Datasheet LT1086MK-5, LT1086MK-12, LT1086MK, LT1086MH, LT1086CH Datasheet (Linear Technology)

FEATURES

■

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

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APPLICATIONS

LT1086 Series

1.5A Low Dropout Positive

Regulators Adjustable and

Fixed 2.85V, 3.3V, 3.6V, 5V, 12V

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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-to­output differential and the dropout voltage is fully speci­fied as a function of load current. Dropout is guaranteed at
a maximum of 1.5V at maximum output current, decreas­ing at lower load currents. On-chip trimming adjusts the
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

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TYPICAL APPLICATION

5V to 3.3V Regulator

V

≥ 4.75V 3.3V AT 1.5A

IN

10µF*
TANTALUM

LT1086-3.3

IN OUT

GND

LT1086 • TA01

10µF
TANTALUM

The LT1086 is pin compatible with older 3-terminal adjust­able regulators. A 10µF output capacitor is required on
these new devices; however, this is usually included in
most regulator designs.

A 2.85V output version is offered for SCSI-2 active termi­nation. For surface mount applications see the LT1117-

2.85 data sheet. For high current or lower dropout require­ments see the LT1123-2.85 data sheet.

Unlike PNP regulators, where up to 10% of the output
current is wasted as quiescent current, the LT1086 quies­cent current flows into the load, increasing efficiency.

, LTC and LT are registered trademarks of Linear Technology Corporation.

LT1086 Dropout Voltage

2

INDICATES GUARANTEED TEST POINT

–55°C ≤ TJ ≤ 150°C

1

0°C ≤ T

≤ 125°C

J



= –55°C

T

J

= 25°C

T

J

= 150°C

T

J

*MAY BE OMITTED IF INPUT SUPPLY IS WELL
BYPASSED WITHIN 2" OF THE LT1086

MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)

0

0

0.5
OUTPUT CURRENT (A)

1

1.5

LT1086 • TA02

1

LT1086 Series

WW

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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

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

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PACKAGE/ORDER INFORMATION

BOTTOM VIEW

V

IN

3-LEAD TO-39 METAL CAN

2

13

H PACKAGE



θJA = 150°C/W

ADJ

V

OUT

(CASE)



ORDER

PART NUMBER

LT1086CH
LT1086MH

“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.

UUU

PRECONDITIONING

100% Thermal Shutdown Functional Test.

FRONT VIEW

3

TAB IS

OUTPUT

3-LEAD PLASTIC DD

θJA = 30°C/W**

** WITH PACKAGE SOLDERED TO 0.5IN2 COPPER AREA

OVER BACKSIDE GROUND PLANE OR INTERNAL POWER
PLANE. θ
DEPENDING ON MOUNTING TECHNIQUE.

CAN VARY FROM 20°C/W TO >40°C/W

JA



2



1

M PACKAGE

VIN

V

OUT


ADJ
(GND)*



ORDER

PART NUMBER

LT1086CM
LT1086CM-3.3
LT1086CM-3.6
LT1086IM
LT1086IM-3.3
LT1086IM-3.6

V

IN

ADJ (GND)*

2-LEAD TO-3 METAL CAN

*For fixed versions.

