LT1086CT-2.85 [Linear]
1.5A Low Dropout Positive Regulators Adjustable and Fixed 2.85V, 3.3V, 3.6V, 5V, 12V; 1.5A低压差正稳压器可调和固定2.85V ， 3.3V ， 3.6V ， 5V ， 12V
| 型号： | LT1086CT-2.85 |
| 厂家： | 
Linear |
| 描述： | 1.5A Low Dropout Positive Regulators Adjustable and Fixed 2.85V, 3.3V, 3.6V, 5V, 12V |
| 文件： | 总16页 (文件大小：351K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LT1086 Series
1.5A Low Dropout Positive
Regulators Adjustable and
Fixed 2.85V, 3.3V, 3.6V, 5V, 12V
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FEATURES
DESCRIPTION
The LT®1086 is designed to provide 1.5A 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 speci-
■
3-Terminal Adjustable or Fixed
2.85V, 3.3V, 3.6V, 5V, 12V
■
Output Current of 1.5A, (0.5A for LT1086H)
■
Operates Down to 1V Dropout
■
Guaranteed Dropout Voltage at Multiple Current Levels fied as a function of load current. Dropout is guaranteed at
■
■
■
Line Regulation: 0.015%
a maximum of 1.5V at maximum output current, decreas-
ing at lower load currents. On-chip trimming adjusts the
reference/ouput voltage to 1%. Current limit is also
trimmed, minimizing the stress on both the regulator and
power source circuitry under overload conditions.
Load Regulation: 0.1%
100% Thermal Limit Functional Test
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APPLICATIONS
TheLT1086ispincompatiblewitholder3-terminaladjust-
able regulators. A 10µF output capacitor is required on
these new devices; however, this is usually included in
most regulator designs.
■
SCSI-2 Active Terminator
■
High Efficiency Linear Regulators
■
Post Regulators for Switching Supplies
Constant Current Regulators
Battery Chargers
■
■
A 2.85V output version is offered for SCSI-2 active termi-
nation. For surface mount applications see the LT1117-
2.85datasheet. Forhighcurrentorlowerdropoutrequire-
ments see the LT1123-2.85 data sheet.
■
Microprocessor Supply
Unlike PNP regulators, where up to 10% of the output
current is wasted as quiescent current, the LT1086 quies-
cent current flows into the load, increasing efficiency.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATION
LT1086 Dropout Voltage
2
5V to 3.3V Regulator
INDICATES GUARANTEED TEST POINT
–55°C ≤ T ≤ 150°C
J
0°C ≤ T ≤ 125°C
J
V
≥ 4.75V
3.3V AT 1.5A
IN LT1086-3.3 OUT
GND
IN
10µF*
10µF
TANTALUM
1
0
TANTALUM
T
T
T
= –55°C
= 25°C
= 150°C
J
J
J
LT1086 • TA01
*MAY BE OMITTED IF INPUT SUPPLY IS WELL
BYPASSED WITHIN 2" OF THE LT1086
0
0.5
1
1.5
OUTPUT CURRENT (A)
LT1086 • TA02
1
LT1086 Series
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ABSOLUTE MAXIMUM RATINGS
Power Dissipation............................... Internally Limited
Input Voltage (Note 1) ............................................. 30V
Operating Input Voltage
Adjustable Devices ........................................... 25V
2.85V Devices .................................................. 18V
3.3V, 3.6V, and 5V Devices ............................... 20V
12V Devices ...................................................... 25V
Operating Junction Temperature Range
“C” Grades
“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
Note 1: Although the device’s maximum operating voltage is limited, (18V
for a 2.85V device, 20V for a 5V device, and 25V for adjustable and
12V devices) 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 fixed
voltage devices operating at input/output voltage differentials greater than
15V, a minimum external load of 5mA is required to maintain regulation.
Control Section ............................... 0°C to 125°C
Power Transistor............................. 0°C to 150°C
“I” Grades
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Control Section .......................... –40°C to 125°C
Power Transistor........................ –40°C to 150°C
PRECONDITIONING
100% Thermal Shutdown Functional Test.
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PACKAGE/ORDER INFORMATION
FRONT VIEW
ORDER
ORDER
BOTTOM VIEW
PART NUMBER
PART NUMBER
3
2
1
V
V
IN
ADJ
TAB IS
OUTPUT
OUT
LT1086CM
LT1086CH
LT1086MH
2
ADJ
(GND)*
V
V
1
3
IN
OUT
(CASE)
LT1086CM-3.3
LT1086CM-3.6
LT1086IM
M PACKAGE
3-LEAD PLASTIC DD
θJA = 30°C/W**
H PACKAGE
3-LEAD TO-39 METAL CAN
** WITH PACKAGE SOLDERED TO 0.5IN2 COPPER AREA
OVERBACKSIDEGROUNDPLANEORINTERNALPOWER
PLANE. θJA CAN VARY FROM 20°C/W TO >40°C/W
DEPENDING ON MOUNTING TECHNIQUE.
