1
LT1086 Series
sn1086 1086ffs
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
U
■
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 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 refer-
ence/ouput voltage to 1%. Current limit is also trimmed,
minimizing the stress on both the regulator and power
source circuitry under overload conditions.
The LT1086 is pin compatible with older 3-terminal adjust-
able regulators. A minimum 10µF output capacitor is
required on these devices.
The LT1086 offers excellent line and load regulation speci-
fications 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.
1.5A Low Dropout Positive
Regulators Adjustable and
Fixed 2.85V, 3.3V, 3.6V, 5V, 12V
■
SCSI-2 Active Terminator
■
High Efficiency Linear Regulators
■
Post Regulators for Switching Supplies
■
Constant Current Regulators
■
Battery Chargers
■
Microprocessor Supply
LT1086 Dropout Voltage
OUTPUT CURRENT (A)
0
0
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
1
2
0.5 1
LT1086 • TA02
1.5
INDICATES GUARANTEED TEST POINT
–55°C ≤ T
J
≤ 150°C
0°C ≤ T
J
≤ 125°C
T
J
= –55°C
T
J
= 25°C
T
J
= 150°C
VIN ≥ 4.75V 3.3V AT 1.5A
*MAY BE OMITTED IF INPUT SUPPLY IS WELL
BYPASSED WITHIN 2" OF THE LT1086
LT1086-3.3
LT1086 • TA01
10µF*
TANTALUM 10µF
TANTALUM
IN OUT
GND
5V to 3.3V Regulator
, LTC and LT are registered trademarks of Linear Technology Corporation.
2
LT1086 Series
sn1086 1086ffs
PRECONDITIONING
UUU
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
“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
ABSOLUTE MAXIMUM RATINGS
W
WW
U
100% Thermal Shutdown Functional Test.
PACKAGE/ORDER INFORMATION
W
UU
LT1086CM
LT1086CM-3.3
LT1086CM-3.6
LT1086IM
LT1086IM-3.3
ORDER
PART NUMBER ORDER
PART NUMBER
LT1086CH
LT1086MH
ORDER
PART NUMBER ORDER
PART NUMBER
LT1086CK
LT1086CK-5
LT1086CK-12
LT1086IK
LT1086IK-5
LT1086IK-12
LT1086MK
LT1086MK-5
LT1086MK-12
θ
JA
= 150°C/W
2
1
V
IN
CASE
IS OUTPUT
ADJ (GND)*
K PACKAGE
2-LEAD TO-3 METAL CAN
BOTTOM VIEW
θ
JA
= 35°C/W
** WITH PACKAGE SOLDERED TO 0.5IN
2
COPPER AREA
OVER BACKSIDE GROUND PLANE OR INTERNAL POWER
PLANE. θ
JA
CAN VARY FROM 20°C/W TO >40°C/W
DEPENDING ON MOUNTING TECHNIQUE.
V
IN
V
OUT
ADJ
(GND)
†
M PACKAGE
3-LEAD PLASTIC DD
FRONT VIEW
TAB IS
OUTPUT
3
2
1
T PACKAGE
3-LEAD PLASTIC TO-220
FRONT VIEW
TAB IS
OUTPUT
3
2
1
V
IN
V
OUT
ADJ
(GND)
†
θ
JA
= 50°C/W
LT1086CT
LT1086CT-2.85
LT1086CT-3.3
LT1086IT
LT1086IT-5
LT1086IT-12
LT1086CT-3.6
LT1086CT-5
LT1086CT-12
θ
JA
= 30°C/W**
†For fixed versions.
