LINER LT1085CT 3a, 5a, 7.5a low dropout positive fixed regulator Datasheet

LT1083/84/85 Fixed
3A, 5A, 7.5A Low Dropout
Positive Fixed Regulators
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DESCRIPTION
FEATURES
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Three-Terminal 3.3V, 3.6V, 5V and 12V
Output Current of 3A, 5A or 7.5A
Operates Down to 1V Dropout
Guaranteed Dropout Voltage at Multiple Current Levels
Line Regulation: 0.015%
Load Regulation: 0.1%
100% Thermal Limit Functional Test
Adjustable Versions Available
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APPLICATIONS
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High Efficiency Linear Regulators
Post Regulators for Switching Supplies
Constant Current Regulators
Battery Chargers
The LT1083 series of positive adjustable regulators are
designed to provide 3A, 5A and 7.5A with higher efficiency
than currently available devices. All internal circuitry is
designed to operate down to 1V input to output differential
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 output voltage to
1%. Current limit is also trimmed, minimizing the stress
on both the regulator and power source circuitry under
overload conditions.
The 1083 series devices are pin compatible with older
three-terminal regulators. A 10µF output capacitor is
required on these new devices; however, this is usually
included in most regulator designs.
DEVICE
OUTPUT CURRENT*
LT1083
LT1084
LT1085
7.5 Amps
5.0 Amps
3.0 Amps
Unlike PNP regulators, where up to 10% of the output
current is wasted as quiescent current, the LT1083 quiescent current flows into the load, increasing efficiency.
*For a 1.5A low dropout regulator see the LT1086 data sheet.
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TYPICAL APPLICATION
5V, 7.5A Regulator
5V AT 7.5A
LT1083-5
+
+
10µF
*REQUIRED FOR STABILITY
22µF*
TANTALUM
LT1083/4/5 TA01
INPUT/OUTPUT VOLTAGE DIFFERENTIAL (V)
VIN ≥ 6.5V
Dropout Voltage vs Output Current
2
1
0
0
IFULL LOAD/2
OUTPUT CURRENT (A)
IFULL LOAD
1083/4/5 TA02
1
LT1083/84/85 Fixed
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ABSOLUTE MAXIMUM RATINGS
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
Note 1: Although the devices maximum operating voltage is limited, (20V
for a 3V, 5V device, and 25V for a 12V device) the devices are guaranteed
to withstand transient input voltages up to 30V. For input voltages greater
than the maximum operating input voltage some degradation of
specifications will occur. For input/output voltage differentials greater than
15V, a minimum external load of 5mA is required to maintain regulation.
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Power Dissipation............................... Internally Limited
Input Voltage (Note 1) ............................................. 30V
Operating Input Voltage
3.3V, 3.6V Devices ............................................ 20V
5V Devices ........................................................ 20V
12V Devices ...................................................... 25V
Operating Junction Temperature Range
“C” Grades
Control Section ............................... 0°C to 125°C
Power Transistor ............................. 0°C to 150°C
“M” Grades
Control Section ........................... –55°C to 150°C
Power Transistor ......................... –55°C to 200°C
PRECONDITIONING
100% Thermal Limit Functional Test.
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PACKAGE/ORDER INFORMATION
CASE IS
OUTPUT
VIN
ORDER PART NUMBER
LT1083CK-5
LT1083CK-12
LT1083MK-5
LT1083MK-12
LT1084CK-5
LT1084CK-12
2
1
GND
K PACKAGE
2-LEAD TO-3 METAL CAN
LT1084MK-5
LT1084MK-12
LT1085CK-5
LT1085CK-12
LT1085MK-5
LT1085MK-12
TAB IS
OUTPUT
3
VIN
2
VOUT
1
GND
LT1083CP-5
LT1083CP-12
LT1084CP-5
LT1084CP-12
P PACKAGE
3-LEAD TO-3P PLASTIC
θJA = 45°C/W
θJA = 35°C/W
FRONT VIEW
TAB IS
OUTPUT
ORDER PART NUMBER
FRONT VIEW
3
VIN
2
VOUT
1
GND
T PACKAGE
3-LEAD PLASTIC TO-220
θJA = 50°C/W
LT1084CT-3.3
LT1084CT-5
LT1084CT-12
LT1085CT-3.3
LT1085CT-3.6
LT1085CT-5
LT1085CT-12
FRONT VIEW
TAB IS
OUTPUT
3
VIN
2
VOUT
1
GND
LT1085CM-3.3
LT1085CM-3.6
M PACKAGE
3-LEAD PLASTIC DD
θJA = 30°C/W*
* WITH PACKAGE SOLDERED TO 0.52IN2
COPPER AREA OVER BACKSIDE GROUND
PLANE OR INTERNAL POWER PLANE. θJA CAN
VARY FROM 20°C/W TO > 40°C/W DEPENDING
ON MOUNTING TECHNIQUE.