LT1086IM-3.3
LT1086IM-3.6
θJA = 150°C/W
ORDER
PART NUMBER
ORDER
PART NUMBER
BOTTOM VIEW
CASE
IS OUTPUT
FRONT VIEW
V
IN
3
2
1
V
V
2
1
IN
LT1086CK
LT1086CT
TAB IS
OUTPUT
OUT
LT1086CK-5
LT1086CK-12
LT1086IK
LT1086CT-2.85
LT1086CT-3.3
LT1086IT
ADJ
(GND)*
ADJ (GND)*
T PACKAGE
3-LEAD PLASTIC TO-220
K PACKAGE
2-LEAD TO-3 METAL CAN
LT1086IK-5
LT1086IK-12
LT1086MK
LT1086MK-5
LT1086MK-12
LT1086IT-5
LT1086IT-12
LT1086CT-3.6
LT1086CT-5
LT1086CT-12
θJA = 50°C/W
θJA = 35°C/W
*For fixed versions.
2
LT1086 Series
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reference Voltage LT1086, LT1086H
(Note 2)
I
= 10mA, T = 25°C, (V – V ) = 3V
1.238 1.250 1.262
1.225 1.250 1.270
V
V
OUT
J
IN
OUT
10mA ≤ I
≤ 1.5A, (0.5A for LT1086H), 1.5V ≤ (V – V ) ≤ 15V
●
●
●
●
OUT
IN
OUT
Output Voltage
(Note 2)
LT1086-2.85
LT1086-3.3
LT1086-3.6
I
= 0mA, T = 25°C, V = 5V
2.82
2.79
2.85
2.85
2.88
2.91
V
V
OUT
J
IN
0V ≤ I
≤ 1.5A, 4.35V ≤ V ≤ 18V
OUT
IN
V
= 5V, I
= 0mA, T = 25°C
3.267 3.300 3.333
3.235 3.300 3.365
V
V
IN
OUT
J
4.75V ≤ V ≤ 18V, 0V ≤ I
≤ 1.5A
IN
OUT
V
= 5V, I
IN
= 0mA, T = 25°C
3.564 3.600 3.636
V
V
V
V
IN
OUT
J
5V ≤ V ≤ 18V, 0 ≤ I
4.75V ≤ V ≤ 18V, 0 ≤ I
V
≤ 1.5A
3.500
3.500
3.300
3.672
3.672
3.672
OUT
≤ 1A, T ≥ 0°C
J
= 1.5A, T ≥ 0°C
IN
OUT
= 4.75V, I
IN
OUT J
LT1086-5
I
= 0mA, T = 25°C, V = 8V
4.950 5.000 5.050
4.900 5.000 5.100
V
V
OUT
J
IN
0 ≤ I
≤ 1.5A, 6.5V ≤ V ≤ 20V
●
●
●
●
●
●
●
●
OUT
IN
LT1086-12
LT1086, LT1086H
LT1086-2.85
LT1086-3.3
LT1086-3.6
LT1086-5
I
= 0mA, T = 25°C, V = 15V
11.880 12.000 12.120
11.760 12.000 12.240
V
V
OUT
J
IN
0 ≤ I
≤ 1.5A, 13.5V ≤ V ≤ 25V
OUT
IN
Line Regulation
I
= 10mA, 1.5V ≤ (V – V ) ≤ 15V, T = 25°C
0.015
0.035
0.2
0.2
%
%
LOAD
IN
OUT
J
I
= 0mA, T = 25°C, 4.35V ≤ V ≤ 18V
0.3
0.6
6
6
mV
mV
OUT
J
IN
4.5V ≤ V ≤ 18V, I
= 0mA, T = 25°C
0.5
1.0
10
10
mV
mV
IN
OUT
J
4.75V ≤ V ≤ 18V, I
= 0mA, T = 25°C
0.5
1.0
10
10
mV
mV
IN
OUT
J
I
I
= 0mA, T = 25°C, 6.5V ≤ V ≤ 20V
0.5
1.0
10
10
mV
mV
OUT
OUT
J
IN
LT1086-12
= 0mA, T = 25°C, 13.5V ≤ V ≤ 25V
1.0
2.0
25
25
mV
mV
J
IN
Load Regulation
LT1086, LT1086H (V – V ) = 3V, 10mA ≤ I
≤ 1.5A, (0.5A for LT1086H)
OUT
IN
OUT
T = 25°C (Notes 1, 2)
J
0.1
0.2
0.3
0.4
%
%
●
●
●
LT1086-2.85
LT1086-3.3
LT1086-3.6
V
V
= 5V, 0 ≤ I
= 5V, 0 ≤ I
≤ 1.5A, T = 25°C (Notes 1, 2)
3
6
12
20
mV
mV
IN
OUT
OUT
J
≤ 1.5A, T = 25°C (Notes 1, 2)
3
7
15
25
mV
mV
IN
J
V
V
= 5.25V, 0 ≤ I
≤ 1.5A, T = 25°C (Notes 1, 2)
3
6
2
4
15
25
15
25
mV
mV
mV
mV
IN
OUT
J
●
●
= 5V, 0 ≤ I
= 8V, 0 ≤ I
≤ 1A, T = 25°C
J
IN
OUT
OUT
LT1086-5
V
V
≤ 1.5A, T = 25°C (Notes 1, 2)
5
10
20
35
mV
mV
IN
J
●
LT1086-12
= 15V, 0 ≤ I
≤ 1.5A, T = 25°C (Notes 1, 2)