2

BOTTOM VIEW

2

1

K PACKAGE

θJA = 35°C/W

CASE 

IS OUTPUT

ORDER

PART NUMBER

LT1086CK
LT1086CK-5
LT1086CK-12
LT1086IK
LT1086IK-5
LT1086IK-12
LT1086MK
LT1086MK-5
LT1086MK-12

TAB IS

OUTPUT

FRONT VIEW

3

2

1

T PACKAGE

3-LEAD PLASTIC TO-220

θJA = 50°C/W

VIN

V

OUT

ADJ
(GND)*

PART NUMBER

LT1086CT



LT1086CT-2.85
LT1086CT-3.3
LT1086IT
LT1086IT-5
LT1086IT-12
LT1086CT-3.6
LT1086CT-5
LT1086CT-12

ORDER

LT1086 Series

ELECTRICAL CHARACTERISTICS

PARAMETER CONDITIONS MIN TYP MAX UNITS

Reference Voltage LT1086, LT1086H I
(Note 2) 10mA ≤ I

Output Voltage LT1086-2.85 I
(Note 2) 0V ≤ I

LT1086-3.3 VIN = 5V, I

LT1086-3.6 VIN = 5V, I

LT1086-5 I

LT1086-12 I

Line Regulation LT1086, LT1086H I

LT1086-2.85 I

LT1086-3.3 4.5V ≤ VIN ≤ 18V, I

LT1086-3.6 4.75V ≤ VIN ≤ 18V, I

LT1086-5 I

LT1086-12 I

Load Regulation LT1086, LT1086H (VIN – V

LT1086-2.85 VIN = 5V, 0 ≤ I

LT1086-3.3 VIN = 5V, 0 ≤ I

LT1086-3.6 VIN = 5.25V, 0 ≤ I

LT1086-5 VIN = 8V, 0 ≤ I

LT1086-12 VIN = 15V, 0 ≤ I

Dropout Voltage LT1086/-2.85/-3.3/-3.6/-5/-12 ∆V

– V

OUT

)

(V

IN

LT1086H ∆V

= 10mA, TJ = 25°C, (VIN – V

OUT

OUT

4.75V ≤ V

5V ≤ V

4.75V ≤ V

= 4.75V, I

V

IN

OUT

0 ≤ I

OUT

0 ≤ I

LOAD

OUT

OUT

OUT

≤ 1.5A, (0.5A for LT1086H), 1.5V ≤ (VIN – V

OUT

= 0mA, TJ = 25°C, VIN = 5V 2.82 2.85 2.88 V

≤ 1.5A, 4.35V ≤ VIN ≤ 18V ● 2.79 2.85 2.91 V

OUT

= 0mA, TJ = 25°C 3.267 3.300 3.333 V

OUT

≤ 18V, 0V ≤ I

IN

= 0mA, TJ = 25°C 3.564 3.600 3.636 V

OUT

≤ 18V, 0 ≤ I

IN

≤ 18V, 0 ≤ I

IN

OUT

OUT

≤ 1.5A ● 3.500 3.672 V

OUT

OUT

= 1.5A, TJ ≥ 0°C 3.300 3.672 V

= 0mA, TJ = 25°C, VIN = 8V 4.950 5.000 5.050 V

≤ 1.5A, 6.5V ≤ VIN ≤ 20V ● 4.900 5.000 5.100 V

OUT

= 0mA, TJ = 25°C, VIN = 15V 11.880 12.000 12.120 V

≤ 1.5A, 13.5V ≤ VIN ≤ 25V ● 11.760 12.000 12.240 V

OUT

= 10mA, 1.5V ≤ (VIN – V

= 0mA, TJ = 25°C, 4.35V ≤ VIN ≤ 18V 0.3 6 mV

= 0mA, TJ = 25°C 0.5 10 mV

OUT

= 0mA, TJ = 25°C 0.5 10 mV

OUT

= 0mA, TJ = 25°C, 6.5V ≤ VIN ≤ 20V 0.5 10 mV

= 0mA, TJ = 25°C, 13.5V ≤ VIN ≤ 25V 1.0 25 mV

) = 3V, 10mA ≤ I

OUT

) = 3V 1.238 1.250 1.262 V

OUT

) ≤ 15V ● 1.225 1.250 1.270 V

OUT

≤ 1.5A ● 3.235 3.300 3.365 V

≤ 1A, TJ ≥ 0°C 3.500 3.672 V

) ≤ 15V, TJ = 25°C 0.015 0.2 %

OUT

≤ 1.5A, (0.5A for LT1086H)