Consult factory for Industrial grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER
Output Voltage
CONDITIONS
LT1084-3.3
LT1085-3.3
LT1085-3.6
2
IOUT = 0mA, TJ = 25°C, VIN = 8V (K Package Only)
0 ≤ IOUT ≤ 5A, 4.8V ≤ VIN ≤ 15V (Note 8)
VIN = 5V, IOUT = 0mA, TJ = 25°C (K Package Only)
4.8V ≤ VIN ≤ 15V, 0 ≤ IOUT ≤ 3A (Note 8)
VIN = 5V, IOUT = 0mA, TJ = 25°C (K Package Only)
5V ≤ VIN ≤ 15V, 0 ≤ IOUT ≤ 3A (Note 8)
5V ≤ VIN ≤ 15V, 0 ≤ IOUT ≤ 3A, TJ ≥ 0°C (Note 8)
●
●
●
MIN
3.270
3.235
3.270
3.235
3.564
3.500
3.528
TYP
3.300
3.300
3.300
3.300
3.600
MAX
3.330
3.365
3.330
3.365
3.636
3.672
3.672
UNITS
V
V
V
V
V
V
V
LT1083/84/85 Fixed
ELECTRICAL CHARACTERISTICS
PARAMETER
Output Voltage
CONDITIONS
LT1085-3.6
LT1083/4/5-5
LT1083/4/5-12
Line Regulation
LT1084-3.3
5V ≤ VIN ≤ 15V, 0 ≤ IOUT ≤ 2.5A (Note 8)
VIN = 4.75V, IOUT = 3A, TJ ≥ 0°C
VIN = 4.75V, IOUT = 2.5A, TJ ≥ 0°C
VIN = 4.75V, IOUT = 1.5A, TJ > 0°C
IOUT = 0mA, TJ = 25°C, VIN = 8V (K Package Only)
0 ≤ IOUT ≤ IFULLOAD, 6.5V ≤ VIN ≤ 20V (Notes 3, 5, 6, 8)
IOUT = 0mA, TJ = 25°C, VIN = 15V (K Package Only)
0 ≤ IOUT ≤ IFULLOAD, 13.5V ≤ VIN ≤ 25V (Notes 3, 5, 6, 8)
IOUT = 0mA, TJ = 25°C, 4.8V ≤ VIN ≤ 15V
●
MIN
3.528
3.350
3.450
3.528
4.950
4.900
11.880
11.760
●
LT1085-3.3
4.8V ≤ VIN ≤ 15V, IOUT = 0mA, TJ= 25°C
●
LT1085-3.6
4.8V ≤ VIN ≤ 15V, IOUT = 0mA, TJ= 25°C
●
LT1083/4/5-5
IOUT = 0mA, TJ = 25°C, 6.5V ≤ VIN ≤ 20V (Notes 1, 2)
●
LT1083/4/5-12
IOUT = 0mA, TJ = 25°C, 13.5V ≤ VIN ≤ 25V (Notes 1, 2)
●
Load Regulation
LT1084-3.3
VIN = 5V, 0 ≤ IOUT ≤ 5A, TJ = 25°C
●
LT1085-3.3
VIN = 5V, 0 ≤ IOUT ≤ 3A, TJ = 25°C
●
LT1085-3.6
VIN = 5.25V, 0 ≤ IOUT ≤ 3A, TJ = 25°C
●
LT1083/4/5-5
VIN = 8V, 0 ≤ IOUT ≤ IFULLLOAD, TJ = 25°C (Notes 1, 2, 3, 5)
●
LT1083/4/5-12
Dropout Voltage
Current Limit
Quiescient Current
Thermal Regulation
Ripple Rejection
VIN = 15V, 0 ≤ IOUT ≤ IFULLLOAD, TJ = 25°C (Notes 1, 2, 3, 5)
LT1084/5-3.3
∆VOUT = 33mV, IOUT = IFULL LOAD (Notes 4, 5)
LT1085-3.6
∆VOUT = 36mV, IOUT = IFULL LOAD (Notes 4, 5)
LT1083/4/5-5
∆VOUT = 50mV, IOUT = IFULL LOAD (Notes 4, 5)
LT1083/4/5-12
