LT1086 Series
1.5A Low Dropout Positive
Regulators Adjustable and
Fixed 2.85V, 3.3V, 3.6V, 5V, 12V
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FEATURES
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DESCRIPTIO
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
Line Regulation: 0.015%
Load Regulation: 0.1%
100% Thermal Limit Functional Test
Ripple Rejection >75dB
Available in 3-Pin TO-220 and 3-Pin DD Packages
The LT1086 is pin compatible with older 3-terminal adjustable regulators. A minimum 10µF output capacitor is
required on these devices.
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APPLICATIO S
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The LT ®1086 is designed to provide up to 1.5A output
current. 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 several operating points up to a maximum
of 1.5V at maximum output current. Dropout decreases 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.
SCSI-2 Active Terminator
High Efficiency Linear Regulators
Post Regulators for Switching Supplies
Constant Current Regulators
Battery Chargers
Microprocessor Supply
The LT1086 offers excellent line and load regulation specifications and ripple rejection exceeds 75dB even at the
maximum load current of 1.5A. The LT1086 is floating
architecture with a composite NPN output stage. All of the
quiescent current and the drive current for the output
stage flows to the load increasing efficiency.
The LT1086 is available in a 3-pin TO-220 package and a
space-saving surface mountable 3-pin DD package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
5V to 3.3V Regulator
VIN ≥ 4.75V
IN
LT1086-3.3 OUT
3.3V AT 1.5A
GND
10µF*
TANTALUM
10µF
TANTALUM
LT1086 • TA01
*MAY BE OMITTED IF INPUT SUPPLY IS WELL
BYPASSED WITHIN 2" OF THE LT1086
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
LT1086 Dropout Voltage
2
INDICATES GUARANTEED TEST POINT
–55°C ≤ TJ ≤ 150°C
0°C ≤ TJ ≤ 125°C
1
TJ = – 55°C
TJ = 25°C
TJ = 150°C
0
0
1
0.5
OUTPUT CURRENT (A)
1.5
LT1086 • TA02
sn1086 1086ffs
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LT1086 Series
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ABSOLUTE MAXIMUM RATINGS (Note 1)
“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
* Although the device’s maximum operating voltage is limited, (18V for a
2.85V device, 20V for a 5V device, and 25V for adjustable and12V 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.
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Power Dissipation ............................... Internally Limited
Input Voltage* ......................................................... 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
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
PRECONDITIONING
100% Thermal Shutdown Functional Test.
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PACKAGE/ORDER INFORMATION
ORDER
PART NUMBER
BOTTOM VIEW
ADJ
LT1086CH
LT1086MH
2
VIN
1
3
VOUT
(CASE)
ORDER
PART NUMBER
FRONT VIEW
TAB IS
OUTPUT
3
VIN
2
VOUT
1
ADJ
(GND)†
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
OVER BACKSIDE GROUND PLANE OR INTERNAL POWER
PLANE. θJA CAN VARY FROM 20°C/W TO > 40°C/W
DEPENDING ON MOUNTING TECHNIQUE.