OUT

● 0.035 0.2 %

● 0.6 6 mV

● 1.0 10 mV

● 1.0 10 mV

● 1.0 10 mV

● 2.0 25 mV

TJ = 25°C (Notes 1, 2) 0.1 0.3 %

● 0.2 0.4 %

≤ 1.5A, TJ = 25°C (Notes 1, 2) 3 12 mV

= 5V, 0 ≤ I

V

IN

= 1%, I

REF

OUT

≤ 1.5A, TJ = 25°C (Notes 1, 2) 3 15 mV

OUT

≤ 1.5A, TJ = 25°C (Notes 1, 2) 3 15 mV

OUT

≤ 1A, TJ = 25°C 2 15 mV

OUT

≤ 1.5A, TJ = 25°C (Notes 1, 2) 5 20 mV

OUT

≤ 1.5A, TJ = 25°C (Notes 1, 2) 12 36 mV

OUT

, ∆V

OUT

OUT

= 1%, I

REF

= 0.5A (Note 3) ● 0.95 1.25 V

= 1.5A (Note 3) ● 1.3 1.5 V

OUT

● 620 mV

● 725 mV

● 625 mV

● 425 mV

● 10 35 mV

● 24 72 mV

3

LT1086 Series

ELECTRICAL CHARACTERISTICS

PARAMETER CONDITIONS MIN TYP MAX UNITS

Current Limit LT1086/-2.85/-3.3/-3.6/-5/-12 (VIN – V

(V

IN

LT1086H (VIN – V

Minimum Load Current LT1086/LT1086H (VIN – V

(V

IN

– V

OUT

OUT

OUT

Quiescient Current LT1086-2.85 VIN ≤ 18V ● 510 mA

LT1086-3.3 V
LT1086-3.6 V
LT1086-5 V

≤ 18V ● 510 mA

IN

≤ 18V ● 510 mA

IN

≤ 20V ● 510 mA

IN

LT1086-12 VIN ≤ 25V ● 510 mA
Thermal Regulation TA = 25°C, 30ms pulse 0.008 0.04 %/W
Ripple Rejection f = 120Hz, C

LT1086, LT1086H C

LT1086-2.85 V

LT1086-3.3 V

LT1086-3.6 V

LT1086-5 V

= 25µF Tantalum, I

OUT

ADJ

= 6V ● 60 72 dB

IN

= 6.3V ● 60 72 dB

IN

= 6.6V ● 60 72 dB

IN

= 8V ● 60 68 dB

IN

= 25µF, (VIN – V

LT1083-12 VIN = 15V ● 54 60 dB
Adjust Pin Current LT1086, LT1086H TJ = 25°C55µA

Adjust Pin Current LT1086, LT1086H 10mA ≤ I
Change 1.5V ≤ (V

OUT

IN

Temperature Stability ● 0.5 %
Long Term Stability TA = 125°C, 1000 Hrs. 0.3 1 %
RMS Output Noise TA = 25°C, 10Hz = ≤ f ≤ 10kHz 0.003 %

OUT

)

(% of V
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

) = 5V ● 1.50 2.00 A

OUT

– V

) = 25V ● 0.05 0.15 A

OUT

) = 5V ● 0.50 0.700 A

) = 25V ● 0.02 0.075 A

) = 25V (Note 4) ● 510 mA

= 1.5A, (I

OUT

= 0.5A for LT1086H)

OUT

) = 3V ● 60 75 dB

OUT

●120 µA

≤ 1.5A, (0.5A for LT1086H)

– V

) ≤ 15V ● 0.2 5 µA

OUT

The ● denotes the specifications which apply over the full operating
temperature range.

Note 1: See thermal regulation specifications for changes in output voltage
due to heating effects. 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

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.