∆VOUT = 120mV, IOUT = IFULL LOAD (Notes 4, 5)
LT1083-5
VIN = 10V
LT1083-12
VIN = 17V
LT1084-3.3
VIN = 8V
LT1084-5
VIN = 10V
LT1084-12
VIN = 17V
LT1085-3.3/3.6 VIN = 8V
LT1085-5
VIN = 10V
LT1085-12
VIN = 17V
LT1084-3.3
VIN = 18V
LT1085-3.3
VIN = 18V
LT1085-3.6
VIN = 18V
LT1083/4/5-5
VIN ≤ 20V
LT1083/4/5-12
VIN ≤ 25V
LT1083-5/12
TA = 25°C, 30ms pulse
LT1084-3.3/5/12
LT1085-3.3/3.6/5/12
f = 120Hz, COUT = 25µF Tantalum, IOUT = IFULLLOAD
LT1084-3.3
f = 120Hz, COUT = 25µF Tantalum, IOUT = 5A, VIN = 6.3V
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
8.0
8.0
5.5
5.5
5.5
3.2
3.2
3.2
●
60
TYP
MAX
3.672
3.672
3.672
3.672
5.050
5.100
12.120
12.240
6
6
6
6
6
6
10
10
25
25
15
20
15
20
15
20
20
35
36
72
1.5
1.5
1.5
1.5
5.000
5.000
12.000
12.000
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
1.0
2.0
3
7
3
7
3
7
5
10
12
24
1.3
1.3
1.3
1.3
9.5
9.5
6.5
6.5
6.5
4.0
4.0
4.0
5.0
10.0
5.0
10.0
5.0
10.0
5.0
10.0
5.0
10.0
0.002 0.010
0.003 0.015
0.004 0.020
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UNITS
V
V
V
V
V
V
V
V
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
mV
V
V
V
V
A
A
A
A
A
A
A
A
mA
mA
mA
mA
mA
%/W
%/W
%/W
dB
3
LT1083/84/85 Fixed
ELECTRICAL CHARACTERISTICS
PARAMETER
Ripple Rejection
CONDITIONS
LT1085-3.3
LT1085-3.6
LT1083/4/5-5
LT1083/4/5-12
Temperature Stability
Long Term Stability
RMS Output Noise
(% of VOUT)
Thermal Resistance
Junctrion-to-Case
●
●
●
●
●
f = 120Hz, COUT = 25µF Tantalum, VIN = 6.3V, IOUT = 3A
f = 120Hz, COUT = 25µF Tantalum, VIN = 6.6V, IOUT = 3A
VIN = 8V (Note 5)
VIN = 15V (Note 5)
MIN
60
60
60
54
TA = 125°C, 1000 Hrs.
TA = 25°C,
10Hz = ≤ f ≤ 10kHz
Control Circuitry/Power Transistor (See Applications Information)
LT1083
K Package
P Package
LT1084
K Package
P Package
T Package
LT1085
K Package
T Package
DD Package
The ● denotes the specifications which apply over the full operating
temperature range.
Note 1: 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 2: Line and load regulation are guaranteed up to the maximum power
dissipation (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 range.