θJA = 150°C/W
ORDER
PART NUMBER
ORDER
PART NUMBER
BOTTOM VIEW
CASE
IS OUTPUT
VIN
2
1
ADJ (GND)*
K PACKAGE
2-LEAD TO-3 METAL CAN
θJA = 35°C/W
LT1086CK
LT1086CK-5
LT1086CK-12
LT1086IK
LT1086IK-5
LT1086IK-12
LT1086MK
LT1086MK-5
LT1086MK-12
LT1086CM
LT1086CM-3.3
LT1086CM-3.6
LT1086IM
LT1086IM-3.3
FRONT VIEW
TAB IS
OUTPUT
3
VIN
2
VOUT
1
ADJ
(GND)†
T PACKAGE
3-LEAD PLASTIC TO-220
θJA = 50°C/W
LT1086CT
LT1086CT-2.85
LT1086CT-3.3
LT1086IT
LT1086IT-5
LT1086IT-12
LT1086CT-3.6
LT1086CT-5
LT1086CT-12
OBSOLETE PACKAGES
Consider the T Package for Alternate Source
†
For fixed versions.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
sn1086 1086ffs
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LT1086 Series
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
Reference Voltage
(Note 3)
LT1086, LT1086H
Output Voltage
(Note 3)
LT1086-2.85
LT1086-3.3
LT1086-3.6
LT1086-5
LT1086-12
Line Regulation
LT1086, LT1086H
LT1086-2.85
LT1086-3.3
LT1086-3.6
LT1086-5
LT1086-12
Load Regulation
LT1086, LT1086H
LT1086-2.85
LT1086-3.3
LT1086-3.6
MIN
TYP
MAX
UNITS
●
1.238
1.225
1.250
1.250
1.262
1.270
V
V
IOUT = 0mA, TJ = 25°C, VIN = 5V
0V ≤ IOUT ≤ 1.5A, 4.35V ≤ VIN ≤ 18V
●
2.82
2.79
2.85
2.85
2.88
2.91
V
V
VIN = 5V, IOUT = 0mA, TJ = 25°C
4.75V ≤ VIN ≤ 18V, 0V ≤ IOUT ≤ 1.5A
●
3.267
3.235
3.300
3.300
3.333
3.365
V
V
3.564
3.500
3.500
3.300
3.600
3.636
3.672
3.672
3.672
V
V
V
V
5.000
5.000
IOUT = 10mA, TJ = 25°C, (VIN – VOUT) = 3V
10mA ≤ IOUT ≤ 1.5A, (0.5A for LT1086H), 1.5V ≤ (VIN – VOUT) ≤ 15V
VIN = 5V, IOUT = 0mA, TJ = 25°C
5V ≤ VIN ≤ 18V, 0 ≤ IOUT ≤ 1.5A
4.75V ≤ VIN ≤ 18V, 0 ≤ IOUT ≤ 1A, TJ ≥ 0°C
VIN = 4.75V, IOUT = 1.5A, TJ ≥ 0°C
●
IOUT = 0mA, TJ = 25°C, VIN = 8V
0 ≤ IOUT ≤ 1.5A, 6.5V ≤ VIN ≤ 20V
●
4.950
4.900
5.050
5.100
V
V
IOUT = 0mA, TJ = 25°C, VIN = 15V
0 ≤ IOUT ≤ 1.5A, 13.5V ≤ VIN ≤ 25V
●
11.880 12.000 12.120
11.760 12.000 12.240
V
V
●
0.015
0.035
0.2
0.2
%
%
●
0.3
0.6
6
6
mV
mV
●
0.5
1.0
10
10
mV
mV
●
0.5
1.0
10
10
mV
mV
●
0.5
1.0
10
10
mV
mV
●
1.0
2.0
25
25
mV
mV
●
0.1
0.2
0.3
0.4
%
%
●
3
6
12
20
mV
mV
●
3
7
15
25
mV
mV
●
3
6
2
4
15
25
15
25
mV
mV
mV
mV
●
5
10
20
35
mV
mV
●
12
24
36
72
mV
mV
●
1.3
1.5
V
●
0.95
1.25
V
ILOAD = 10mA, 1.5V ≤ (VIN – VOUT) ≤ 15V, TJ = 25°C
IOUT = 0mA, TJ = 25°C, 4.35V ≤ VIN ≤ 18V
4.5V ≤ VIN ≤ 18V, IOUT = 0mA, TJ = 25°C
4.75V ≤ VIN ≤ 18V, IOUT = 0mA, TJ = 25°C
IOUT = 0mA, TJ = 25°C, 6.5V ≤ VIN ≤ 20V
IOUT = 0mA, TJ = 25°C, 13.5V ≤ VIN ≤ 25V