12
24
36
72
mV
mV
IN
OUT
J
●
●
Dropout Voltage
LT1086/-2.85/-3.3/-3.6/-5/-12 ∆V , ∆V = 1%, I
= 1.5A (Note 3)
1.3
1.5
V
OUT
REF
OUT
(V – V
)
IN
OUT
LT1086H
∆V = 1%, I
REF
= 0.5A (Note 3)
●
0.95
1.25
V
OUT
3
LT1086 Series
ELECTRICAL CHARACTERISTICS
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Current Limit
LT1086/-2.85/-3.3/-3.6/-5/-12 (V – V ) = 5V
●
●
1.50
0.05
2.00
0.15
A
A
IN
OUT
(V – V ) = 25V
IN
OUT
LT1086H
(V – V ) = 5V
●
●
0.50
0.02
0.700
0.075
A
A
IN
OUT
(V – V ) = 25V
IN
OUT
Minimum Load Current LT1086/LT1086H
(V – V ) = 25V (Note 4)
●
5
10
mA
IN
OUT
Quiescient Current
LT1086-2.85
LT1086-3.3
LT1086-3.6
LT1086-5
V
IN
V
IN
V
IN
V
IN
V
IN
≤ 18V
●
●
●
●
●
5
5
5
5
5
10
10
10
10
10
mA
mA
mA
mA
mA
≤ 18V
≤ 18V
≤ 20V
≤ 25V
LT1086-12
Thermal Regulation
Ripple Rejection
T = 25°C, 30ms pulse
0.008
0.04
%/W
A
f = 120Hz, C
= 25µF Tantalum, I
= 1.5A, (I
= 0.5A for LT1086H)
OUT
OUT
OUT
LT1086, LT1086H
LT1086-2.85
LT1086-3.3
LT1086-3.6
LT1086-5
C
V
V
V
V
V
= 25µF, (V – V ) = 3V
●
●
●
●
●
●
60
60
60
60
60
54
75
72
72
72
68
60
dB
dB
dB
dB
dB
dB
ADJ
IN
OUT
= 6V
IN
IN
IN
IN
IN
= 6.3V
= 6.6V
= 8V
LT1083-12
= 15V
Adjust Pin Current
LT1086, LT1086H
LT1086, LT1086H
T = 25°C
55
µA
µA
J
●
120
5
Adjust Pin Current
Change
10mA ≤ I
≤ 1.5A, (0.5A for LT1086H)
OUT
1.5V ≤ (V – V ) ≤ 15V
●
●
0.2
0.5
µA
%
%
%
IN
OUT
Temperature Stability
Long Term Stability
RMS Output Noise
T = 125°C, 1000 Hrs.
A
0.3
1
T = 25°C, 10Hz = ≤ f ≤ 10kHz
A
0.003
(% of V
)
OUT
Thermal Resistance
Junction-to-Case
H Package: Control Circuitry/Power Transistor
K Package: Control Circuitry/Power Transistor
M Package: Control Circuitry/Power Transistor
T Package: Control Circuitry/Power Transistor
15/20
1.7/4.0
1.5/4.0
1.5/4.0
°C/W
°C/W
°C/W
°C/W
The
● denotes the specifications which apply over the full operating
by the input/output differential and the output current. Guaranteed
maximum power dissipation will not be available over the full input/output
range. See Short-Circuit Current curve for available output current.
Note 3: 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 4: Minimum load current is defined as the minimum output current
required to maintain regulation. At 25V input/output differential the device
is guaranteed to regulate if the output current is greater than 10mA.
temperature range.
Note 1: See thermal regulation specifications for changes in output voltage
due to heating effects. Line and load regulation are measured at a constant
junction temperature by low duty cycle pulse testing. Load regulation is
measured at the output lead ≈1/8" from the package.