W

CASE TEMPERATURE (°C)

*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE

50

POWER (W)

15

20

130

LT1086 • TPC06

10

5

0

70

90

110

150

120

60

80

100

140

LT1086MK

LT1086CK

LT1086CT

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

5

15

30

35

TJ = 150°C

T

J

= 25°C

T

J

= –55°C

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TYPICAL PERFORMANCE CHARACTERISTICS

LT1086 Short-Circuit Current

2.5

2.0

1.5

1.0

SHORT-CIRCUIT CURRENT (A)

0.5

0

0

TJ = 150°C

GUARANTEED

OUTPUT CURRENT

10 15 20

5

INPUT/OUTPUT DIFFERENTIAL (V)

Temperature Stability

2



1



0



–1

OUTPUT VOLTAGE CHANGE (%)



–2

–25

–50

0

50

25

TEMPERATURE (°C)

TJ = 25°C

= –55°C

T

J

75

25 30

LT1086 • TPC01

100

LT1086 • TPC04

125

150

0.10

∆I = 1.5A

0.05

0

–0.05

–0.10

–0.15

OUTPUT VOLTAGE DEVIATION (%)

–0.20

–50

050

–25 25

TEMPERATURE (°C)

Adjust Pin Current

100

90
80
70
60
50
40
30

ADJUST PIN CURRENT (µA)

20
10

0

–50

–25 25

0

50

TEMPERATURE (°C)

100

75

LT1086 • TPC02

125

100

75

LT1086 • TPC05

125

LT1086 Series

Minimum Operating Current
(Adjustable Device)LT1086 Load Regulation

150

LT1086 Maximum Power
Dissipation*

150

LT1086 Ripple Rejection

100

V

≤ 3V

90
80
70
60
50
40
30

RIPPLE REJECTION (dB)

20
10

0

10 1k 10k 100k

RIPPLE

(VIN – V

OUT

C

= 200µF AT FREQUENCIES < 60Hz

ADJ

= 25µF AT FREQUENCIES > 60Hz

C

ADJ

= 1.5A

I

OUT

100

P-P

(VIN – V

) ≥ V

DROPOUT

FREQUENCY (Hz)

V

RIPPLE

OUT

≤ 0.5V

) ≥ 3V

LT1086 • TPC07

P-P

LT1086 Ripple Rejection
vs Current

100

90
80
70

60
50
40
30

RIPPLE REJECTION (dB)

V

20
10

= 5V

OUT

= 25µF

C

ADJ

= 25µF

C

OUT

0

0

0.25

fR = 120Hz
V

fR = 20kHz
V

0.5

OUTPUT CURRENT (A)

≤ 3V

RIPPLE

≤ 0.5V

RIPPLE

0.75 1.0

P-P

P-P

1.25

LT1086 • TPC08

RIPPLE REJECTION (dB)

1.5

LT1086-5 Ripple Rejection

80

70

60

50

40

30

20

10

0

10 1k 10k 100k

(V

I

OUT

– V

IN

= 1.5A

V

≤ 3V

RIPPLE

) ≥ V

OUT

DROPOUT

100

FREQUENCY (Hz)

P-P

(VIN – V

V

RIPPLE

OUT

≤ 0.5V

) ≥ 3V

LT1086 • TPC09

P-P

5

LT1086 Series

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
V

RIPPLE

≤ 0.5V

P-P

V

OUT

= 5V

C

ADJ

= 25µF

C

OUT

= 25µF

fR = 120Hz
V

RIPPLE

≤ 3V

P-P

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
V

RIPPLE

≤ 3V

P-P

fR = 20kHz
V

RIPPLE

≤ 0.5V

P-P

V

OUT

= 5V

C

ADJ

= 25µF

C

OUT

= 25µF

W

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TYPICAL PERFORMANCE CHARACTERISTICS

LT1086-5 Ripple Rejection
vs Current

100

90
80
70

60

40

RIPPLE REJECTION (dB)

fR = 120Hz

≤ 3V

V

RIPPLE

fR = 20kHz
V

50

30

20

10

RIPPLE

V

= 5V

OUT

= 25µF

C

ADJ

= 25µF

C

OUT

0

0

0.25

P-P

≤ 0.5V

P-P

0.75 1.0

0.5

OUTPUT CURRENT (A)

LT1086 Line Transient Response

60
40
20

0

–20

DEVIATION (mV)

OUTPUT VOLTAGE

–40

V

OUT

I

OUT

–60

C

IN

C

OUT

14
13
12

DEVIATION (V)