(VIN – VOUT) = 3V, 10mA ≤ IOUT ≤ 1.5A, (0.5A for LT1086H)
TJ = 25°C (Notes 2, 3)
VIN = 5V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3)
VIN = 5V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3)
VIN = 5.25V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3)
●
VIN = 5V, 0 ≤ IOUT ≤ 1A, TJ = 25°C
LT1086-5
LT1086-12
Dropout Voltage
(VIN – VOUT)
VIN = 8V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3)
VIN = 15V, 0 ≤ IOUT ≤ 1.5A, TJ = 25°C (Notes 2, 3)
LT1086/-2.85/-3.3/-3.6/-5/-12
LT1086H
∆VOUT, ∆VREF = 1%, IOUT = 1.5A (Note 4)
∆VREF = 1%, IOUT = 0.5A (Note 4)
sn1086 1086ffs
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LT1086 Series
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
PARAMETER
CONDITIONS
Current Limit
LT1086/-2.85/-3.3/-3.6/-5/-12 (VIN – VOUT) = 5V
(VIN – VOUT) = 25V
LT1086H
Minimum Load Current
Quiescient Current
Thermal Regulation
TA = 25°C, 30ms pulse
Ripple Rejection
f = 120Hz, COUT = 25µF Tantalum, IOUT = 1.5A, (IOUT = 0.5A for LT1086H)
LT1086, LT1086H
CADJ = 25µF, (VIN – VOUT) = 3V
LT1086-2.85
VIN = 6V
LT1086-3.3
VIN = 6.3V
LT1086-3.6
VIN = 6.6V
LT1086-5
VIN = 8V
LT1083-12
VIN = 15V
Adjust Pin Current
MIN
TYP
●
●
1.50
0.05
2.00
0.15
A
A
(VIN – VOUT) = 5V
(VIN – VOUT) = 25V
●
●
0.50
0.02
0.700
0.075
A
A
LT1086/LT1086H
(VIN – VOUT) = 25V (Note 5)
●
5
10
mA
LT1086-2.85
LT1086-3.3
LT1086-3.6
LT1086-5
LT1086-12
VIN ≤ 18V
VIN ≤ 18V
VIN ≤ 18V
VIN ≤ 20V
VIN ≤ 25V
●
●
●
●
●
5
5
5
5
5
10
10
10
10
10
mA
mA
mA
mA
mA
0.008
0.04
%/W
LT1086, LT1086H
●
●
●
●
●
●
TJ = 25°C
60
60
60
60
60
54
75
72
72
72
68
60
LT1086, LT1086H
10mA ≤ IOUT ≤ 1.5A (0.5A for LT1086H)
1.5V ≤ (VIN – VOUT) ≤ 15V
Temperature Stability
●
●
Long-Term Stability
TA = 125°C, 1000 Hrs.
RMS Output Noise
(% of VOUT)
TA = 25°C, 10Hz = ≤ f ≤ 10kHz
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
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. 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 3: Line and load regulation are guaranteed up to the maximum power
dissipation of 15W (3W for the LT1086H). Power dissipation is determined
0.2
120
µA
µA
5
µA
1
%
0.5
0.3
UNITS
dB
dB
dB
dB
dB
dB
55
●
Adjust Pin Current
Change
MAX
%
0.003
%
15/20
1.7/4.0
1.5/4.0
1.5/4.0
°C/W
°C/W
°C/W
°C/W
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 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: 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.