BOTTOM VIEW
VIN VOUT
(CASE)
ADJ
13
2
H PACKAGE
3-LEAD TO-39 METAL CAN
(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 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.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
OBSOLETE PACKAGES
Consider the T Package for Alternate Source
3
LT1086 Series
sn1086 1086ffs
PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Voltage LT1086, LT1086H I
OUT
= 10mA, T
J
= 25°C, (V
IN
– V
OUT
) = 3V 1.238 1.250 1.262 V
(Note 3) 10mA ≤ I
OUT
≤ 1.5A, (0.5A for LT1086H), 1.5V ≤ (V
IN
– V
OUT
) ≤ 15V ●1.225 1.250 1.270 V
Output Voltage LT1086-2.85 I
OUT
= 0mA, T
J
= 25°C, V
IN
= 5V 2.82 2.85 2.88 V
(Note 3) 0V ≤ I
OUT
≤ 1.5A, 4.35V ≤ V
IN
≤ 18V ●2.79 2.85 2.91 V
LT1086-3.3 V
IN
= 5V, I
OUT
= 0mA, T
J
= 25°C 3.267 3.300 3.333 V
4.75V ≤ V
IN
≤ 18V, 0V ≤ I
OUT
≤ 1.5A ●3.235 3.300 3.365 V
LT1086-3.6 V
IN
= 5V, I
OUT
= 0mA, T
J
= 25°C 3.564 3.600 3.636 V
5V ≤ V
IN
≤ 18V, 0 ≤ I
OUT
≤ 1.5A ●3.500 3.672 V
4.75V ≤ V
IN
≤ 18V, 0 ≤ I
OUT
≤ 1A, T
J
≥ 0°C 3.500 3.672 V
V
IN
= 4.75V, I
OUT
= 1.5A, T
J
≥ 0°C 3.300 3.672 V
LT1086-5 I
OUT
= 0mA, T
J
= 25°C, V
IN
= 8V 4.950 5.000 5.050 V
0 ≤ I
OUT
≤ 1.5A, 6.5V ≤ V
IN
≤ 20V ●4.900 5.000 5.100 V
LT1086-12 I
OUT
= 0mA, T
J
= 25°C, V
IN
= 15V 11.880 12.000 12.120 V
0 ≤ I
OUT
≤ 1.5A, 13.5V ≤ V
IN
≤ 25V ●11.760 12.000 12.240 V
Line Regulation LT1086, LT1086H I
LOAD
= 10mA, 1.5V ≤ (V
IN
– V
OUT
) ≤ 15V, T
J
= 25°C 0.015 0.2 %
●0.035 0.2 %
LT1086-2.85 I
OUT
= 0mA, T
J
= 25°C, 4.35V ≤ V
IN
≤ 18V 0.3 6 mV
●0.6 6 mV
LT1086-3.3 4.5V ≤ V
IN
≤ 18V, I
OUT
= 0mA, T
J
= 25°C 0.5 10 mV
●1.0 10 mV
LT1086-3.6 4.75V ≤ V
IN
≤ 18V, I
OUT
= 0mA, T
J
= 25°C 0.5 10 mV
●1.0 10 mV
LT1086-5 I
OUT
= 0mA, T
J
= 25°C, 6.5V ≤ V
IN
≤ 20V 0.5 10 mV
●1.0 10 mV
LT1086-12 I
OUT
= 0mA, T
J
= 25°C, 13.5V ≤ V
IN
≤ 25V 1.0 25 mV
●2.0 25 mV
Load Regulation LT1086, LT1086H (V
IN
– V
OUT
) = 3V, 10mA ≤ I
OUT
≤ 1.5A, (0.5A for LT1086H)
T
J
= 25°C (Notes 2, 3) 0.1 0.3 %
●0.2 0.4 %
LT1086-2.85 V
IN
= 5V, 0 ≤ I
OUT
≤ 1.5A, T
J
= 25°C (Notes 2, 3) 3 12 mV
●620 mV
LT1086-3.3 V
IN
= 5V, 0 ≤ I
OUT
≤ 1.5A, T
J
= 25°C (Notes 2, 3) 3 15 mV
●725 mV
LT1086-3.6 V
IN
= 5.25V, 0 ≤ I
OUT
≤ 1.5A, T
J
= 25°C (Notes 2, 3) 3 15 mV
●625 mV
V
IN
= 5V, 0 ≤ I
OUT
≤ 1A, T
J
= 25°C215mV
●425 mV
LT1086-5 V
IN
= 8V, 0 ≤ I
OUT
≤ 1.5A,
T
J
= 25°C (Notes 2, 3) 5 20 mV
●10 35 mV
LT1086-12 V
IN
= 15V, 0 ≤ I
OUT
≤ 1.5A,
T
J
= 25°C (Notes 2, 3) 12 36 mV
●24 72 mV
Dropout Voltage LT1086/-2.85/-3.3/-3.6/-5/-12 ∆V
OUT
, ∆V
REF
= 1%, I
OUT
= 1.5A (Note 4) ●1.3 1.5 V
(V
IN
– V
OUT
)
LT1086H ∆V
REF
= 1%, I
OUT
= 0.5A (Note 4) ●0.95 1.25 V
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
4
LT1086 Series
sn1086 1086ffs
PARAMETER CONDITIONS MIN TYP MAX UNITS
Current Limit LT1086/-2.85/-3.3/-3.6/-5/-12 (V
IN
– V
OUT
) = 5V ●1.50 2.00 A
(V
IN
– V
OUT
) = 25V ●0.05 0.15 A
LT1086H (V
IN
– V
OUT
) = 5V ●0.50 0.700 A
(V
IN
– V
OUT
) = 25V ●0.02 0.075 A
Minimum Load Current LT1086/LT1086H (V
IN
– V
OUT
) = 25V (Note 5) ●510 mA
Quiescient Current LT1086-2.85 V
IN
≤ 18V ●510 mA
LT1086-3.3 V
IN
≤ 18V ●510 mA
LT1086-3.6 V
IN
≤ 18V ●510 mA
LT1086-5 V
IN
≤ 20V ●510 mA