Note 2: Line and load regulation are guaranteed up to the maximum power
dissipation of 15W (3W for the LT1086H). Power dissipation is determined
4
LT1086 Series
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TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Operating Current
(Adjustable Device)
LT1086 Short-Circuit Current
LT1086 Load Regulation
2.5
2.0
1.5
1.0
10
9
8
7
6
5
4
3
2
1
0
0.10
0.05
∆I = 1.5A
T = 150°C
J
T = 25°C
J
T = –55°C
J
0
–0.05
–0.10
–0.15
–0.20
T = 150°C
J
T = 25°C
J
T = –55°C
J
0.5
0
GUARANTEED
OUTPUT CURRENT
0
10
15
20
25
30
5
75 100
TEMPERATURE (°C)
–50 –25
0
25 50
125 150
0
10
15
20
25
30
35
5
INPUT/OUTPUT DIFFERENTIAL (V)
INPUT/OUTPUT DIFFERENTIAL (V)
LT1086 • TPC01
LT1086 • TPC02
LT1086 • TPC03
LT1086 Maximum Power
Dissipation*
Temperature Stability
Adjust Pin Current
100
90
80
70
60
50
40
30
20
10
0
20
15
10
5
2
1
LT1086MK
LT1086CT
LT1086CK
0
–1
0
–2
–50
50
100 125
50 60 70
80 90
100 110 120 130 140 150
CASE TEMPERATURE (°C)
*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
50 75
TEMPERATURE (°C)
–25
0
25
75
150
–50 –25
0
25
100 125 150
TEMPERATURE (°C)
LT1086 • TPC05
LT1086 • TPC04
LT1086 • TPC06
LT1086 Ripple Rejection
vs Current
LT1086-5 Ripple Rejection
LT1086 Ripple Rejection
100
90
80
70
60
50
40
30
20
10
0
80
100
90
V
≤ 3V
V
≤ 0.5V
RIPPLE
P-P RIPPLE P-P
f = 120Hz
R
V
≤ 3V
V
≤ 0.5V
P-P
RIPPLE
P-P
RIPPLE
70
60
50
40
30
20
10
0
V
≤ 3V
P-P
RIPPLE
(V – V ) ≥ 3V
IN
OUT
80
70
60
(V – V ) ≥ 3V
IN
OUT
f
= 20kHz
RIPPLE
R
V
≤ 0.5V
P-P
(V – V ) ≥ V
(V – V ) ≥ V
IN
OUT
DROPOUT
IN
OUT
DROPOUT
50
40
30
20
10
0
C
C
= 200µF AT FREQUENCIES < 60Hz
= 25µF AT FREQUENCIES > 60Hz
= 1.5A
ADJ
ADJ
OUT
V
OUT
C
ADJ
C
OUT
= 5V
= 25µF
= 25µF
I
I
= 1.5A
100
OUT
10
100
1k
10k
100k
10
1k
10k
100k
0
0.25
0.75
1.0
1.25
1.5
0.5
FREQUENCY (Hz)
FREQUENCY (Hz)
OUTPUT CURRENT (A)
LT1086 • TPC09
LT1086 • TPC07
LT1086 • TPC08
5
LT1086 Series
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1086-5 Ripple Rejection
vs Current
LT1086-12 Ripple Rejection
vs Current
LT1086-12 Ripple Rejection
80
70
60
50
40
30
20
10
0
100
90
100
90
V
≤ 3V
V
≤ 0.5V
P-P
RIPPLE
P-P RIPPLE
f
= 120Hz
RIPPLE
R
80
70
60
80
70
60
f
= 120Hz
RIPPLE
V
≤ 3V
R
P-P
(V – V ) ≥ 3V
V
≤ 3V
IN
OUT
P-P
f
V
= 20kHz
R
≤ 0.5V
P-P
RIPPLE
f
V
= 20kHz
R
50
40
50
40
≤ 0.5V
(V – V ) ≥ V
RIPPLE
P-P
IN
OUT
DROPOUT
30
20
10
0
30
20
10
0
V
C
C
= 5V
= 25µF
= 25µF
V
C
C
= 5V
= 25µF
= 25µF
OUT
ADJ
OUT
OUT
ADJ
OUT
I
= 1.5A
100
OUT
10
1k
10k
100k
0
0.25
0.75
1.0
1.25
1.5
0.5
0
0.25
0.75
1.0
1.25
1.5
0.5
FREQUENCY (Hz)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
LT1086 • TPC11
LT1086 • TPC10
LT1086 • TPC12
LT1086 Line Transient Response
LT1086 Load Transient Response
LT1086H Short-Circuit Current
0.3
0.2
0.1
0
60
40
1.2
1.0
C
ADJ
= 0
20
C
= 1µF
ADJ
0
0.8
0.6
–0.1
–0.2
–0.3
1.5
1.0
0.5
0
C
= 1µF
ADJ
–20
–40
–60
14
C
= 0
ADJ
V
= 10V
OUT
OUT
C
C
= 1µF TANTALUM
OUT
IN
I
= 0.2A
= 10µF TANTALUM
C
C
= 1µF TANTALUM
= 10µF TANTALUM
IN
OUT
0.4
0.2
0
V
= 10V
OUT
IN
V
= 13V
13
PRELOAD = 100mA
GUARANTEED
OUTPUT CURRENT
12
11
0
100
200
0
5
10
15
20
25
0
50
TIME (µs)
100
INPUT/OUTPUT DIFFERENTIAL (V)
TIME (µs)
LT1086 • TPC13
LT1086 • TPC15
LT1086 • TPC14
LT1086H Ripple Rejection
vs Current
LT1086H Dropout Voltage
LT1086H Load Regulation
2
1
0
0.10
0.05
100
90
INDICATES GUARANTEED TEST POINT
∆I = 0.5A
f
= 120Hz
RIPPLE
80
70
60
R
–55°C ≤ T ≤ 150°C
V
≤ 3V
J
P-P
0°C ≤ T ≤ 125°C
0
J
f
= 20kHz
RIPPLE
R
–0.05
–0.10
–0.15
–0.20
50
40
V
≤ 0.5V
P-P
T = –55°C
J
30
20
10
0
T = 25°C
J
T = 150°C
J
V
OUT
C
ADJ
C
OUT
= 5V
= 25µF
= 25µF
75 100
–50 –25
0
25 50
125 150
0
0.1
0.3
OUTPUT CURRENT (A)
0.4
0.5
0.2
0
0.1
0.2
0.3
0.4
0.5
TEMPERATURE (°C)
OUTPUT CURRENT (A)
LT1086 • TPC17
LT1086 • TPC18
LT1086 • TPC16
6
LT1086 Series
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1086H Maximum Power
Dissipation*
LT1086H Ripple Rejection
100
90
80
70
60
50
40
30
20
10
0
5
V
≤ 3V
V
≤ 0.5V
RIPPLE
P-P RIPPLE P-P
4
3
2
1
0
(V – V ) ≥ 3V
IN
OUT
(V – V ) ≥ V
IN
OUT
DROPOUT
LT1086MH
C
C
= 200µF AT FREQUENCIES < 60Hz
= 25µF AT FREQUENCIES > 60Hz
= 0.5A
ADJ
ADJ
OUT
I
10
100
1k
10k
100k
50 60 70 80 90 100 110 120 130 140 150
CASE TEMPERATURE (°C)
FREQUENCY (Hz)
*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1086 • TPC19
LT1086 • TPC20
W
BLOCK DIAGRAM
V
IN
+
–
THERMAL
LIMIT
1086 • BD
V
V
ADJ
OUT
7
LT1086 Series
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APPLICATIONS INFORMATION
The LT1086 family of 3-terminal regulators is easy to use
andhasalltheprotectionfeaturesthatareexpectedinhigh
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 at the sense point.