sn1086 1086ffs
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LT1086 Series
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1086 Short-Circuit Current
Minimum Operating Current
(Adjustable Device)
LT1086 Load Regulation
2.5
10
0.10
TJ = 150°C
2.0
TJ = 25°C
TJ = –55°C
1.5
1.0
0.5
0
GUARANTEED
OUTPUT CURRENT
0
25
10
15
20
5
INPUT/OUTPUT DIFFERENTIAL (V)
30
MINIMUM OPERATING CURRENT (mA)
OUTPUT VOLTAGE DEVIATION (%)
SHORT-CIRCUIT CURRENT (A)
∆I = 1.5A
0.05
0
–0.05
–0.10
–0.15
–0.20
–50 –25
0
8
7
6
TJ = 150°C
TJ = 25°C
TJ = –55°C
5
4
3
2
1
0
25 50 75 100 125 150
TEMPERATURE (°C)
LT1086 • TPC01
9
0
20
15
10
25
30
5
INPUT/OUTPUT DIFFERENTIAL (V)
LT1086 • TPC02
Temperature Stability
LT1086 • TPC03
LT1086 Maximum Power
Dissipation*
Adjust Pin Current
100
2
35
20
1
0
–1
80
LT1086MK
15
70
60
POWER (W)
ADJUST PIN CURRENT (µA)
OUTPUT VOLTAGE CHANGE (%)
90
50
40
LT1086CT
10
LT1086CK
30
5
20
10
–2
–50 –25
0
0
–50 –25
25 50 75 100 125 150
TEMPERATURE (°C)
0
50 60 70 80 90 100 110 120 130 140 150
CASE TEMPERATURE (°C)
*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1086 • TPC05
LT1086 • TPC04
LT1086 • TPC06
LT1086 Ripple Rejection
vs Current
LT1086 Ripple Rejection
100
LT1086-5 Ripple Rejection
80
100
VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P
80
RIPPLE REJECTION (dB)
60
(VIN – VOUT) ≥ VDROPOUT
50
40
30
CADJ = 200µF AT FREQUENCIES < 60Hz
CADJ = 25µF AT FREQUENCIES > 60Hz
IOUT = 1.5A
20
10
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
70
60
50
40
30
VOUT = 5V
CADJ = 25µF
COUT = 25µF
20
10
0
100
1k
10k
FREQUENCY (Hz)
100k
LT1086 • TPC07
(VIN – VOUT) ≥ 3V
60
50
(VIN – VOUT) ≥ VDROPOUT
40
30
20
10
IOUT = 1.5A
0
0
10
VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P
70
80
(VIN – VOUT) ≥ 3V
70
fR = 120Hz
VRIPPLE ≤ 3VP-P
90
RIPPLE REJECTION (dB)
90
RIPPLE REJECTION (dB)
0
25 50 75 100 125 150
TEMPERATURE (°C)
0
0.25
0.75
1.0
1.25
0.5
OUTPUT CURRENT (A)
1.5
LT1086 • TPC08
10
100
1k
10k
FREQUENCY (Hz)
100k
LT1086 • TPC09
sn1086 1086ffs
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LT1086 Series
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1086-5 Ripple Rejection
vs Current
100
80
90
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
50
40
30
VOUT = 5V
CADJ = 25µF
COUT = 25µF
20
10
90
80
60
(VIN – VOUT) ≥ 3V
50
40
(VIN – VOUT) ≥ VDROPOUT
30
20
1.25
0.75
1.0
0.5
OUTPUT CURRENT (A)
1.5
100
10
1k
10k
FREQUENCY (Hz)
LT1086 Line Transient Response
0
–20
CADJ = 0
VOUT = 10V
IOUT = 0.2A
CIN = 1µF TANTALUM
COUT = 10µF TANTALUM
12
100
TIME (µs)
0
200
0.2
CADJ = 0
0.1
0
–0.1
CADJ = 1µF
–0.2
CIN = 1µF TANTALUM
COUT = 10µF TANTALUM
VOUT = 10V
VIN = 13V
PRELOAD = 100mA
1.5
1.0
0
0.8
0.6
0.4
0.2
0
100
100
90
0.05
fR = 120Hz
VRIPPLE ≤ 3VP-P
RIPPLE REJECTION (dB)
80
0
–0.05
–0.10
70
60
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
50
40
30
VOUT = 5V
CADJ = 25µF
COUT = 25µF
20
–0.15
0
0.1
0.3
0.4
0.2
OUTPUT CURRENT (A)
0.5
LT1086 • TPC16
–0.20
–50 –25
0
25
LT1086H Ripple Rejection
vs Current
10
0
5
10
15
20
INPUT/OUTPUT DIFFERENTIAL (V)
LT1086 • TPC15
∆I = 0.5A
TJ = – 55°C
TJ = 25°C
TJ = 150°C
GUARANTEED
OUTPUT CURRENT
0
50
TIME (µs)
0
0.10
INDICATES GUARANTEED TEST POINT
OUTPUT VOLTAGE DEVIATION (%)
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
1.0
LT1086H Load Regulation
2
1.5
LT1086H Short-Circuit Current
LT1086 • TPC14
LT1086H Dropout Voltage
1
0.75
1.0
1.25
0.5
OUTPUT CURRENT (A)
LT1086 • TPC12
0.5
LT1086 • TPC13
– 55°C ≤ TJ ≤ 150°C
0°C ≤ TJ ≤ 125°C
0.25
1.2
–0.3
13
11
VOUT = 5V
CADJ = 25µF
COUT = 25µF
0
SHORT-CIRCUIT CURRENT (A)
INPUT VOLTAGE
DEVIATION (V)
OUTPUT VOLTAGE
DEVIATION (V)
CADJ = 1µF
LOAD CURRENT (A)
OUTPUT VOLTAGE
DEVIATION (mV)
60
14
30
LT1086 Load Transient Response
40
–40
40
0
100k
0.3
–60
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
50
LT1086 • TPC11
LT1086 • TPC10
20
60
10
IOUT = 1.5A
0
0.25
fR = 120Hz
VRIPPLE ≤ 3VP-P
70
20
10
0
0
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
70
60
100
VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P
70
fR = 120Hz
VRIPPLE ≤ 3VP-P
80
LT1086-12 Ripple Rejection