LT1086-12 V
IN
≤ 25V ●510 mA
Thermal Regulation T
A
= 25°C, 30ms pulse 0.008 0.04 %/W
Ripple Rejection f = 120Hz, C
OUT
= 25µF Tantalum, I
OUT
= 1.5A, (I
OUT
= 0.5A for LT1086H)
LT1086, LT1086H C
ADJ
= 25µF, (V
IN
– V
OUT
) = 3V ●60 75 dB
LT1086-2.85 V
IN
= 6V ●60 72 dB
LT1086-3.3 V
IN
= 6.3V ●60 72 dB
LT1086-3.6 V
IN
= 6.6V ●60 72 dB
LT1086-5 V
IN
= 8V ●60 68 dB
LT1083-12 V
IN
= 15V ●54 60 dB
Adjust Pin Current LT1086, LT1086H T
J
= 25°C55µA
●120 µA
Adjust Pin Current LT1086, LT1086H 10mA ≤ I
OUT
≤ 1.5A (0.5A for LT1086H)
Change 1.5V ≤ (V
IN
– V
OUT
) ≤ 15V ●0.2 5 µA
Temperature Stability ●0.5 %
Long-Term Stability T
A
= 125°C, 1000 Hrs. 0.3 1 %
RMS Output Noise T
A
= 25°C, 10Hz = ≤ f ≤ 10kHz 0.003 %
(% of V
OUT
)
Thermal Resistance H Package: Control Circuitry/Power Transistor 15/20 °C/W
Junction-to-Case K Package: Control Circuitry/Power Transistor 1.7/4.0 °C/W
M Package: Control Circuitry/Power Transistor 1.5/4.0 °C/W
T Package: Control Circuitry/Power Transistor 1.5/4.0 °C/W
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
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.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
5
LT1086 Series
sn1086 1086ffs
TYPICAL PERFORMANCE CHARACTERISTICS
UW
LT1086 Maximum Power
Dissipation*
TEMPERATURE (°C)
–50
OUTPUT VOLTAGE CHANGE (%)
0
1
150
LT1086 • TPC04
–1
–2 050 100
2
–25 25 75 125
Temperature Stability
TEMPERATURE (°C)
–50
0
ADJUST PIN CURRENT (µA)
10
30
40
50
100
70
050 75
LT1086 • TPC05
20
80
90
60
–25 25 100 125 150
Adjust Pin Current
LT1086 Ripple Rejection
vs CurrentLT1086 Ripple Rejection LT1086-5 Ripple Rejection
OUTPUT CURRENT (A)
0
0
RIPPLE REJECTION (dB)
20
30
40
50
60
70
0.25 0.5 0.75 1.0
LT1086 • TPC08
1.25
80
90
100
10
1.5
fR = 120Hz
VRIPPLE ≤ 3VP-P
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
VOUT = 5V
CADJ = 25µF
COUT = 25µF
LT1086 Short-Circuit Current
INPUT/OUTPUT DIFFERENTIAL (V)
0
0
SHORT-CIRCUIT CURRENT (A)
0.5
1.0
1.5
2.0
2.5
510 15 20
LT1086 • TPC01
25 30
TJ = 150°C
TJ = 25°C
TJ = –55°C
GUARANTEED
OUTPUT CURRENT
CASE TEMPERATURE (°C)
*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
50
POWER (W)
15
20
130
LT1086 • TPC06
10
5
070 90 110 150
120
60 80 100 140
LT1086MK
LT1086CK
LT1086CT
FREQUENCY (Hz)
20
RIPPLE REJECTION (dB)
40
50
60
80
100
10
30
70
90
10 1k 10k 100k
LT1086 • TPC07
0100
VRIPPLE ≤ 3VP-P
(VIN – VOUT) ≥ 3V
(VIN – VOUT) ≥ VDROPOUT
VRIPPLE ≤ 0.5VP-P
CADJ = 200µF AT FREQUENCIES < 60Hz
CADJ = 25µF AT FREQUENCIES > 60Hz
IOUT = 1.5A
FREQUENCY (Hz)
20
RIPPLE REJECTION (dB)
40
50
70
80
10 1k 10k 100k
LT1086 • TPC09
0100
60
30
10
V
RIPPLE
≤ 3V
P-P
(V
IN
– V
OUT
) ≥ 3V
(V
IN
– V
OUT
) ≥ V
DROPOUT
V
RIPPLE
≤ 0.5V
P-P
I
OUT
= 1.5A
TEMPERATURE (°C)
–50
–0.20
OUTPUT VOLTAGE DEVIATION (%)
–0.15
–0.10
–0.05
0
050
100 150
LT1086 • TPC02
0.05
0.10
–25 25 75 125
∆I = 1.5A
INPUT/OUTPUT DIFFERENTIAL (V)
0
0
MINIMUM OPERATING CURRENT (mA)
1
3
4
5
10
7
10 20 25
LT1086 • TPC03
2
8
9
6
515 30 35
T
J
= 150°C
T
J
= 25°C
T
J
= –55°C
Minimum Operating Current
(Adjustable Device)LT1086 Load Regulation
6
LT1086 Series
sn1086 1086ffs
TYPICAL PERFORMANCE CHARACTERISTICS