response with heavy load current changes. Output capaci-
tance can be increased without limit and larger values of
output capacitor further improve stability and transient
response of the LT1086 regulators.
Anotherpossiblestabilityproblemthatcanoccurinmono-
lithic 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 resis-
tancesinceincreasingvoltagecausescurrenttodecrease.
Negative resistance during current limit is not unique to
the LT1086 series and has been present on all power IC
regulators. Thevalueofnegativeresistanceisafunctionof
how fast the current limit is folded back as input-to-output
voltage increases. This negative resistance can react with
capacitors or inductors on the input to cause oscillation
during current limiting. Depending on the value of series
resistance,theoverallcircuitrymayendupunstable.Since
thisisasystemproblem, itisnotnecessarilyeasytosolve;
however it does not cause any problems with the IC
regulator and can usually be ignored.
These regulators are pin compatible with older 3-terminal
adjustable devices, offer lower dropout voltage and more
precise reference tolerance. Further, the reference stabil-
ity with temperature is improved over older types of
regulators. The only circuit difference between using the
LT1086 family and older regulators is that they require an
output capacitor for stability.
Stability
The circuit design used in the LT1086 family requires the
use of an output capacitor as part of the device frequency
compensation.Foralloperatingconditions,theadditionof
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 LT1086. 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 coeffi-
cient. The 150µF or 22µF values given will ensure stability.
Protection Diodes
In normal operation the LT1086 family does not need any
protection diodes. Older adjustable regulators required
protection diodes between the adjustment pin and the
output and from the output to the input to prevent over-
stressingthedie. TheinternalcurrentpathsontheLT1086
adjustmentpin are limited byinternal resistors. Therefore,
even with capacitors on the adjustment pin, no protection
diodeisneededtoensuredevicesafetyundershort-circuit
conditions.
When using the LT1086 the adjustment terminal can be
bypassed to improve ripple rejection. When the adjust-
ment terminal is bypassed the requirement for an output
capacitorincreases. Thevaluesof22µFtantalumor150µF
aluminum cover all cases of bypassing the adjustment
terminal. For fixed voltage devices or adjustable devices
without an adjust pin bypass capacitor, smaller output
capacitors can be used with equally good results and the
table below shows approximately what size capacitors are
needed to ensure stability.
Diodes between input and output are usually not needed.
The internal diode between the input and the output pins
of the LT1086 family can handle microsecond surge
currents of 10A to 20A. Even with large output capaci-
tances, it is very difficult to get those values of surge
currents in normal operation. Only with high value output
capacitors such as 1000µF to 5000µF, and with the input
pininstantaneouslyshortedtoground,candamageoccur.
A crowbar circuit at the input of the LT1086 can generate
those kinds of currents and a diode from output to input is
then recommended. Normal power supply cycling or even
Recommended Capacitor Values
INPUT
10µF
OUTPUT
ADJUSTMENT
None
10µF Tantalum, 50µF Aluminum
22µF Tantalum, 150µF Aluminum
10µF
20µF
Normally, capacitor values on the order of 100µF are used
in the output of many regulators to ensure good transient
8
LT1086 Series
U
W U U
APPLICATIONS INFORMATION
plugging and unplugging in the system will not generate
current large enough to do any damage.
the power supply may need to be cycled down to zero and
brought up again to make the output recover.
The adjustment pin can be driven on a transient basis
±25V, with respect to the output without any device
degradation. OfcourseaswithanyICregulator, exceeding
the maximum input-to-output voltage differential causes
the internal transistors to break down and none of the
protection circuitry is functional.
Ripple Rejection
For the LT1086 the typical curves for ripple rejection
reflect values for a bypassed adjust pin. This curve will be
true for all values of output voltage. For proper bypassing
and ripple rejection approaching the values shown, the
impedance of the adjust pin capacitor at the ripple fre-
quency should equal the value of R1, (normally 100Ω to
120Ω). The size of the required adjust pin capacitor is a
functionoftheinputripplefrequency. At120Hztheadjust
pin capacitor should be 13µF if R1 = 100Ω. At 10kHz only
0.16µF is needed.
