = 25V
q
0.4
1.0
A
LT1084
(V
IN
V
OUT
) = 5V
q
5.5
6.5
A
(V
IN
V
OUT
) = 25V
q
0.3
0.6
A
LT1085
(V
IN
V
OUT
) = 5V
q
3.2
4.0
A
(V
IN
V
OUT
) = 25V
q
0.2
0.5
A
Minimum Load Current
(V
IN
V
OUT
) = 25V
q
5
10
mA
Thermal Regulation
T
A
= 25
C, 30ms Pulse
LT1083
0.002
0.010
%/W
LT1084
0.003
0.015
%/W
LT1085
0.004
0.020
%/W
Ripple Rejection
f = 120Hz, C
ADJ
= 25
F, C
OUT
= 25
F Tantalum
I
OUT
= I
FULL LOAD
, (V
IN
V
OUT
) = 3V (Notes 6, 7, 8)
q
60
75
dB
Adjust Pin Current
T
J
= 25
C
55
A
q
120
A
Adjust Pin Current Change
10mA
I
OUT
I
FULL LOAD
1.5V
(V
IN
V
OUT
)
25V (Note 6)
q
0.2
5
A
Temperature Stability
q
0.5
%
Long Term Stability
T
A
= 125
C, 1000 Hrs
0.3
1
%
RMS Output Noise (% of V
OUT
)
T
A
= 25
C
10Hz =
f
10kHz
0.003
%
Thermal Resistance Junction-to-Case
Control Circuitry/Power Transistor
LT1083
K Package
0.6/1.6
C/W
P Package
0.5/1.6
C/W
LT1084
K Package
0.75/2.3
C/W
P Package
0.65/2.3
C/W
T Package
0.65/2.7
C/W
LT1085
K Package
0.9/3.0
C/W
M, T Packages
0.7/3.0
C/W
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: See thermal regulation specifications for changes in output voltage
due to heating effects. Load and line regulation are measured at a constant
junction temperature by low duty cycle pulse testing.
Note 3: Line and load regulation are guaranteed up to the maximum power
dissapation (60W for the LT1083, 45W for the LT1084 (K, P), 30W for the
LT1084 (T) and 30W for the LT1085). 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 voltage
range.
Note 4: I
FULL LOAD
is defined in the current limit curves. The I
FULLLOAD
curve is defined as the minimum value of current limit as a function of
input-to-output voltage. Note that the 60W power dissipation for the
LT1083 (45W for the LT1084 (K, P), 30W for the LT1084 (T), 30W for the
LT1085) is only achievable over a limited range of input-to-output voltage.
Note 5: Dropout voltage is specified over the full output current range of
the device. Test points and limits are shown on the Dropout Voltage
curve.
Note 6: For LT1083 I
FULL LOAD
is 5A for 55
C
T
J
< 40
C and 7.5A for
T
J
40
C.
Note 7: 1.7V
(V
IN
V
OUT
)
25V for LT1084 at 55
C
T
J
40
C.
Note 8: Dropout is 1.7V maximum for LT1084 at 55
C
T
J
40
C.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C.
4
LT1083/LT1084/LT1085
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
OUTPUT CURRENT (A)
0
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
1
2
LT1083/4/5 ADJ G01
0
1
2
3
4
5
6
7
8
9
10
INDICATES GUARANTEED TEST POINT
40C
T
J
150C
0C
T
J
125C
T
J
= 150C
T
J
= 25C
T
J
= 55C
INPUT/OUTPUT DIFFERENTIAL (V)
0
SHORT-CIRCUIT CURRENT (A)
8
10
12
15
25
LT1083/4/5 ADJ G02
6
4
5
10
20
30
35
2
0
25
C
150
C
I
FULL LOAD
GUARANTEED
55
C
TEMPERATURE (C)
50
0.20
OUTPUT VOLTAGE DEVIATION (%) 0.15
0.10
0.05
0
0
50
100
150
LT1083/4/5 ADJ G03
0.05
0.10
25
25
75
125
I = 7.5A
OUTPUT CURRENT (A)
0
0
MINIMUN INPUT/OUTPUT DIFFERENTIAL (V)
1
1
2
3
4
LT1083/4/5 ADJ G04
5
2
6
INDICATES GUARANTEED TEST POINT
55C
T
J
150C
0C
T
J
125C
T
J
= 150C
T
J
= 55C
T
J
= 25C
INPUT/OUTPUT DIFFERENTIAL (V)
0
0