UW
LT1086H Short-Circuit Current
LT1086 Line Transient Response
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (V)
LOAD CURRENT (A)
–0.1
0.1
0.3
LT1086 • TPC14
–0.3
1.0
–0.2
0
0.2
1.5
0.5
050 100
C
ADJ
= 0
C
ADJ
= 1µF
C
IN
= 1µF TANTALUM
C
OUT
= 10µF TANTALUM
V
OUT
= 10V
V
IN
= 13V
PRELOAD = 100mA
LT1086 Load Transient Response
LT1086H Load Regulation
LT1086H Dropout Voltage LT1086H Ripple Rejection
vs Current
OUTPUT CURRENT (A)
0
MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)
2
0.4
LT1086 • TPC16
1
00.1 0.2 0.3 0.5
–55°C ≤ T
J
≤ 150°C
0°C ≤ T
J
≤ 125°C
T
J
= –55°C
T
J
= 25°C
T
J
= 150°C
INDICATES GUARANTEED TEST POINT
TEMPERATURE (°C)
–50
–0.20
OUTPUT VOLTAGE DEVIATION (%)
–0.15
–0.10
–0.05
0
050
100 150
LT1086 • TPC17
0.05
0.10
–25 25 75 125
∆I = 0.5A
OUTPUT CURRENT (A)
0
0
RIPPLE REJECTION (dB)
20
30
40
50
60
70
0.1 0.2 0.3 0.4
LT1086 • TPC18
80
90
100
10
0.5
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
VOUT = 5V
CADJ = 25µF
COUT = 25µF
fR = 120Hz
VRIPPLE ≤ 3VP-P
LT1086-5 Ripple Rejection
vs Current
OUTPUT CURRENT (A)
0
0
RIPPLE REJECTION (dB)
20
30
40
50
60
70
0.25 0.5 0.75 1.0
LT1086 • TPC10
1.25
80
90
100
10
1.5
fR = 120Hz
VRIPPLE ≤ 3VP-P
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
VOUT = 5V
CADJ = 25µF
COUT = 25µF
LT1086-12 Ripple Rejection LT1086-12 Ripple Rejection
vs Current
OUTPUT CURRENT (A)
0
0
RIPPLE REJECTION (dB)
20
30
40
50
60
70
0.25 0.5 0.75 1.0
LT1086 • TPC12
1.25
80
90
100
10
1.5
fR = 120Hz
VRIPPLE ≤ 3VP-P
fR = 20kHz
VRIPPLE ≤ 0.5VP-P
VOUT = 5V
CADJ = 25µF
COUT = 25µF
INPUT/OUTPUT DIFFERENTIAL (V)
0
0
SHORT-CIRCUIT CURRENT (A)
0.2
0.4
0.6
0.8
1.0
1.2
5101520
LT1086 • TPC15
25
GUARANTEED
OUTPUT CURRENT
FREQUENCY (Hz)
20
RIPPLE REJECTION (dB)
40
50
70
80
10 1k 10k 100k
LT1086 • TPC11
0100
60
30
10
V
RIPPLE
≤ 3V
P-P
(V
IN
– V
OUT
) ≥ 3V
(V
IN
– V
OUT
) ≥ V
DROPOUT
V
RIPPLE
≤ 0.5V
P-P
I
OUT
= 1.5A
TIME (µs)
0
OUTPUT VOLTAGE
DEVIATION (mV)
INPUT VOLTAGE
DEVIATION (V)
–20
20
60
LT1086 • TPC13
–60
13
–40
0
40
14
12
11 100 200
C
ADJ
= 1µF
C
ADJ
= 0
V
OUT
= 10V
I
OUT
= 0.2A
C
IN
= 1µF TANTALUM
C
OUT
= 10µF TANTALUM
7
LT1086 Series
sn1086 1086ffs
TYPICAL PERFORMANCE CHARACTERISTICS
UW
CASE TEMPERATURE (°C)
*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE
50
POWER (W)
4
5
130
LT1086 • TPC20
3
2
1
070 90 110 150
120
60 80 100 140
LT1086MH
LT1086H Maximum Power
Dissipation*LT1086H Ripple Rejection
BLOCK DIAGRAM
W
–
+
THERMAL
LIMIT
V
ADJ
V
OUT
1086 • BD
V
IN
FREQUENCY (Hz)
20
RIPPLE REJECTION (dB)
40
50
60
80
100
10
30
70
90
10 1k 10k 100k
LT1086 • TPC19
0100
VRIPPLE ≤ 3VP-P
(VIN – VOUT) ≥ 3V
(VIN – VOUT) ≥ VDROPOUT
VRIPPLE ≤ 0.5VP-P
CADJ = 200µF AT FREQUENCIES < 60Hz
CADJ = 25µF AT FREQUENCIES > 60Hz
IOUT = 0.5A
8
LT1086 Series
sn1086 1086ffs
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 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. 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 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.
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
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
10µF10µF Tantalum, 50µF Aluminum None