D1
1N4002
(OPTIONAL)
V
V
OUT
IN
LT1086 OUT
ADJ
IN
+
C
R1
R2
OUT
150µF
+
For circuits without an adjust pin bypass capacitor the
ripple rejection will be a function of output voltage. The
output ripple will increase directly as a ratio of the output
voltage to the reference voltage (VOUT/VREF). For ex-
ample, with the output voltage equal to 5V and no adjust
pin capacitor, the output ripple will be higher by the ratio
of 5V/1.25V or four times larger. Ripple rejection will be
degraded by 12dB from the value shown on the LT1086
curve. Typical curves are provided for the 5V and 12V
devices since the adjust pin is not available.
C
ADJ
10µF
LT1086 • AI01
Overload Recovery
Like any of the IC power regulators, the LT1086 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 LT1086
protection is designed to provide some output current at
all values of input-to-output voltage up to the device
breakdown.
Output Voltage
The LT1086 develops a 1.25V reference voltage between
the output and the adjust terminal (see Figure 1). By
placing a resistor R1 between these two terminals, a
constant current is caused to flow through R1 and down
throughR2tosettheoveralloutputvoltage.Normallythis
current is chosen to be the specified minimum load
current of 10mA. Because IADJ is very small and constant
when compared with the current through R1, it repre-
sents a small error and can usually be ignored. For fixed
voltage devices R1 and R2 are included in the device.
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
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
occurwhereinremovalofanoutputshortwillnotallowthe
output voltage to recover. Older regulators such as the
7800 series also exhibited this phenomenon, so it is not
unique to the LT1086.
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 operat-
ing points for the regulator. With this double intersection
IN
LT1086 OUT
ADJ
V
V
IN
OUT
+
10µF
V
REF
R1
R2
TANTALUM
I
ADJ
50µA
R2
R1
V
OUT
= V
1 +
+ I
R2
ADJ
REF
1086 • F01
Figure 1. Basic Adjustable Regulator
9
LT1086 Series
U
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APPLICATIONS INFORMATION
Thermal Considerations
Load Regulation
Because the LT1086 is a 3-terminal device, it is not
possible to provide true remote load sensing. Load regu-
lation will be limited by the resistance of the wire connect-
ing the regulator to the load. The data sheet specification
for load regulation is measured at the bottom of the
package. Negative side sensing is a true Kelvin connec-
tion, with the bottom of the output divider returned to the
negative side of the load. Although it may not be immedi-
ately obvious, best load regulation is obtained when the
top of the resistor divider R1 is connected directly to the
case not to the load. This is illustrated in Figure 2. If R1
were connected to the load, the effective resistance be-
tween the regulator and the load would be:
The LT1086 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 rat-
ings 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, case-
to-heat sink interface and heat sink resistance itself. New
thermal resistance specifications have been developed to
more accurately reflect device temperature and ensure
safe operating temperatures. The data section for these
newregulatorsprovidesaseparatethermalresistanceand
maximum junction temperature for both the Control Sec-
tion and the Power Transistor. 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.
R2 + R1
R
, R = Parasitic Line Resistance
P
P
(
)
R1
R
P
PARASITIC
LINE RESISTANCE
V
IN
LT1086 OUT
ADJ
IN
R1*
R2*
For example, using a LT1086CK (TO-3, Commercial) and
assuming:
R
L
VIN(max continuous) = 9V, VOUT = 5V, IOUT = 1A,
TA = 75°C, θHEAT SINK = 3°C/W,
θCASE-TO-HEAT SINK = 0.2°C/W for K package with
thermal compound.
*CONNECT R1 TO CASE
CONNECT R2 TO LOAD
1086 • F02
Figure 2. Connections for Best Load Regulation
Power dissipation under these conditions is equal to:
PD = (VIN – VOUT)(IOUT) = 4W
Connected as shown RP is not multiplied by the divider
ratio. RP is about 0.004Ω per foot using 16-gauge wire.
This translates to 4mV/ft at 1A load current, so it is
important to keep the positive lead between regulator and
load as short as possible and use large wire or PC board
traces.
Junction temperature will be equal to:
TJ = TA + PD (θHEAT SINK + θ CASE-TO-HEAT SINK + θJC)
For the Control Section:
TJ = 75°C + 4W(3°C/W + 0.2°C/W + 0.7°C/W) = 95°C
95°C < 125°C = TJMAX (Control Section
Commercial Range)
Note that the resistance of the package leads for the H
package ≈0.06Ω/inch. While it is usually not possible to
connect the load directly to the package, it is possible to
connect larger wire or PC traces close to the case to avoid
voltage drops that will degrade load regulation.
For the Power Transistor:
TJ = 75°C + 4W(3°C/W + 0.2°C/W +4°C/W) = 103.8°C
103.8°C < 150°C = TJMAX (Power Transistor
Commercial Range)
For fixed voltage devices the top of R1 is internally Kelvin
connected and the ground pin can be used for negative
side sensing.
10
LT1086 Series
U
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APPLICATIONS INFORMATION
In both cases the junction temperature is below the
maximum rating for the respective sections, ensuring
reliable operation.