vs Current
LT1086-12 Ripple Rejection
25 50 75 100 125 150
TEMPERATURE (°C)
LT1086 • TPC17
0
0
0.1
0.3
0.4
0.2
OUTPUT CURRENT (A)
0.5
LT1086 • TPC18
sn1086 1086ffs
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LT1086 Series
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TYPICAL PERFORMANCE CHARACTERISTICS
LT1086H Maximum Power
Dissipation*
LT1086H Ripple Rejection
5
100
VRIPPLE ≤ 3VP-P VRIPPLE ≤ 0.5VP-P
90
(VIN – VOUT) ≥ 3V
70
4
(VIN – VOUT) ≥ VDROPOUT
60
POWER (W)
RIPPLE REJECTION (dB)
80
50
40
3
LT1086MH
2
30
CADJ = 200µF AT FREQUENCIES < 60Hz
CADJ = 25µF AT FREQUENCIES > 60Hz
IOUT = 0.5A
20
10
1
0
10
100
1k
10k
FREQUENCY (Hz)
0
100k
50 60 70 80 90 100 110 120 130 140 150
CASE TEMPERATURE (°C)
*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
LT1086 • TPC19
LT1086 • TPC20
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BLOCK DIAGRAM
VIN
+
–
THERMAL
LIMIT
1086 • BD
VADJ
VOUT
sn1086 1086ffs
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LT1086 Series
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APPLICATIONS INFORMATION
The LT1086 family of 3-terminal regulators is easy to use
and has all the protection features that are expected in high
performance voltage regulators. They are short-circuit
protected and 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.
These regulators are pin compatible with older 3-terminal
adjustable devices, 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
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. 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 LT1086. Many
different types of capacitors with widely varying characteristics 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.
When using the LT1086 the adjustment terminal can be
bypassed to improve ripple rejection. When the adjustment terminal is bypassed the requirement for an output
capacitor increases. The values of 22µF tantalum or 150µF
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. The table
below shows approximately what size capacitors are needed
to ensure stability.
Recommended Capacitor Values
INPUT
OUTPUT
ADJUSTMENT
10µF
10µF Tantalum, 50µF Aluminum
None
10µF
22µF Tantalum, 150µF Aluminum
20µF
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 capacitor further improve stability and transient
response of the LT1086 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.
Negative resistance during current limit is not unique to
the LT1086 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-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, 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.
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 overstressing the die. The internal current paths on the LT1086
adjustment pin are limited by internal resistors. Therefore,
even with capacitors on the adjustment pin, no protection
diode is needed to ensure device safety under short-circuit
conditions.
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 capacitances, 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
pin instantaneously shorted to ground, can damage occur.
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
sn1086 1086ffs
8
LT1086 Series
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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. Of course as with any IC regulator, 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
D1
1N4002
(OPTIONAL)
VIN
IN
LT1086
OUT
ADJ
+
R1
CADJ
10µF
+
VOUT
COUT
150µF
R2
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.
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
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 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 operating points for the regulator. With this double intersection
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 frequency should equal the value of R1, (normally 100Ω to
120Ω). The size of the required adjust pin capacitor is a
function of the input ripple frequency. At 120Hz the adjust
pin capacitor should be 13µF if R1 = 100Ω; at 10kHz only
0.16µF is needed.