10µF22µF Tantalum, 150µF Aluminum 20µF
Normally, capacitor values on the order of 100µF are used
in the output of many regulators to ensure good transient
APPLICATIONS INFORMATION
WUUU
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.
Another possible stability problem that can occur in mono-
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-
tance 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 over-
stressing 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 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
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
9
LT1086 Series
sn1086 1086ffs
plugging and unplugging in the system will not generate
current large enough to do any damage.
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.
the power supply may need to be cycled down to zero and
brought up again to make the output recover.
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
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 (V
OUT
/V
REF
). 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.
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 con-
stant 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 I
ADJ
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.
APPLICATIONS INFORMATION
WUUU
V
IN
V
OUT
LT1086
ADJ
IN OUT
LT1086 • AI01
C
ADJ
10µF
C
OUT
150µF
R1
D1
1N4002
(OPTIONAL)
R2
+
+
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 operat-
ing points for the regulator. With this double intersection
Figure 1. Basic Adjustable Regulator
R1 10µF
TANTALUM
R2
IN OUT
I
ADJ
50µA
ADJ
V
OUT
LT1086
V
IN
1086 • F01
V
REF
V
OUT
= V
REF
1 + + I
ADJ
R2
R2
R1
( )
+
10
LT1086 Series
sn1086 1086ffs
APPLICATIONS INFORMATION
WUUU
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
, as illustrated in Figure 2. If R1 were
connected to the load, the effective resistance between the
regulator and the load would be:
RP , RP = Parasitic Line Resistance
R2 + R1
R1
()
Thermal Considerations
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
new regulators provides a separate thermal resistance and
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.
For example, using a LT1086CK (TO-3, Commercial) and
assuming:
V
IN
(max continuous) = 9V, V
OUT
= 5V, I
OUT
= 1A,
T
A
= 75°C, θ
HEAT SINK
= 3°C/W,
θ
CASE-TO-HEAT SINK
= 0.2°C/W for T package with
thermal compound.
Power dissipation under these conditions is equal to:
P
D
= (V
IN
– V
OUT
)(I
OUT
) = 4W
Junction temperature will be equal to:
T
J
= T
A
+ P
D
(θ
HEAT SINK
+ θ
CASE-TO-HEAT SINK
+ θ
JC
)
For the Control Section:
T
J
= 75°C + 4W(3°C/W + 0.2°C/W + 1.5°C/W) = 94.6°C
95°C < 125°C = T
JMAX
(Control Section
Commercial Range)
For the Power Transistor:
T
J
= 75°C + 4W(3°C/W + 0.2°C/W + 4°C/W) = 103.8°C
103.8°C < 150°C = T
JMAX
(Power Transistor
Commercial Range)
LT1086 OUTINVIN
ADJ
RP
PARASITIC
LINE RESISTANCE
R1*
*CONNECT R1 TO CASE
CONNECT R2 TO LOAD 1086 • F02
RL
R2*
Figure 2. Connections for Best Load Regulation
Connected as shown, R
P
is not multiplied by the divider
ratio. R
P
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.