11

INPUT VOLTAGE

0

C

= 1µF

ADJ

= 10V

= 0.2A

= 1µF TANTALUM

= 10µF TANTALUM

100

TIME (µs)

LT1086-12 Ripple Rejection

LT1086-12 Ripple Rejection

1.25

LT1086 • TPC10

1.5

80

70

60

50

40

30

RIPPLE REJECTION (dB)

20

10

0

10 1k 10k 100k

I

(V

OUT

– V

IN

= 1.5A

V

≤ 3V

RIPPLE

) ≥ V

OUT

DROPOUT

100

FREQUENCY (Hz)

P-P

(VIN – V

V

RIPPLE

OUT

≤ 0.5V

) ≥ 3V

LT1086 • TPC11

P-P

LT1086 Load Transient Response

0.3

0.2

0.1
0

= 0

C

ADJ

–0.1

DEVIATION (V)

OUTPUT VOLTAGE

–0.2

–0.3

C

= 1µF

ADJ

CIN = 1µF TANTALUM

= 10µF TANTALUM

C

OUT

1.5

1.0

0.5

200

LT1086 • TPC13

0

LOAD CURRENT (A)

0

V
V
PRELOAD = 100mA


50

TIME (µs)

C

OUT
IN

ADJ

= 10V

= 13V

= 0

100

LT1086 • TPC14

vs Current

LT1086H Short-Circuit Current

1.2

1.0

0.8

0.6

0.4

SHORT-CIRCUIT CURRENT (A)

0.2

0

0

GUARANTEED

OUTPUT CURRENT

5101520

INPUT/OUTPUT DIFFERENTIAL (V)

25

LT1086 • TPC15

2

1

MINIMUM INPUT/OUTPUT DIFFERENTIAL (V)

0

6

LT1086H Dropout Voltage

INDICATES GUARANTEED TEST POINT

0

0.1
OUTPUT CURRENT (A)

–55°C ≤ TJ ≤ 150°C

0°C ≤ T

0.2

≤ 125°C

J

TJ = –55°C

T

= 25°C

J

= 150°C

T

J

0.3



0.4

LT1086 • TPC16

LT1086H Load Regulation

0.10

∆I = 0.5A

0.05

0

–0.05

–0.10

–0.15

OUTPUT VOLTAGE DEVIATION (%)

–0.20

0.5

–50

050

–25 25

TEMPERATURE (°C)

LT1086H Ripple Rejection
vs Current

100

75

125

LT1086 • TPC17

150

W

U

TYPICAL PERFORMANCE CHARACTERISTICS

100

V

≤ 3V

90
80
70
60
50
40
30

RIPPLE REJECTION (dB)

20
10

0

10 1k 10k 100k

RIPPLE

– V

(V

C

ADJ

C

ADJ

I

OUT

) ≥ V

IN

OUT

= 200µF AT FREQUENCIES < 60Hz
= 25µF AT FREQUENCIES > 60Hz

= 0.5A

100

FREQUENCY (Hz)

P-P

DROPOUT

V

RIPPLE

(VIN – V

OUT

≤ 0.5V

) ≥ 3V

LT1086 • TPC19

P-P

5

4

3

2

POWER (W)

1

0

*AS LIMITED BY MAXIMUM JUNCTION TEMPERATURE

LT1086H Maximum Power
Dissipation*LT1086H Ripple Rejection

LT1086MH

60

70

50

CASE TEMPERATURE (°C)

100

110

80

90

120

LT1086 Series

130

140

150

LT1086 • TPC20

BLOCK DIAGRAM

W

V

ADJ

THERMAL

LIMIT 



V

IN

+

–

1086 • BD

V

OUT

7

LT1086 Series

U

WUU

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, 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
150µ F 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 150µ F or 22µ F 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 22µ F tantalum or 150µ F
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.

Recommended Capacitor Values

INPUT OUTPUT ADJUSTMENT

10µF10µF Tantalum, 50µF Aluminum None
10µF22µF Tantalum, 150µF Aluminum 20µF

Normally, capacitor values on the order of 100µ F 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 1000µ F 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

8

LT1086 Series

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

( )

+

U

WUU

APPLICATIONS INFORMATION

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.