Note 3: IFULL LOAD is defined in the current limit curves. The IFULLLOAD
curve is defined as the minimum value of current limit as a function of
TYP
72
72
68
60
0.5
0.03
MAX
UNITS
dB
dB
dB
dB
%
%
1.0
0.003
%
0.6/1.6
0.5/1.6
0.75/2.3
0.65/2.3
0.65/2.7
0.9/3.0
0.7/3.0
0.7/3.0
°C/W
°C/W
°C/W
°C/W
°C/W
°C/W
°C/W
°C/W
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 4: 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 5: For LT1083 IFULL LOAD is 5A for – 55°C ≤ TJ ≤ – 40°C and 7.5A for
TJ ≥ – 40°C.
Note 6: 1.7V ≤ (VIN – VOUT) ≤ 25V for LT1084 at – 55°C ≤ TJ ≤ – 40°C.
Note 7: Dropout voltage 1.7V maximum for LT1084 at – 55 ≤ TJ ≤ – 40°C.
Note 8: Full load current is not available at all input-output voltages.
See Notes 2,3,5.
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1083 Short-Circuit Current
INDICATES GUARANTEED TEST POINT
TJ = 150°C
TJ = 25°C
TJ = –55°C
0
1
2
3 4 5 6 7 8
OUTPUT CURRENT (A)
9
10
LT1083/4/5 FIXED G01
4
OUTPUT VOLTAGE DEVIATION (%)
0°C ≤ TJ ≤ 125°C
0
0.10
∆I = 7.5A
–40°C ≤ TJ ≤ 150°C
1
LT1083 Load Regulation
12
SHORT-CIRCUIT CURRENT (A)
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
LT1083 Dropout Voltage
2
25°C
10
150°C
8
6
–55°C
4
IFULL LOAD
GUARANTEED
2
0
0
20
30
15
25
5
10
INPUT/OUTPUT DIFFERENTIAL (V)
35
LT1083/4/5 FIXED G02
0.05
0
–0.05
–0.10
–0.15
–0.20
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1083/4/5 FIXED G03
LT1083/84/85 Fixed
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1084 Short Circuit Current
2
INDICATES GUARANTEED TEST POINT
∆I = 5A
1
TJ = –55°C
TJ = 25°C
8
7
150°C
25°C
6
5
4
–55°C
3
2
IFULL LOAD
GUARANTEED
1
1
3
4
2
OUTPUT CURRENT (A)
0
6
5
20
15
10
25
30
5
INPUT/OUTPUT DIFFERENTIAL (V)
0.05
0
–0.05
–0.10
–0.15
–0.20
–50 –25
0
0
35
LT1085 Dropout Voltage
LT1085 Load Regulation
6
0.10
INDICATES GUARANTEED TEST POINT
–55°C ≤ TJ ≤ 150°C
TJ = –55°C
TJ = 25°C
TJ = 150°C
5
25°C
4
150°C
3
–55°C
2
IFULL LOAD
GUARANTEED
1
0
0
0
4
20
30
15
25
5
10
INPUT/OUTPUT DIFFERENTIAL (V)
VRIPPLE
≤ 0.5VP-P
60
(VIN – VOUT) ≥ 3V
–0.10
–0.15
–0.20
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1083/4/5 FIXED G09
Temperature Stability
2.0
100
90
80
(VIN – VOUT) ≥ VDROPOUT
40
30
20
IOUT = IFULL LOAD
fR = 120Hz
VRIPPLE ≤ 3VP-P
70
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
60
50
40
30
20
10
0
10
–0.05
LT1083/4/5-5 Ripple Rejection
vs Current
RIPPLE REJECTION (dB)
VRIPPLE ≤ 3VP-P
70
0
LT1083/4/5 FIXED G08
LT1083/4/5-5 Ripple Rejection
80
35
0.05
OUTPUT VOLTAGE CHANGE (%)
2
3
1
OUTPUT CURRENT (A)
LT1083/4/5 FIXED G07
50
OUTPUT VOLTAGE DEVIATION (%)
SHORT-CIRCUIT CURRENT (A)
∆I = 3A
0°C ≤ TJ ≤ 125°C
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1083/4/5 FIXED G06
LT1085 Short-Circuit Current
2
1
0
LT1083/4/5 FIXED G05
LT1083/4/5 FIXEDG04
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
OUTPUT VOLTAGE DEVIATION (%)
0°C ≤ TJ ≤ 125°C
TJ = 150°C
0.10
9
–55°C ≤ TJ ≤ 150°C
0
RIPPLE REJECTION (dB)
LT1084 Load Regulation
10
SHORT-CIRCUIT CURRENT (A)
MINIMUN INPUT/OUTPUT DIFFERENTIAL (V)
LT1084 Dropout Voltage
1.0
0
–1.0
10
100
1k
10k
FREQUENCY (Hz)
100k
1083/4/5 FIXED G10
0
0
0.8
0.2
0.6
0.4
OUTPUT CURRENT (0 TO IFULL LOAD)
1.0
1083/4/5 FIXED G11
–2.0
–50 –25
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1183/4/5 FIXED G12
5
LT1083/84/85 Fixed
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1083/4/5-12 Ripple Rejection
vs Current