11
LT1086 Series
sn1086 1086ffs
APPLICATIONS INFORMATION
WUUU
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 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.
SCSI-2 Active Termination
TYPICAL APPLICATIONS
U
5V, 1.5A Regulator
10µF
TANTALUM
4.25V
TO 5.25V
1N5817
TERMPWR
LT1086 • TA03
10µF
TANTALUM 0.1µF
CERAMIC
18 TOTAL
110Ω
2% 110Ω
110Ω
110Ω
110Ω
2%
110Ω
2%
LT1086-2.85IN OUT
GND
+ +
V
IN
≥ 6.5V 5V AT 1.5A
*REQUIRED FOR STABILITY
LT1086
LT1086 • AI02
10µF*
TANTALUM
121Ω
1%
365Ω
1%
10µF
IN OUT
ADJ
++
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.
12
LT1086 Series
sn1086 1086ffs
TYPICAL APPLICATIONS
U
1.2V to 15V Adjustable Regulator
IN
V
IN
OUT
TTL
ADJ
1k
1k
10µF
100µF
5V
LT1086
2N3904
LT1086 • TA05
+
121Ω
1%
365Ω
1%
+
5V Regulator with Shutdown
IN OUT
ADJ
R2
5k
C1*
10µF
V
OUT†
V
IN
LT1086
LT1086 • TA04
+
C2
100µF
+
R1
121Ω
*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS
†
VOUT = 1.25V 1 + R2
R1
()
–
+
LT1086 OUTIN
V
IN
V
IN
RETURN
ADJ
R
P
(MAX DROP 300mV)
121Ω
365Ω
25Ω
10µF
5µF
100µF
LT1086 • TA09
R
L
V
OUT
5V
RETURN
25Ω
2
6
7
1
8
100pF
3
4
+
1k
LM301A
+
+
Remote Sensing
Regulator with Reference Protected High Current Lamp Driver
VIN > 11.5V 10V
LT1086-5
LT1086 • TA08
100µF
LT1029
5V
10µF
IN OUT
GND
++
Battery Charger
V
IN
V
OUT
R2
I
F
R
S
R1
LT1086
1.25V
LT1086 • TA06
R2
R1
1 +V
OUT
– 1.25
()
R2
R1
1 + – RS
I
F
=
()
1
R2
R1
1 + – RS
=
()
dIF
dVOUT
()
IN OUT
ADJ
Adjusting Output Voltage of Fixed Regulators
VIN > 12V 5V TO 10V
*OPTIONAL IMPROVES RIPPLE REJECTION
LT1086-5
LT1086 • TA07
100µF
1k
10µF
10µF*
IN OUT
GND
+ +
+
TTL OR
CMOS
15V
10k
LT1086
ADJ
INOUT
LT1086 • TA10
12V
1A
13
LT1086 Series
sn1086 1086ffs
TYPICAL APPLICATIONS
U
12V
1.5A
–12V
1.5A
LT1086
ADJ
IN OUT
LT1086 • TA12
10µF1N4002
124Ω*
1.07k*
470µF
MUR410
VIN
470µF
10µF
MUR410
FEEDBACK PATH
5V OUTPUT
(TYPICAL)
LT1086
SWITCHING
REGULATOR ADJ
IN OUT
10µF1N4002
124Ω*
1.07k*
470µF
*1% FILM RESISTORS
MUR410
10µF
+
+
+
+
+
+
+
High Efficiency Dual Supply
High Efficiency Dual Linear Supply
12V
1.5A
–12V
1.5A
124Ω*
LT1086
ADJ
IN OUT
LT1086 • TA11
1.07k*
100µF
D1
1N4002
2.4k
30k
20k*
LT1004-2.5
30.1k*
2
8
7
4
3
510k
1000µF
L1
285µH
1k
MBR360
HEAT SINK
2N6667
DARLINGTON
HEAT SINK
2N6667
DARLINGTON
10k
–
+
LT1011
4700µF
MDA201
+
–
124Ω*
LT1086
ADJ
IN OUT
1.07k*
100µF
D2
1N4002
2.4k
30k
20k*
LT1004-2.5
30.1k*
2
8
7
4
3
510k
1000µF
L1
285µH
1k
MBR360
130VAC
TO 90VAC STANCOR
P-8685
10k
–
+
LT1011
4700µF
*1% FILM RESISTORS
MDA = MOTOROLA
L1 = PULSE ENGINEERING, INC. #PE-92106
MDA201
+
–
Q1
Q2
+
+
++
+
+
14
LT1086 Series
sn1086 1086ffs
TYPICAL APPLICATIONS
U
Improving Ripple Rejection
PACKAGE DESCRIPTION
U
Battery Backed Up Regulated Supply
V
IN
5.2V LINE
5V BATTERY
LT1086-5
LT1086 • TA13
50Ω
10µF
SELECT FOR
CHARGE RATE
LT1086-5
100µF
10µF6.5V
IN OUT
GND
IN OUT
GND
+
+
+
R1
121Ω
1%
IN OUT
ADJ
R2
365Ω
1%
10µF
V
IN
≥ 6.5V LT1086 V
OUT
= 5V
LT1086 • TA14
+
C1
10µF*
150µF
+
*C1 IMPROVES RIPPLE REJECTION.