SHORT-CIRCUIT CURRENT (A)
1
3
4
5
10
7
10
20
25
LT1083/4/5 ADJ G05
2
8
9
6
5
15
30
35
25
C
55
C
150
C
GUARANTEED
I
FULL LOAD
TEMPERATURE (C)
50
0.20
0.15
0.10
0.05
0.05
0.10
OUTPUT VOLTAGE DEVIATION (%)
0
0
50
100
150
LT1083/4/5 ADJ G06
25
25
75
125
I = 5A
TEMPERATURE (C)
50
0.20
0.15
0.10
0.05
0.05
0.10
OUTPUT VOLTAGE DEVIATION (%)
0
0
50
100
150
LT1083/4/5 ADJ G09
25
25
75
125
I = 3A
INPUT/OUTPUT DIFFERENTIAL (V)
0
SHORT-CIRCUIT CURRENT (A)
4
5
6
15
25
LT1083/4/5 ADJ G08
3
2
5
10
20
30
35
1
0
25
C
55
C
I
FULL LOAD
GUARANTEED
150
C
OUTPUT CURRENT (A)
0
0
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
1
2
1
2
LT1083/4/5 ADJ G07
3
4
INDICATES GUARANTEED TEST POINT
T
J
= 150C
T
J
= 25C
55C
T
J
150C
T
J
= 55C
0C
T
J
125C
LT1085
LT1085
LT1085
Dropout Voltage
Short-Circut Current
Load Regulation
LT1084
LT1084
LT1084
Dropout Voltage
Short-Circut Current
Load Regulation
LT1083
LT1083
LT1083
Dropout Voltage
Short-Circut Current
Load Regulation
5
LT1083/LT1084/LT1085
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Minimum Operating Current
Temperature Stability
Adjust Pin Current
INPUT/OUTPUT DIFFERENTIAL (V)
0
0
MINIMUM OPERATING CURRENT (mA)
1
3
4
5
10
7
10
20
25
LT1083/4/5 ADJ G10
2
8
9
6
5
15
30
35
T
J
= 55C
T
J
= 150C
T
J
= 25C
TEMPERATURE (C)
50
1.27
1.26
1.25
1.24
1.23
REFERENCE VOLTAGE (V)
0
50
100
150
LT1083/4/5 ADJ G11
25
25
75
125
TEMPERATURE (C)
50
100
90
80
70
60
50
40
30
20
10
0
ADJUST PIN CURRENT (
A)
0
50
100
150
LT1083/4/5 ADJ G12
25
25
75
125
FREQUENCY (Hz)
RIPPLE REJECTION (dB)
100
90
80
70
60
50
40
30
20
10
0
10
1k
10k
100k
1083/4/5 ADJ G13
100
V
RIPPLE
0.5V
P-P
V
RIPPLE
3V
P-P
(V
IN
V
OUT
)
3V
(V
IN
V
OUT
)
V
DROPOUT
C
ADJ
= 200
F AT FREQUENCIES < 60Hz
C
ADJ
= 25
F AT FREQUENCIES > 60Hz
I
OUT
= 7A
OUTPUT CURRENT (A)
0
RIPPLE REJECTION (dB)
100
90
80
70
60
50
40
30
20
10
0
2
4
5
1083/4/5 ADJ G14
1
3
6
7
8
V
OUT
= 5V
C
ADJ
= 25
F
C
OUT
= 25
F
f
R
= 120Hz
V
RIPPLE
3V
P-P
f
R
= 20kHz
V
RIPPLE
0.5V
P-P
CASE TEMPERATURE (C)
50
POWER (W)
100
90
80
70
60
50
40
30
20
10
0
LT1083/4/5 ADJ G15
60 70 80 90 100 110 120 130 140 150
LT1083MK
LT1083CP
LT1083CK
* AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1083
LT1083
LT1083
Ripple Rejection
Ripple Rejection vs Current
Maximum Power Dissipation*
LT1084
LT1084
LT1084
Ripple Rejection
Ripple Rejection vs Current
Maximum Power Dissipation*
FREQUENCY (Hz)
RIPPLE REJECTION (dB)
100
90
80
70
60
50
40
30
20
10
0
10
1k
10k
100k
1083/4/5 ADJ G16
100
V
RIPPLE
0.5V
P-P
V
RIPPLE
3V
P-P
(V
IN
V
OUT
)
3V
(V
IN
V
OUT
)
V
DROPOUT
C
ADJ
= 200
F AT FREQUENCIES < 60Hz
C
ADJ
= 25
F AT FREQUENCIES > 60Hz
I
OUT
= 5A
OUTPUT CURRENT (A)
0
RIPPLE REJECTION (dB)
100
90
80
70
60
50
40
30
20
10
0
2
4
5
1083/4/5 ADJ G17
1
3
V
OUT
= 5V
C
ADJ
= 25
F
C
OUT
= 25
F
f
R
= 120Hz
V
RIPPLE
3V
P-P
f
R
= 20kHz
V
RIPPLE
0.5V
P-P
CASE TEMPERATURE (C)
50
POWER (W)
60
50
40
30
20
10
0
LT1083/4/5 ADJ G18
60 70 80 90 100 110 120 130 140 150
LT1084MK
LT1084CT
LT1084CP
* AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1084CK
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