LT1083/4/5-12 Ripple Rejection
80
VRIPPLE ≤ 3VP-P
VRIPPLE
≤ 0.5VP-P
70
LT1083 Maximum Power
Dissipation*
100
100
90
90
80
(VIN – VOUT) ≥ 3V
50
40
30
(VIN – VOUT) ≥ VDROPOUT
20
IOUT = IFULL LOAD
10
0
10
100
1k
10k
FREQUENCY (Hz)
100k
fR = 120Hz
VRIPPLE ≤ 3VP-P
70
70
POWER (W)
60
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
80
60
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
50
40
50
40
30
30
20
20
10
10
0
0
0
0.8
0.2
0.6
0.4
OUTPUT CURRENT (0 TO IFULL LOAD)
1083/4/5 FIXED G13
1.0
1083/4/5 FIXED G14
LT1083MK
60
LT1083CP
LT1083CK
50 60 70 80 90 100 110 120 130 140 150
CASE TEMPERATURE (°C)
* AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1083/4/5 FIXED G15
LT1085 Maximum Power
Dissipation*
LT1084 Maximum Power
Dissipation*
60
50
50
40
LT1084MK
30
LT1084CT
LT1084CP
20
10
POWER (W)
POWER (W)
40
30
LT1085MK
20
LT1085CT
10
LT1084CK
LT1085CK
0
0
6
50 60 70 80 90 100 110 120 130 140 150
CASE TEMPERATURE (°C)
* AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
50 60 70 80 90 100 110 120 130 140 150
CASE TEMPERATURE (°C)
* AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1083/4/5 FIXED G16
LT1083/4/5 FIXED G17
LT1083/84/85 Fixed
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BLOCK DIAGRAM
VIN
+
–
THERMAL
LIMIT
GND
LT1083/4/5 BD
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APPLICATIONS INFORMATION
The LT1083 family of three-terminal regulators are easy to
use and have all the protection features that are expected
in high performance voltage regulators. They are short
circuit protected, have safe area protection as well as
thermal shutdown to turn off the regulator should the
temperature exceed about 165°C.
These regulators offer lower dropout voltage and more
precise reference tolerance. Further, the reference stability with temperature is improved over older types of
regulators. The only circuit difference between using the
LT1083 family and older regulators is that they require an
output capacitor for stability.
Stability
The circuit design used in the LT1083 family requires the
use of an output capacitor as part of the device frequency
compensation. For all operating conditions, the addition of
150µF aluminum electrolytic or a 22µF solid tantalum on
the output will ensure stability. Normally capacitors much
smaller than this can be used with the LT1083. Many
different types of capacitors with widely varying charac-
teristics are available. These capacitors differ in capacitor
tolerance (sometimes ranging up to ±100%), equivalent
series resistance, and capacitance temperature coefficient. The 150µF or 22µF values given will ensure stability.
Normally, capacitor values on the order of 100µF are used
in the output of many regulators to ensure good transient
response with heavy load current changes. Output capacitance can be increased without limit and larger values of
output capacitance further improve stability and transient
response of the LT1083 regulators.
Another possible stability problem that can occur in monolithic IC regulators is current limit oscillations. These can
occur because in current limit the safe area protection
exhibits a negative impedance. The safe area protection
decreases the current limit as the input-to-output voltage
increases.That is the equivalent of having a negitive resistance since increasing voltage causes current to decrease.