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 example, 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.
Output Voltage
The LT1086 develops a 1.25V reference voltage between
the output and the adjust terminal (see Figure 1). By
placing resistor R1 between these two terminals, a constant current is caused to flow through R1 and down
through R2 to set the overall output voltage. Normally this
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 represents a small error and can usually be ignored. For fixed
voltage devices R1 and R2 are included in the device.
VIN
IN
LT1086
OUT
ADJ
IADJ
50µA
(
VOUT = VREF 1 + R2
R1
+
VREF
)
R1
VOUT
10µF
TANTALUM
R2
+ IADJ R2
1086 • F01
Figure 1. Basic Adjustable Regulator
sn1086 1086ffs
9
LT1086 Series
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APPLICATIONS INFORMATION
Load Regulation
Thermal Considerations
Because the LT1086 is a 3-terminal device, it is not
possible to provide true remote load sensing. Load regulation will be limited by the resistance of the wire connecting 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 connection, with the bottom of the output divider returned to the
negative side of the load. Although it may not be immediately obvious, best load regulation is obtained when the
top of the resistor divider R1 is connected directly to the
case not to the load, as illustrated in Figure 2. If R1 were
connected to the load, the effective resistance between 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 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
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 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.
(
)
RP R2 + R1 , RP = Parasitic Line Resistance
R1
RP
PARASITIC
LINE RESISTANCE
VIN
IN
LT1086
OUT
ADJ
R1*
RL
R2*
*CONNECT R1 TO CASE
CONNECT R2 TO LOAD
1086 • F02
Figure 2. Connections for Best Load Regulation
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.
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 fixed voltage devices the top of R1 is internally Kelvin
connected and the ground pin can be used for negative
side sensing.
10
For example, using a LT1086CK (TO-3, Commercial) and
assuming:
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 T package with
thermal compound.
Power dissipation under these conditions is equal to:
PD = (VIN – VOUT)(IOUT) = 4W
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 + 1.5°C/ W) = 94.6°C
95°C < 125°C = TJMAX (Control Section
Commercial Range)
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)
sn1086 1086ffs
LT1086 Series
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APPLICATIONS INFORMATION
In both cases the junction temperature is below the
maximum rating for the respective sections, ensuring
reliable operation.
Junction-to-case thermal resistance for the K and T packages 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 resistance for the H package is therefore written to reflect this.