XC SHOULD BE ≈ R1 AT RIPPLE FREQUENCY
Automatic Light Control Low Dropout Negative Supply
IN
V
IN
OUT
ADJ
10µF100µF
LT1086
LT1086 • TA15
1.2k
+
IN OUT
GND
10,000µF
LT1086-12
LT1086 • TA16
100µF
V
OUT
= –12V
FLOATING INPUT
V
IN
+ +
0.016 – 0.021**
(0.406 – 0.533)
DIA
0.050
(1.270)
MAX 0.165 – 0.185
(4.191 – 4.699)
0.500
(12.700)
MIN
0.305 – 0.335
(7.747 – 8.509)
0.350 – 0.370
(8.890 – 9.398) 0.200
(5.080)
TYP
45°
H3(TO-39) 1098
0.100
(2.540)
0.100
(2.540)
0.029 – 0.045
(0.737 – 1.143)
0.028 – 0.034
(0.711 – 0.864)
REFERENCE
PLANE *
LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE
AND 0.045" BELOW THE REFERENCE PLANE
FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS 0.016 – 0.024
(0.406 – 0.610)
*
**
PIN 1
H Package
3-Lead TO-39 Metal Can
(Reference LTC DWG # 05-08-1330)
OBSOLETE PACKAGE
15
LT1086 Series
sn1086 1086ffs
OBSOLETE PACKAGE
M Package
3-Lead Plastic DD Pak
(Reference LTC DWG # 05-08-1460)
K Package
2-Lead TO-3 Metal Can
(Reference LTC DWG # 05-08-1310)
PACKAGE DESCRIPTION
U
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-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
K2 (TO-3) 1098
0.038 – 0.043
(0.965 – 1.09)
0.060 – 0.135
(1.524 – 3.429)
0.320 – 0.350
(8.13 – 8.89)
0.420 – 0.480
(10.67 – 12.19)
0.760 – 0.775
(19.30 – 19.69)
0.490 – 0.510
(12.45 – 12.95)
R
0.167 – 0.177
(4.24 – 4.49)
R
0.151 – 0.161
(3.86 – 4.09)
DIA, 2PLCS
1.177 – 1.197
(29.90 – 30.40)
0.655 – 0.675
(16.64 – 17.15)
0.067 – 0.077
(1.70 – 1.96)
0.210 – 0.220
(5.33 – 5.59)
0.425 – 0.435
(10.80 – 11.05)
M (DD3) 1098
0.050
(1.270)
BSC
0.143+0.012
–0.020
()
3.632+0.305
–0.508
0.090 – 0.110
(2.286 – 2.794) 0.013 – 0.023
(0.330 – 0.584)
0.095 – 0.115
(2.413 – 2.921)
0.004+0.008
–0.004
()
0.102+0.203
–0.102
0.050 ± 0.012
(1.270 ± 0.305)
0.059
(1.499)
TYP
0.045 – 0.055
(1.143 – 1.397)
0.165 – 0.180
(4.191 – 4.572)
0.330 – 0.370
(8.382 – 9.398)
0.060
(1.524)
TYP
0.390 – 0.415
(9.906 – 10.541)
15° TYP
0.300
(7.620)
0.075
(1.905)
0.183
(4.648)
0.060
(1.524)
0.060
(1.524)
0.256
(6.502)
BOTTOM VIEW OF DD PAK
HATCHED AREA IS SOLDER PLATED
COPPER HEAT SINK
16
LT1086 Series
sn1086 1086ffs
PART NUMBER DESCRIPTION COMMENTS
LT1129 700mA, Micropower, LDO V
IN
= 4.2V to 30V, V
OUT(MIN)
= 3.75V, I
Q
= 50µA, I
SD
= 16µA,
DD, SOT-223, S8, TO-220, TSSOP-20 Packages
LT1528 3A LDO for Microprocessor Applications V