Negitive resistance during current limit is not unique to the
LT1083 series and has been present on all power IC
regulators. The value of negative resistance is a function
of how fast the current limit is folded back as input-to-
7
LT1083/84/85 Fixed
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APPLICATIONS INFORMATION
output voltage increases. This negative resistance can
react with capacitors or inductors on the input to cause
oscillations during current limiting. Depending on the
value of series resistance, the overall circuitry may end up
unstable. Since this is a system problem, it is not necessarily easy to solve; however it does not cause any problems with the IC regulator and can usually be ignored.
voltage is rising, the input-to-output voltage differential
remains small allowing the regulator to supply large
output currents. With high input voltage a problem can
occur wherein removal of an output short will not allow the
output voltage to recover. Older regulators such as the
7800 series, also exhibited this phenomenon so it is not
unique to the LT1083.
Protection Diodes
The problem occurs with a heavy output load when the
input voltage is high and the output voltage is low, such as
immediately after a removal of a short. The load line for
such a load may intersect the output current curve at two
points. If this happens there are two stable output operating points for the regulator. With this double intersection
the power supply may need to be cycled down to zero and
brought up again to make the output recover.
In normal operation the LT1083 family does not need any
protection diodes, The internal diode between the input
and the output pins of the LT1083 family can handle
microsecond surge currents of 50A to 100A. Even with
large output capacitances it is very difficult to get those
values of surge current in normal operation. Only with high
value output capacitors, such as 1000µF to 5000µF and
with the input pin instantaneously shorted to ground, can
damage occur. A crowbar circuit at the input of the LT1083
can generate those kinds of currents and a diode from
output-to-input is then recommended. Normal power supply cycling or even plugging and unplugging in the system
will not generate currents large enough to do any damage.
D1
1N4002
(OPTIONAL)
Ripple Rejection
In applications that require improved ripple rejection the
LT1083 series adjustable regulators should be used. With
LT1083 series adjustable regulators the addition of a
bypass capacitor from the adjust pin to ground will reduce
output ripple by the ratio of VOUT/1.25V. See LT1083
series adjustable regulator data sheet.
Load Regulation
VIN
IN
LT1083
ADJ
VOUT
OUT
+
COUT
150µF
LT1083/4/5 AI01
Overload Recovery
Like any of the IC power regulators, the LT1083 has safe
area protection. The safe area protection decreases the
current limit as input-to-output voltage increases and
keeps the power transistor inside a safe operating region
for all values of input-to-output voltage. The LT1083
protection is designed to provide some output current at
all values of input-to-output voltage up to the device
breakdown.
When power is first turned on, as the input voltage rises,
the output follows the input, allowing the regulator to start
up into very heavy loads. During the start-up, as the input
8
Because the LT1083 is a three-terminal device, it is not
possible to provide true remote load sensing. Load regulation will not be limited by the resistance of the wire
connecting the regulator to the load. The data sheet
specification for the load regulation is measured at the
bottom of the package. Negative side sensing is a true
Kelvin connection, with the ground pin of the device
returned to the negative side of the load.
Thermal Considerations
The LT1083 series of regulators have internal power and
thermal limiting circuitry designed to protect the device
under overload conditions. For continuous normal load
conditions however, maximum junction temperature ratings must not be exceeded. It is important to give careful
consideration to all sources of thermal resistance from
junction to ambient. This includes junction-to-case, caseto-heat sink interface, and heat sink resistance itself. New
LT1083/84/85 Fixed
U
U
W
U
APPLICATIONS INFORMATION
thermal resistance specifications have been developed to
more accurately reflect device temperature and ensure
safe operating temperatures. The data section for these
new regulators provides a separate thermal resistance and
maximum junction temperature for both the Control Section and the Power Section. Previous regulators, with a
single junction-to-case thermal resistance specification,
used an average of the two values provided here and
therefore could allow excessive junction temperatures
under certain conditions of ambient temperature and heat
sink resistance. To avoid this possibility, calculations
should be made for both sections to ensure that both
thermal limits are met.