D1

1N4002

(OPTIONAL)

VIN V

LT1086

IN OUT



ADJ

+

C

ADJ

10µF

C

OUT

150µF

LT1086 • AI01

OUT

+

R1

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 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 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 13µ F if R1 = 100Ω. At 10kHz only

0.16µ F 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
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 a 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 I
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.

OUT/VREF

is very small and constant

ADJ

). For ex-

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

Figure 1. Basic Adjustable Regulator

9

LT1086 Series

U

WUU

APPLICATIONS INFORMATION

Load Regulation

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
case

not to the load

. This is illustrated in Figure 2. If R1
were connected to the load, the effective resistance be­tween the regulator and the load would be:

R2 + R1

RP , RP = Parasitic Line Resistance

()

R1

R



P

PARASITIC

IN

Figure 2. Connections for Best Load Regulation

LT1086 OUTINV

ADJ

*CONNECT R1 TO CASE
CONNECT R2 TO LOAD

LINE RESISTANCE



R1*

R2*

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.

directly

R

1086 • F02

to the

L

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 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

tion

and the

Power Transistor

. Previous regulators, with a

Control Sec-

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:

VIN(max continuous) = 9V, V
TA = 75°C, θ

θ

CASE-TO-HEAT SINK

HEAT SINK

= 3°C/W,

= 0.2°C/W for K package with

OUT

= 5V, I

OUT

= 1A,

thermal compound.

Power dissipation under these conditions is equal to:

PD = (VIN – V

OUT

)(I

OUT

) = 4W

Junction temperature will be equal to:

TJ = TA + PD (θ

HEAT 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 = T

(Control Section

JMAX

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 = T

(Power Transistor

JMAX

Commercial Range)

10

LT1086 Series

V

IN

≥ 6.5V 5V AT 1.5A

*REQUIRED FOR STABILITY

LT1086

LT1086 • AI02



10µF*
TANTALUM

121Ω
1%

365Ω
1%

10µF

IN OUT

ADJ

+

+

U

WUU

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.

U

TYPICAL APPLICATIONS

5V, 1.5A Regulator

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.

1N5817

+ +

10µF
TANTALUM

4.25V
TO 5.25V

SCSI-2 Active Termination

LT1086-2.85IN OUT

GND

TERMPWR

10µF
TANTALUM

0.1µF
CERAMIC

18 TOTAL

110Ω

2%

110Ω

2%

110Ω

2%

110Ω

110Ω

110Ω

LT1086 • TA03

11

LT1086 Series

IN

V

IN

OUT

TTL

ADJ

1k

1k

10µF

100µF

5V

LT1086

2N3904

LT1086 • TA05

+

121Ω
1%

365Ω
1%

+

TYPICAL APPLICATIONS

U

1.2V to 15V Adjustable Regulator

V

IN

IN OUT

LT1086

ADJ

+

C1*
10µF

*NEEDED IF DEVICE IS FAR FROM FILTER CAPACITORS

†

V

= 1.25V 1 +

OUT

(

R2
5k

R2

)

R1

Battery Charger

I

LT1086

IN

V

IN

R2

1 +V

– 1.25

OUT

=

I

F

dIF

()

dV

OUT

()

R1

R2

1 + – R

S

()

R1

1

=

R2

1 + – R

S

()

R1

ADJ

1.25V

R2

R

OUT

R1

LT1086 • TA06

R1
121Ω



F

S

5V Regulator with Shutdown

†

V

OUT

+

C2
100µF

LT1086 • TA04

Adjusting Output Voltage of Fixed Regulators

> 12V 5V TO 10V

V

OUT

V

IN

+ +

IN OUT

LT1086-5

10µF

10µF*

*OPTIONAL IMPROVES RIPPLE REJECTION

GND

+

1k

100µF

LT1086 • TA07

Regulator with Reference Protected High Current Lamp Driver

> 11.5V 10V

V

IN

10µF

LT1086-5

IN OUT

GND

5V

LT1029

++

100µF

LT1086 • TA08

TTL OR

CMOS

10k

LT1086

ADJ

INOUT



15V

12V

1A

LT1086 • TA10

Remote Sensing

R



P

V

IN

+

RETURN

10µF

LT1086 OUTIN



ADJ

100µF

25Ω

121Ω

365Ω

(MAX DROP 300mV)