IN
= 4V to 15V, V
OUT(MIN)
= 3.30V, I
Q
= 400µA, I
SD
= 125µA,
Fast Transient Response, DD, TO-220 Packages
LT1585 4.6A LDO , with Fast Transient Response V
IN
= 2.5V to 7V, V
OUT(MIN)
= 1.25V, I
Q
= 8mA,
Fast Transient Response, DD, TO-220 Packages
LT1761 100mA, Low Noise Micropower, LDO V
IN
= 1.8V to 20V, V
OUT(MIN)
= 1.22V, I
Q
= 20µA, I
SD
= <1µA,
Low Noise < 20µV
RMS P-P
, Stable with 1µF Ceramic Capacitors, ThinSOTTM Package
LT1762 150mA, Low Noise Micropower, LDO V
IN
= 1.8V to 20V, V
OUT(MIN)
= 1.22V, I
Q
= 25µA, I
SD
= <1µA,
Low Noise < 20µV
RMS P-P
, MSOP Package
LT1763 500mA, Low Noise Micropower, LDO V
IN
= 1.8V to 20V, V
OUT(MIN)
= 1.22V, I
Q
= 30µA, I
SD
= <1µA,
Low Noise < 20µV
RMS P-P
, S8 Package
LT1764/LT1764A 3A, Low Noise, Fast Transient Response, LDOs V
IN
= 2.7V to 20V, V
OUT(MIN)
= 1.21V, I
Q
= 1mA, I
SD
= <1µA, Low Noise
< 40µV
RMS P-P
, “A” Version Stable with Ceramic Capacitor, DD, TO-220 Packages
LT1962 300mA, Low Noise Micropower, LDO V
IN
= 1.8V to 20V, V
OUT(MIN)
= 1.22V, I
Q
= 30µA, I
SD
= <1µA,
Low Noise < 20µV
RMS P-P
, MS8 Package
LT1963/LT1963A 1.5A, Low Noise, Fast Transient Response, LDOs V
IN
= 2.1V to 20V, V
OUT(MIN)
= 1.21V, I
Q
= 1mA, I
SD
= <1µA,
Low Noise < 40µV
RMS P-P
,“A” Version Stable with Ceramic Capacitor,
DD, TO-220, SOT-223, S8 Packages
LT1964 200mA, Low Noise Micropower, Negative LDO V
IN
= –0.9V to –20V, V
OUT(MIN)
= –1.21V, I
Q
= 30µA, I
SD
= 3µA,
Low Noise < 30µV
RMS P-P
, Stable with Ceramic Capacitors, ThinSOT Package
PACKAGE DESCRIPTION
U
RELATED PARTS
0.100
(2.540)
BSC 0.028 – 0.038
(0.711 – 0.965)
T3 (TO-220) 1098
0.045 – 0.055
(1.143 – 1.397)
0.165 – 0.180
(4.191 – 4.572)
0.095 – 0.115
(2.413 – 2.921)
0.013 – 0.023
(0.330 – 0.584)
0.520 – 0.570
(13.208 – 14.478)
0.980 – 1.070
(24.892 – 27.178)
0.218 – 0.252
(5.537 – 6.401)
0.050
(1.270)
TYP
0.147 – 0.155
(3.734 – 3.937)
DIA
0.390 – 0.415
(9.906 – 10.541)
0.330 – 0.370
(8.382 – 9.398)
0.460 – 0.500
(11.684 – 12.700)
0.570 – 0.620
(14.478 – 15.748)
0.230 – 0.270
(5.842 – 6.858)
© LINEAR TECHNOLOGY CORPORATION 1988
LT/TP 0703 1K REV F • PRINTED IN USA
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900
●
FAX: (408) 434-0507
●
www.linear.com
T Package
3-Lead Plastic TO-220
(Reference LTC DWG # 05-08-1420)
ThinSOT is a trademark of Linear Technology Corporation.
