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LT3085

Adjustable 500mA Single Resistor

Low Dropout Regulator

FEATURES

DESCRIPTION

The

3085

is a 500mA low dropout linear regulator

that can be paralleled to increase output current or spread

heat on surface mounted boards. Designed as a precision

current source and voltage follower, this new regulator

finds use in many applications requiring high current,

adjustability to zero, and no heat sink. The device also

brings out the collector of the pass transistor to allow low

dropout operation—down to 275mV—when used with a

second supply.

A key feature of the LT3085 is the capability to supply

a wide output voltage range. By using a reference cur-

rent through a single resistor, the output voltage is pro-

grammed to any level between zero and 36V. The LT3085

is stable with 2.2µF of capacitance on the output, and

the IC uses small ceramic capacitors that do not require

additional ESR as is common with other regulators.

Internal protection circuitry includes current limiting

and thermal limiting. The LT3085 is offered in the 8-lead

MSOP and a low profile (0.75mm) 6-lead 2mm × 3mm

DFN package (both with an Exposed Pad for better ther-

mal characteristics).

All registered trademarks and trademarks are the property of their respective owners.

Outputs May be Paralleled for Higher Current and

Heat Spreading

Output Current: 500mA

Single Resistor Programs Output Voltage

1% Initial Accuracy of SET Pin Current

Output Adjustable to 0V

Current Limit Constant with Temperature

Low Output Noise: 40µV

RMS

(10Hz to 100kHz)

Wide Input Voltage Range: 1.2V to 36V

Low Dropout Voltage: 275mV

< 1mV Load Regulation

< 0.001%/ V Line Regulation

Minimum Load Current: 0.5mA

Stable with Minimum 2.2µF Ceramic Capacitor

Current Limit with Foldback and Overtemperature

Protected

8-Lead MSOP, and 6-Lead 2mm × 3mm DFN Packages

AEC-Q100 Qualified for Automotive Applications

APPLICATIONS

High Current All Surface Mount Supply

High Efficiency Linear Regulator

Post Regulator for Switching Supplies

Low Parts Count Variable Voltage Supply

Low Output Voltage Power Supplies

TYPICAL APPLICATION

Variable Output Voltage 500mA Supply

1.2V TO 36V

CONTROL

LT3085

N = 1676

1µF

SET

–

OUT

2.2µF

9.80

10.00

10.20

9.90

10.10

SET PIN CURRENT DISTRIBUTION (µA)

3085 TA01b

SET

OUT

= R

SET

• 10µA

3085 TA01a

Document Feedback

For more information

www.analog.com

Rev. C

LT3085

ABSOLUTE MAXIMUM RATINGS

(Note 1) All Voltages Relative to V

OUT

CONTROL

Pin Voltage ....................................40V, –0.3V

IN Pin Voltage ................................................40V, –0.3V

SET Pin Current (Note 7) ..................................... ±15mA

SET Pin Voltage (Relative to OUT) .......................... ±10V

Output Short-Circuit Duration .......................... Indefinite

Operating Junction Temperature Range (Notes 2, 10)

E, I Grade ........................................... –40°C to 125°C

MP Grade ........................................... –55°C to 125°C

Storage Temperature Range .................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec)