+

V

IN

7

6

LM301A

1

100pF

2

–

1k

3

+

8

5µF

4

+

25Ω

V
5V

R

L

RETURN

LT1086 • TA09

OUT

12

U

TYPICAL APPLICATIONS

HEAT SINK

2N6667

DARLINGTON

+

MDA201

–

MBR360

Q1

10k

+

4700µF

High Efficiency Dual Linear Supply

L1

285µH

1000µF

++

1k

510k

8

7

LT1011

4

2.4k

2

+

3

–

LT1086

IN OUT

30k

20k*



ADJ

LT1004-2.5

30.1k*

LT1086 Series

12V

124Ω*

+

100µF

1.07k*

1.5A

D1
1N4002

130VAC

TO 90VAC

STANCOR
P-8685

DARLINGTON

HEAT SINK

2N6667

Q2

+

MDA201

+

–

*1% FILM RESISTORS
MDA = MOTOROLA
L1 = PULSE ENGINEERING, INC. #PE-92106

MBR360

10k

4700µF

1k

FEEDBACK PATH

L1

285µH

1000µF

7

510k

8

LT1011

4

2.4k

30k

2

+

3

–

IN OUT

High Efficiency Dual Supply

MUR410

5V OUTPUT
(TYPICAL)

+

470µF

LT1086

ADJ

LT1004-2.5

20k*



30.1k*

124Ω*

1.07k*

+

100µF

LT1086 • TA11

D2
1N4002

–12V

1.5A

V

IN

SWITCHING
REGULATOR

*1% FILM RESISTORS

MUR410

MUR410

IN OUT

+

470µF

IN OUT

+

470µF

LT1086

ADJ

+

LT1086

ADJ

+



10µF



10µF

124Ω*

1.07k*

124Ω*

1.07k*

12V

1.5A

+

10µF

+

10µF

LT1086 • TA12

1N4002

1N4002

–12V

1.5A

13

LT1086 Series

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

IN

OUT

GND

10,000µF

LT1086-12

LT1086 • TA16

100µF

V

OUT

= –12V

FLOATING INPUT

V

IN

+ +

TYPICAL APPLICATIONS

U

V

IN

V

Battery Backed Up Regulated Supply

IN OUT

+

SELECT FOR
CHARGE RATE

+

10µF

10µF6.5V

LT1086-5

GND

IN OUT

LT1086-5

GND

Automatic Light Control Low Dropout Negative Supply

IN

IN

LT1086

+

10µF

OUT

ADJ

50Ω





1.2k

+

5.2V LINE
5V BATTERY

100µF

LT1086 • TA13

100µF

LT1086 • TA15

Improving Ripple Rejection

PACKAGE DESCRIPTION

REFERENCE

PLANE

*

14

LEAD DIAMETER IS UNCONTROLLED BETWEEN THE REFERENCE PLANE 
AND 0.045" BELOW THE REFERENCE PLANE

**

FOR SOLDER DIP LEAD FINISH, LEAD DIAMETER IS

0.350 – 0.370

(8.890 – 9.398)



0.305 – 0.335

(7.747 – 8.509)



0.050

(1.270)

MAX

0.016 – 0.019**
(0.406 – 0.483)

DIA

U

Dimensions in inches (millimeters) unless otherwise noted.