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. In the case of the H package, mounting the
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.
U
TYPICAL APPLICATIONS
5V, 1.5A Regulator
VIN ≥ 6.5V
IN
LT1086
5V AT 1.5A
OUT
121Ω
1%
ADJ
+
+
10µF
10µF*
TANTALUM
365Ω
1%
LT1086 • AI02
*REQUIRED FOR STABILITY
SCSI-2 Active Termination
TERMPWR
1N5817
110Ω
2%
110Ω
110Ω
2%
110Ω
110Ω
2%
110Ω
IN LT1086-2.85 OUT
GND
4.25V
TO 5.25V
+
10µF
TANTALUM
+
10µF
TANTALUM
0.1µF
CERAMIC
18 TOTAL
LT1086 • TA03
sn1086 1086ffs
11
LT1086 Series
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TYPICAL APPLICATIONS
5V Regulator with Shutdown
1.2V to 15V Adjustable Regulator
VIN
IN
LT1086
VOUT†
OUT
R1
121Ω
ADJ
+
C1*
10µF
+
R2
5k
IN
VIN
LT1086
+
5V
OUT
121Ω
1%
ADJ
+
10µF
C2
100µF
100µF
1k
365Ω
1%
2N3904
TTL
1k
*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS
R2
†V
OUT = 1.25V 1 + R1
(
)
LT1086 • TA05
LT1086 • TA04
Battery Charger
LT1086
(
(
VOUT – 1.25 1 + R2
R1
(
– RS 1 + R2
R1
)
dIF
=
dVOUT
)
VOUT
VIN > 12V
)
R1
5V TO 10V
+
GND
100µF
+
1k
10µF*
LT1086 • TA06
R2
LT1086-5 OUT
10µF
LT1086 • TA07
*OPTIONAL IMPROVES RIPPLE REJECTION
1
(
– RS 1 + R2
R1
)
Regulator with Reference
VIN > 11.5V
IN
+
1.25V
ADJ
IF =
OUT
IN
VIN
Adjusting Output Voltage of Fixed Regulators
IF
RS
IN
+
LT1086-5 OUT
GND
10µF
Protected High Current Lamp Driver
+
10V
OUT
LT1086
TTL OR
CMOS
100µF
ADJ
5V
LT1029
15V
IN
12V
1A
10k
LT1086 • TA08
LT1086 • TA10
Remote Sensing
RP
(MAX DROP 300mV)
VIN
IN
LT1086
ADJ
+
10µF
VIN
7
100µF
25Ω
+
VOUT
5V
OUT
121Ω
6
–
LM301A
1
+
8
4
365Ω
2
100pF
1k
3
RL
5µF
+
25Ω
RETURN
RETURN
LT1086 • TA09
sn1086 1086ffs
12
LT1086 Series
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TYPICAL APPLICATIONS
High Efficiency Dual Linear Supply
L1
285µH
IN
MBR360
10k
1k
+
HEAT SINK
2N6667 Q1
DARLINGTON
1000µF
ADJ
30k
+
MDA201
8
4700µF
+
7
–
12V
1.5A
OUT
124Ω*
2.4k
510k
+
LT1086
LT1004-2.5
+
20k*
2
100µF
30.1k*
D1
1N4002
1.07k*
LT1011
–
3
4
L1
285µH
STANCOR
P-8685
IN
HEAT SINK
2N6667 Q2
DARLINGTON
1000µF
MBR360
10k
1k
+
130VAC
TO 90VAC
30k
8
4700µF
+
7
–
124Ω*
2.4k
+
MDA201
OUT
ADJ
510k
+
LT1086
LT1004-2.5
+
20k*
2
100µF
30.1k*
1.07k*
D2
1N4002
LT1011
–
3
4
*1% FILM RESISTORS
MDA = MOTOROLA
L1 = PULSE ENGINEERING, INC. #PE-92106
LT1086 • TA11
–12V
1.5A
High Efficiency Dual Supply
FEEDBACK PATH
MUR410
5V OUTPUT
(TYPICAL)
+
470µF
MUR410
IN
LT1086
ADJ
+
470µF
VIN
12V
1.5A
OUT
124Ω*
+
+
10µF
10µF
1N4002
10µF
1N4002
1.07k*
MUR410
IN
SWITCHING
REGULATOR
LT1086
OUT
ADJ
+
470µF
124Ω*
+
+
10µF
1.07k*
*1% FILM RESISTORS
LT1086 • TA12
–12V
1.5A
sn1086 1086ffs
13
LT1086 Series
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TYPICAL APPLICATIONS
Improving Ripple Rejection
Battery Backed Up Regulated Supply
VIN
IN
+
5.2V LINE
5V BATTERY
LT1086-5 OUT
VIN ≥ 6.5V
GND
10µF
LT1086
IN
OUT
ADJ
+
10µF
50Ω
150µF
R2
365Ω
1%
SELECT FOR
CHARGE RATE
IN
+
6.5V
LT1086-5 OUT
+
C1
10µF*
LT1086 • TA14
+
GND
10µF
VOUT = 5V
R1
121Ω
1%
*C1 IMPROVES RIPPLE REJECTION.