In all cases proper mounting is required to ensure the best
possible heat flow from the die to the heat sink. Thermal
compound at the case-to-heat sink interface is strongly
recommended. InthecaseoftheHpackage, mountingthe
device so that heat can flow out the bottom of the case will
significantly lower thermal resistance (≈ a factor of 2). If
the case of the device must be electrically 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 electrically
connected to the output.
Junction-to-case thermal resistance for the K and T pack-
ages 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. While this is also the lowest resistance
path for the H package, most available heat sinks for this
package are of the clip-on type that attach to the cap of the
package. The data sheet specification for thermal resis-
tance for the H package is therefore written to reflect this.
U
TYPICAL APPLICATIONS
5V, 1.5A Regulator
V
≥ 6.5V
5V AT 1.5A
IN
LT1086 OUT
ADJ
IN
121Ω
1%
+
+
10µF*
TANTALUM
10µF
365Ω
1%
LT1086 • AI02
*REQUIRED FOR STABILITY
SCSI-2 Active Termination
TERMPWR
110Ω
1N5817
110Ω
110Ω
2%
IN LT1086-2.85 OUT
GND
+
+
4.25V
TO 5.25V
10µF
10µF
TANTALUM
0.1µF
CERAMIC
110Ω
2%
TANTALUM
18 TOTAL
110Ω
2%
110Ω
LT1086 • TA03
11
LT1086 Series
U
TYPICAL APPLICATIONS
5V Regulator with Shutdown
1.2V to 15V Adjustable Regulator
†
V
IN
LT1086 OUT
ADJ
V
OUT
IN
LT1086
ADJ
OUT
5V
V
IN
IN
121Ω
R1
121Ω
1%
+
+
+
10µF
1k
C1*
10µF
+
C2
100µF
100µF
R2
5k
365Ω
1%
2N3904
TTL
1k
LT1086 • TA05
*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS
†
R2 )
V
= 1.25V 1 +
LT1086 • TA04
OUT
(
R1
Battery Charger
Adjusting Output Voltage of Fixed Regulators
I
F
S
R
LT1086
OUT
1.25V
V
> 12V
5V TO 10V
100µF
IN
LT1086-5 OUT
GND
V
IN
V
OUT
IN
IN
+
+
ADJ
10µF
R1
R2
R1
+
V
– 1.25 1 +
OUT
(
)
1k
10µF*
LT1086 • TA06
LT1086 • TA07
I =
F
R2
R2
– R 1 +
S
(
)
R1
*OPTIONAL IMPROVES RIPPLE REJECTION
dI
1
F
OUT
=
(
)
dV
R2
R1
– R 1 +
S
(
)
Regulator with Reference
Protected High Current Lamp Driver
V
IN
> 11.5V
10V
IN
LT1086-5 OUT
GND
OUT LT1086
ADJ
IN
15V
+
+
TTL OR
CMOS
12V
1A
100µF
10µF
5V
LT1029
10k
LT1086 • TA08
LT1086 • TA10
Remote Sensing
R
P
(MAX DROP 300mV)
V
OUT
V
IN
IN
LT1086 OUT
ADJ
5V
+
V
IN
100µF
2
3
7
–
+
25Ω
6
LM301A
1k
5µF
+
1
121Ω
R
L
10µF
8
4
+
25Ω
100pF
365Ω
RETURN
LT1086 • TA09
RETURN
12
LT1086 Series
U
TYPICAL APPLICATIONS
High Efficiency Dual Linear Supply
L1
285µH
12V
1.5A
IN
LT1086 OUT
ADJ
1000µF
MBR360
HEAT SINK
124Ω*
2N6667 Q1
2.4k
30k
DARLINGTON
10k
1k
510k
LT1004-2.5
+
+
100µF
+
8
LT1011
4
20k*
30.1k*
2
3
D1
1N4002
MDA201
4700µF
1.07k*
+
–
7
–
L1
285µH
130VAC
TO 90VAC
STANCOR
P-8685
IN
LT1086 OUT
ADJ
1000µF
MBR360
HEAT SINK
2N6667
124Ω*
Q2
2.4k
30k
DARLINGTON
10k
1k
510k
LT1004-2.5
+
+
100µF
+
8
LT1011
4
20k*
30.1k*
2
3
D2
1N4002
MDA201
4700µF
1.07k*
+
–
7
–
–12V
1.5A
*1% FILM RESISTORS
MDA = MOTOROLA
L1 = PULSE ENGINEERING, INC. #PE-92106
LT1086 • TA11
High Efficiency Dual Supply
FEEDBACK PATH
MUR410
5V OUTPUT
(TYPICAL)
+
470µF
MUR410
12V
IN
LT1086 OUT
ADJ
1.5A
124Ω*
+
+
1N4002
10µF
470µF
+
V
1.07k*
IN
10µF
MUR410
IN
LT1086 OUT
ADJ
SWITCHING
REGULATOR
124Ω*
+
+
1N4002
10µF
470µF
+
1.07k*
10µF
–12V
1.5A
*1% FILM RESISTORS
LT1086 • TA12
13
LT1086 Series
U
TYPICAL APPLICATIONS
Improving Ripple Rejection
Battery Backed Up Regulated Supply
5.2V LINE
5V BATTERY
V
IN
≥ 6.5V
IN
LT1086 OUT
R1
V
= 5V
IN
OUT
V
LT1086-5
GND
OUT
IN
+
ADJ
121Ω
10µF
+
1%
10µF
150µF
50Ω
R2
+
C1
10µF*
SELECT FOR
CHARGE RATE
365Ω
1%
LT1086 • TA14
IN
OUT
LT1086-5
GND
+
+
*C1 IMPROVES RIPPLE REJECTION.