H Package

3-Lead TO-39 Metal Can

(LTC DWG # 05-08-1330)

0.200

(5.080)

TYP

PIN 1



45°

0.165 – 0.185

(4.191 – 4.699)

*

(12.700)

0.016 – 0.024

(0.406 – 0.610)



0.500 

MIN

0.029 – 0.045

(0.737 – 1.143)



0.028 – 0.034

(0.711 – 0.864)

0.100

(2.540)



0.100

(2.540)



H3(TO-39) 1197

PACKAGE DESCRIPTION

0.320 – 0.350
(8.13 – 8.89)

0.420 – 0.480

(10.67 – 12.19)

0.760 – 0.775

(19.30 – 19.69)

0.038 – 0.043

(0.965 – 1.09)

U

Dimensions in inches (millimeters) unless otherwise noted.

K Package

2-Lead TO-3 Metal Can

(LTC DWG # 05-08-1310)

1.177 – 1.197

(29.90 – 30.40)

0.210 – 0.220
(5.33 – 5.59)





0.067 – 0.077
(1.70 – 1.96)



0.495 – 0.525

(12.57 – 13.34)

0.060 – 0.135

(1.524 – 3.429)

0.425 – 0.435

(10.80 – 11.05)

LT1086 Series

0.655 – 0.675

(16.64 – 17.15)



0.151 – 0.161
(3.86 – 4.09)

DIA, 2PLCS

0.167 – 0.177
(4.24 – 4.49)

R

R



K2 (TO-3) 0695

0.256

(6.502)

0.060

(1.524)

0.300

(7.620)

BOTTOM VIEW OF DD PAK

HATCHED AREA IS SOLDER PLATED

COPPER HEAT SINK

0.060

(1.524)

0.075

(1.905)

0.183

(4.648)

M Package

3-Lead Plastic DD Pak

(LTC DWG # 05-08-1460)

0.060

(1.524)

TYP

0.330 – 0.370

(8.382 – 9.398)

+0.012

0.143
–0.020

+0.305

3.632

()

–0.508

0.050 

(1.270)

TYP

0.390 – 0.415

(9.906 – 10.541)

15° TYP

0.090 – 0.110

(2.286 – 2.794)

0.165 – 0.180

(4.191 – 4.572)

0.059

(1.499)

TYP

0.013 – 0.023

(0.330 – 0.584)

0.045 – 0.055

(1.143 – 1.397)

+0.008

0.004
–0.004

+0.203

0.102

()

–0.102

0.095 – 0.115

(2.413 – 2.921)

0.050 ± 0.012

(1.270 ± 0.305)

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 represen­tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

15

LT1086 Series

PACKAGE DESCRIPTION

U

Dimensions in inches (millimeters) unless otherwise noted.

T Package

3-Lead Plastic TO-220

(LTC DWG # 05-08-1420)

0.980 – 1.070

(24.892 – 27.178)

RELATED PARTS

0.390 – 0.415

(9.906 – 10.541)

0.460 – 0.500

(11.684 – 12.700)

0.520 – 0.570

(13.208 – 14.478)

0.090 – 0.110

(2.286 – 2.794)

0.028 – 0.038

(0.711 – 0.965)

0.147 – 0.155

(3.734 – 3.937)

0.230 – 0.270

(5.842 – 6.858)

(14.478 – 15.748)

0.330 – 0.370

(8.382 – 9.398)

0.218 – 0.252

(5.537 – 6.401)

0.050

(1.270)

TYP

DIA

0.570 – 0.620

0.165 – 0.180

(4.191 – 4.572)

0.013 – 0.023

(0.330 – 0.584)

0.045 – 0.055

(1.143 – 1.397)

0.095 – 0.115

(2.413 – 2.921)

T3 (TO-220) 1197

PART NUMBER DESCRIPTION COMMENTS

LT1528 3A Low Dropout Regulator 0.55V Dropout for 5V to 4V Regulation
LT1587 3A Low Dropout Regulator Fast Transient Response Reduces Decoupling Capacitance

1086fe LT/GP 0398 2K REV E • PRINTED IN USA

© LINEAR TECHNOLOGY CORPORATION 1988

16

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417 ● [phone]
FAX: [phone]

●

TELEX: 499-3977 ● www.linear-tech.com