For example, using a LT1083-5CK (TO-3, Commercial)
and assuming:
VIN(max continuous) = 9V, VOUT = 5V, IOUT = 6A,
TA = 75°C θHEAT SINK = 1°C/W,
θCASE-TO-HEAT SINK = 0.2°C/W for K package with
thermal compound.
Power dissipation under these conditions is equal to:
PD = (VIN – VOUT) (IOUT) = 24W
Junction temperature will be equal to:
TJ = TA + PD (θHEAT SINK + θCASE-TO-HEAT SINK + θJC)
For the Control Section:
TJ = 75°C + 24W (1°C/W + 0.2°C/W + 0.6°C/W) =
118°C
118°C < 125°C = TJMAX (Control Section Commercial Range)
For the Power Transistor:
TJ = 75°C + 24W (1°C/W + 0.2°C/W + 1.6°C/W) =
142°C
142°C < 150°C = TJMAX (Power Transistor Commercial Range)
In both cases the junction temperature is below the
maximum rating for the respective sections, ensuring
reliable operation.
Junction-to-case thermal resistance is specified from the
IC junction to the bottom of the case directly below the die.
This is the lowest resistance path for heat flow. Proper
mounting is required to ensure the best possible thermal
flow from this area of the package to the heat sink. Thermal
compound at the case-to-heat sink interface is strongly
recommended. If the case of the device must be electronically isolated, a thermally conductive spacer can be used
as long as its added contribution to thermal resistance is
considered. Note that the case of all devices in this series
is electronically connected to the ouput.
U
TYPICAL APPLICATIONS
High Efficiency Regulator
1mH
28V
INPUT
IN
+
470Ω
MR1122
1N914
28V
1k
OUTPUT
GND
10,000µF
10k
LT1083-5 OUT
1M
4N28
10k
+
LT1011
10k
–
28V
1N914
LT1083/4/5 TA03
9
LT1083/84/85 Fixed
U
TYPICAL APPLICATIONS
Paralleling Regulators
VIN
IN
2 FEET #18 WIRE*
LT1083-5 OUT
GND
VOUT = 5V
IOUT = 0A TO 15A
0.015Ω
IN
LT1083-5 OUT
*THE #18 WIRE ACTS
AS BALLAST RESISTANCE
INSURING CURRENT SHARING
BETWEEN BOTH DEVICES
GND
LT1083/4/5 TA04
7.5A Regulator
T1
TRIAD
F-269U
L
1MH
C30B
IN
20Ω
3
110VAC
20Ω
T2
1
4
+ C1
1N4003
12V
0A TO 7.5A
LT1083-12 OUT
+
GND
100µF
50,000µF
LT1004-1.2
2
C30B
1N914
1N4003
1N4003
1µF
16k*
560Ω
16k*
15V
82k
15k
8
2
–15V
+
7
LT1011
10k
1N4148
3
11k*
200k
4
–
0.1µF
1
NC
100pF
15V
8
–15V
4
7
* 1% FILM RESISTOR
L-DALE TO-5 TYPE
T2-STANCOR 11Z-2003
2N3904
–
3
+
2
1
8
LT1011
10k
6
REGULATOR WITH SCR PREREGULATOR TO
LOWER POWER DISSIPATION. ABOUT 1.7V
DIFFERENTIAL IS MAINTAINED ACROSS THE
LT1083 INDEPENDENT OF LOAD CURRENT.
3
LM301A
1
15k
+
7
–
2
4
–15V
15V
11k*
15V
1µF
LT1083/4/5 TA05
10
LT1083/84/85 Fixed
U
TYPICAL APPLICATIONS
Adjusting Output Voltage
VIN > 12V
Regulator with Reference
LT1085-5
VIN > 11.5V
5V to 10V
+
+
100µF
10µF
10V
LT1085-5
+
+
100µF
10µF
5VOUT
+
10µF*
LT1029
1k
LT1083/4/5 TA06
LT1083/4/5 TA07
*OPTIONAL IMPROVES RIPPLE REJECTION
Low Dropout Negative Supply
IN
VIN
LT1084-12 OUT
GND
+
+
100µF
10,000µF
VOUT = –12V
FLOATING INPUT
LT1083/4/5 TA08
Battery Backed Up Regulated Supply
VIN
5.2V LINE
5.0V BATTERY
LT1084-5
+
10µF
50Ω
SELECT
FOR
CHARGE
RATE
LT1084-5
6.5V
+
10µF
+
100µF
LT1083/4/5 TA09
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
11
LT1083/84/85 Fixed
U
PACKAGE DESCRIPTION
Dimension in inches (millimeters) unless otherwise noted.