SHOULD BE ≈ R1 AT RIPPLE FREQUENCY
100µF
6.5V
10µF
X
C
LT1086 • TA13
Automatic Light Control
Low Dropout Negative Supply
V
IN
LT1086 OUT
IN
V
IN
ADJ
1.2k
LT1086-12
GND
OUT
IN
+
100µF
10µF
+
+
100µF
= –12V
10,000µF
V
OUT
LT1086 • TA15
LT1086 • TA16
FLOATING INPUT
U
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTION
H Package
3-Lead TO-39 Metal Can
(LTC DWG # 05-08-1330)
0.350 – 0.370
(8.890 – 9.398)
0.200
(5.080)
TYP
0.100
(2.540)
0.305 – 0.335
(7.747 – 8.509)
0.050
PIN 1
(1.270)
MAX
0.165 – 0.185
(4.191 – 4.699)
0.029 – 0.045
(0.737 – 1.143)
REFERENCE
PLANE
0.100
(2.540)
*
0.028 – 0.034
(0.711 – 0.864)
H3(TO-39) 1197
0.016 – 0.019**
0.500
(12.700)
MIN
(0.406 – 0.483)
45°
DIA
*LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE
AND 0.045" BELOW THE REFERENCE PLANE
0.016 – 0.024
**FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS
(0.406 – 0.610)
14
LT1086 Series
U
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTION
K Package
2-Lead TO-3 Metal Can
(LTC DWG # 05-08-1310)
1.177 – 1.197
(29.90 – 30.40)
0.655 – 0.675
(16.64 – 17.15)
0.760 – 0.775
(19.30 – 19.69)
0.320 – 0.350
(8.13 – 8.89)
0.210 – 0.220
(5.33 – 5.59)
0.151 – 0.161
(3.86 – 4.09)
DIA, 2PLCS
0.060 – 0.135
(1.524 – 3.429)
0.167 – 0.177
(4.24 – 4.49)
R
0.425 – 0.435
(10.80 – 11.05)
0.420 – 0.480
(10.67 – 12.19)
0.067 – 0.077
(1.70 – 1.96)
0.495 – 0.525
(12.57 – 13.34)
R
K2 (TO-3) 0695
0.038 – 0.043
(0.965 – 1.09)
M Package
3-Lead Plastic DD Pak
(LTC DWG # 05-08-1460)
0.060
(1.524)
TYP
0.390 – 0.415
(9.906 – 10.541)
0.060
(1.524)
0.165 – 0.180
(4.191 – 4.572)
0.256
(6.502)
0.045 – 0.055
(1.143 – 1.397)
15° TYP
+0.008
0.004
–0.004
0.060
(1.524)
0.059
(1.499)
TYP
0.183
(4.648)
0.330 – 0.370
(8.382 – 9.398)
+0.203
–0.102
0.102
(
)
0.095 – 0.115
(2.413 – 2.921)
0.075
(1.905)
0.090 – 0.110
(2.286 – 2.794)
0.050 ± 0.012
(1.270 ± 0.305)
0.300
(7.620)
+0.012
0.143
0.013 – 0.023
(0.330 – 0.584)
–0.020
0.050
(1.270)
TYP
+0.305
3.632
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
(
)
–0.508
M (DD3) 0396
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 represen-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
15
LT1086 Series
U
Dimensions in inches (millimeters) unless otherwise noted.
PACKAGE DESCRIPTION
T Package
3-Lead Plastic TO-220
(LTC DWG # 05-08-1420)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.165 – 0.180
(4.191 – 4.572)
0.390 – 0.415
(9.906 – 10.541)
0.045 – 0.055
(1.143 – 1.397)
0.230 – 0.270
(5.842 – 6.858)
0.570 – 0.620
(14.478 – 15.748)
0.460 – 0.500
(11.684 – 12.700)
0.330 – 0.370
(8.382 – 9.398)
0.980 – 1.070
(24.892 – 27.178)
0.520 – 0.570
(13.208 – 14.478)
0.218 – 0.252
(5.537 – 6.401)
0.013 – 0.023
(0.330 – 0.584)
0.090 – 0.110
(2.286 – 2.794)
0.095 – 0.115
(2.413 – 2.921)
0.050
(1.270)
TYP
0.028 – 0.038
(0.711 – 0.965)
T3 (TO-220) 1197
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1528
3A Low Dropout Regulator
3A Low Dropout Regulator
0.55V Dropout for 5V to 4V Regulation
LT1587
Fast Transient Response Reduces Decoupling Capacitance
1086fe LT/GP 0398 2K REV E • PRINTED IN USA
16 Linear Technology Corporation
●
1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408)432-1900
●
●
FAX: (408) 434-0507 TELEX: 499-3977 www.linear-tech.com
© LINEAR TECHNOLOGY CORPORATION 1988
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