XC SHOULD BE ≈ R1 AT RIPPLE FREQUENCY
100µF
LT1086 • TA13
Automatic Light Control
IN
VIN
LT1086
ADJ
+
Low Dropout Negative Supply
OUT
VIN
1.2k
IN
100µF
10µF
LT1086-12 OUT
GND
+
+
100µF
10,000µF
LT1086 • TA15
VOUT = –12V
LT1086 • TA16
FLOATING INPUT
U
PACKAGE DESCRIPTION
H Package
3-Lead TO-39 Metal Can
(Reference LTC DWG # 05-08-1330)
0.350 – 0.370
(8.890 – 9.398)
0.200
(5.080)
TYP
0.305 – 0.335
(7.747 – 8.509)
0.050
(1.270)
MAX
REFERENCE
PLANE
0.165 – 0.185
(4.191 – 4.699)
PIN 1
0.029 – 0.045
(0.737 – 1.143)
*
0.100
(2.540)
0.028 – 0.034
(0.711 – 0.864)
0.016 – 0.021**
(0.406 – 0.533)
DIA
0.100
(2.540)
0.500
(12.700)
MIN
45°
H3(TO-39) 1098
*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)
OBSOLETE PACKAGE
sn1086 1086ffs
14
LT1086 Series
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PACKAGE DESCRIPTION
K Package
2-Lead TO-3 Metal Can
(Reference LTC DWG # 05-08-1310)
0.760 – 0.775
(19.30 – 19.69)
0.320 – 0.350
(8.13 – 8.89)
0.060 – 0.135
(1.524 – 3.429)
0.420 – 0.480
(10.67 – 12.19)
0.038 – 0.043
(0.965 – 1.09)
1.177 – 1.197
(29.90 – 30.40)
0.655 – 0.675
(16.64 – 17.15)
0.210 – 0.220
(5.33 – 5.59)
0.151 – 0.161
(3.86 – 4.09)
DIA, 2PLCS
0.167 – 0.177
(4.24 – 4.49)
R
0.425 – 0.435
(10.80 – 11.05)
0.067 – 0.077
(1.70 – 1.96)
0.490 – 0.510
(12.45 – 12.95)
R
K2 (TO-3) 1098
OBSOLETE PACKAGE
M Package
3-Lead Plastic DD Pak
(Reference LTC DWG # 05-08-1460)
0.256
(6.502)
0.060
(1.524)
TYP
0.060
(1.524)
0.390 – 0.415
(9.906 – 10.541)
0.165 – 0.180
(4.191 – 4.572)
15° TYP
0.060
(1.524)
0.183
(4.648)
0.059
(1.499)
TYP
0.330 – 0.370
(8.382 – 9.398)
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
(
+0.008
0.004 –0.004
+0.203
0.102 –0.102
)
0.095 – 0.115
(2.413 – 2.921)
0.075
(1.905)
0.300
(7.620)
0.045 – 0.055
(1.143 – 1.397)
(
+0.012
0.143 – 0.020
+0.305
3.632 –0.508
)
0.090 – 0.110
(2.286 – 2.794)
0.050
(1.270)
BSC
0.013 – 0.023
(0.330 – 0.584)
0.050 ± 0.012
(1.270 ± 0.305)
M (DD3) 1098
sn1086 1086ffs
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.
15
LT1086 Series
U
PACKAGE DESCRIPTION
T Package
3-Lead Plastic TO-220
(Reference LTC DWG # 05-08-1420)
0.147 – 0.155
(3.734 – 3.937)
DIA
0.390 – 0.415
(9.906 – 10.541)
0.165 – 0.180
(4.191 – 4.572)
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)
0.100
(2.540)
BSC
0.218 – 0.252
(5.537 – 6.401)
0.013 – 0.023
(0.330 – 0.584)
0.028 – 0.038
(0.711 – 0.965)
0.095 – 0.115
(2.413 – 2.921)
0.050
(1.270)
TYP
T3 (TO-220) 1098
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1129
700mA, Micropower, LDO
VIN = 4.2V to 30V, VOUT(MIN) = 3.75V, IQ = 50µA, ISD = 16µA,
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LT1528
3A LDO for Microprocessor Applications
VIN = 4V to 15V, VOUT(MIN) = 3.30V, IQ = 400µA, ISD = 125µA,
Fast Transient Response, DD, TO-220 Packages
LT1585
4.6A LDO , with Fast Transient Response
VIN = 2.5V to 7V, VOUT(MIN) = 1.25V, IQ = 8mA,
Fast Transient Response, DD, TO-220 Packages
LT1761
100mA, Low Noise Micropower, LDO
VIN = 1.8V to 20V, VOUT(MIN) = 1.22V, IQ = 20µA, ISD =
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