M Package
3-Lead Plastic DD
0.401 ± 0.015
(10.185 ± 0.381)
0.060
(1.524)
T Package
3-Lead Plastic TO-220
0.079 – 0.135
(2.007 – 3.429)
0.175 ± 0.008
(4.445 ± 0.203)
(
+0.305
8.407 –0.508
+0.008
0.004 –0.004
+0.203
0.102 –0.102
0.059
(1.499)
TYP
)
(
(
+0.305
3.632 –0.508
0.100 ± 0.010
(2.5402 ± 0.254)
0.050 ± 0.008
(1.270 ± 0.203)
)
0.022 ± 0.005
(0.559 ± 0.127)
0.169 – 0.185
(4.293 – 4.699)
0.035 – 0.055
(0.889 – 1.397)
0.235 – 0.270
(5.969 – 6.858)
)
0.105 ± 0.008
(2.667 ± 0.203)
+0.012
0.143 –0.020
0.139 – 0.153
(3.531 – 3.886)
DIA
0.050 ± 0.008
(1.270 ± 0.203)
15° TYP
+0.012
0.331 –0.020
0.380 – 0.420
(9.652 – 10.668)
0.560 – 0.650
(14.224 – 16.510)
1.005 – 1.080
(25.527 – 27.432)
0.050 ± 0.012
(1.270 ± 0.305)
0.150
3.810
MIN
DD3 0693
0.015 – 0.025
(0.381 – 0.635)
0.027 – 0.037
(0.686 – 0.940)
0.050
(1.270)
TYP
0.090 – 0.110
(2.286 – 2.794)
0.079 – 0.115
(2.007 – 2.921)
T3 0693
K Package
2-Lead TO-3 Metal Can
P Package
3-Lead TO-3P Plastic
0.187 – 0.207
(4.75 – 5.26)
0.620 – 0.64O
(15.75 – 16.26)
0.760 – 0.775
(19.30 – 19.69)
0.320 – 0.350
(8.13 – 8.89)
MOUNTING HOLE
18° – 22°
0.115 – 0.145
(2.92 – 3.68)
DIA
0.060 – 0.135
(1.524 – 3.429)
0.170 – 0.2OO
(4.32 – 5.08)
0.830 – 0.870
(21.08 – 22.10)
0.420 – 0.480
(10.67 – 12.19)
EJECTOR PIN MARKS
0.105 – 0.125
(2.67 – 3.18)
DIA
0.580 – 0.6OO
(14.73 – 15.24)
0.038 – 0.043
(0.965 – 1.09)
1.177 – 1.197
(29.90 – 30.40)
3° – 7°
0.067 – 0.077
(1.70 – 1.96)
0.210 – 0.220
(5.33 – 5.59)
0.780 – 0.800 0.170
(19.81 – 20.32) (4.32)
MAX
0.152 – 0.161
(3.86 – 4.09)
DIA
0.167 – 0.177
(4.24 – 4.49)
R TYP
0.425 – 0.435
(10.80 – 11.05)
0.655 – 0.675
(16.64 – 17.15)
0.042 – 0.052
(1.07 – 1.32)
0.495 – 0.525
(12.57 – 13.34)
0.215
(5.46)
BSC
Linear Technology Corporation
0.087 – 0.102
(2.21 – 2.59)
0.020 – 0.040
(0.51 – 1.02)
K2 0592
0.074 – 0.084
(1.88 – 2.13)
12
0.060 – 0.080
(1.52 – 2.03)
0.113 – 0.123
(2.87 – 3.12)
P3 0892
LT/GP 06/94 5K REV B • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7487
(408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977
© LINEAR TECHNOLOGY CORPORATION 1994
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