MS8E Package Only.......................................... 300°C

PIN CONFIGURATION

TOP VIEW

OUT 1

OUT 2

SET 3

6 IN

5 IN

4 V

CONTROL

OUT

SET

CONTROL

DCB PACKAGE

6-LEAD (2mm × 3mm) PLASTIC DFN

JMAX

= 125°C,

= 73°C/W,

= 10.6°C/W

EXPOSED PAD (PIN 7) IS OUT, MUST BE SOLDERED TO VOUT ON PCB

SEE THE APPLICATIONS INFORMATION SECTION

MS8E PACKAGE

8-LEAD PLASTIC MSOP

JMAX

= 125°C,

= 60°C/W,

= 10°C/W

EXPOSED PAD (PIN 9) IS OUT, MUST BE SOLDERED TO VOUT ON PCB

SEE THE APPLICATIONS INFORMATION SECTION

ORDER INFORMATION

LEAD FREE FINISH

LT3085EDCB#PBF

LT3085EMS8E#PBF

LT3085IDCB#PBF

LT3085IMS8E#PBF

LT3085MPMS8E#PBF

LEAD BASED FINISH

LT3085EDCB

LT3085EMS8E

LT3085IDCB

LT3085IMS8E

LT3085MPMS8E

AUTOMOTIVE PRODUCTS**

LEAD FREE FINISH

LT3085EMS8E#WPBF

LT3085IMS8E#WPBF

TAPE AND REEL

LT3085EMS8E#WTRPBF

LT3085IMS8E#WTRPBF

PART MARKING*

LTDQP

PACKAGE DESCRIPTION

8-Lead Plastic MSOP

TEMPERATURE RANGE

–40°C to 125°C

TAPE AND REEL

LT3085EDCB#TRPBF

LT3085EMS8E#TRPBF

LT3085IDCB#TRPBF

LT3085IMS8E#TRPBF

LT3085MPMS8E#TRPBF

TAPE AND REEL

LT3085EDCB#TR

LT3085EMS8E#TR

LT3085IDCB#TR

LT3085IMS8E#TR

LT3085MPMS8E#TR

PART MARKING*

LDQQ

LTDQP

LDQQ

LTDQP

LTDWQ

PART MARKING*

LDQQ

LTDQP

LDQQ

LTDQP

LTDWQ

PACKAGE DESCRIPTION

6-Lead (2mm × 3mm) Plastic DFN

8-Lead Plastic MSOP

6-Lead (2mm × 3mm) Plastic DFN

8-Lead Plastic MSOP

PACKAGE DESCRIPTION

6-Lead (2mm × 3mm) Plastic DFN

8-Lead Plastic MSOP

6-Lead (2mm × 3mm) Plastic DFN

8-Lead Plastic MSOP

TEMPERATURE RANGE

–40°C to 125°C

–55°C to 125°C

TEMPERATURE RANGE

–40°C to 125°C

–55°C to 125°C

Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

Tape and reel specifications.

Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.

**Versions

of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These

models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your

local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for

these models.

Rev. C

For more information

www.analog.com

LT3085

ELECTRICAL CHARACTERISTICS

PARAMETER

SET Pin Current

Output Offset Voltage (V

OUT

– V

SET

)

Load Regulation

Line Regulation

Minimum Load Current (Notes 3, 9)

CONTROL

Dropout Voltage (Note 4)

CONTROL

Pin Current (Note 5)

Current Limit (Note 9)

Error Amplifier RMS Output Noise (Note 6)

Ripple Rejection

CONDITIONS

SET

= 1V, V

CONTROL

= 2V, I

LOAD

= 1mA, T

= 25°C

≥ 1V, V

CONTROL

≥ 2V, 1mA ≤ I

LOAD

≤ 500mA (Note 9)

= 1V, V

CONTROL

= 2V, I

LOAD

= 1mA, T

= 25°C

≥ 1V, V

CONTROL

≥ 2V, 1mA ≤ I

LOAD

≤ 500mA (Note 9)

½I

SET

½I

LOAD

= 1mA to 500mA

½V

½I

LOAD

= 1mA to 500mA (Note 8)

½I

SET

½V

= 1V to 36V, ½V

CONTROL

= 2V to 36V, I

LOAD

= 1mA

½V

= 1V to 36V, ½V

CONTROL

= 2V to 36V, I

LOAD

= 1mA

= V

CONTROL

= 10V

= V

CONTROL

= 36V

LOAD

= 100mA

LOAD

= 500mA

LOAD

= 100mA

LOAD

= 500mA

LOAD

= 100mA

LOAD

= 500mA

= 5V, V

CONTROL

= 5V, V

SET

= 0V, V

OUT

= –0.1V

LOAD

= 500mA, 10Hz ≤ f ≤ 100kHz, C

OUT

= 10µF, C

SET

= 0.1µF

f = 120Hz, V

RIPPLE

= 0.5V

P-P

, I

LOAD

= 0.1A, C

SET

= 0.1µF, C

OUT

= 2.2µF

f=10kHz

f=1MHz

10ms Pulse

The

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

= 25°C (Note 2).

MIN

9.9

9.8

–1.5

–3

–0.1

–0.6

0.1

0.003

300

1.2

1.35

275

500

650

0.7

0.003

TYP

MAX

10.1

10.2

1.5

–1

0.5

500

1.6

150

450

UNITS

µA

nA/V

mV/V

µA

µV

RMS

%/W

Reference Current RMS Output Noise (Note 6) 10Hz ≤ f≤ 100kHz

Thermal Regulation, I

SET

Note 1:

Stresses beyond those listed under Absolute Maximum Ratings

may cause permanent damage to the device. Exposure to any Absolute

Maximum Rating condition for extended periods may affect device

reliability and lifetime.

Note 2.

Unless otherwise specified, all voltages are with respect to V

OUT

The LT3085 is tested and specified under pulse load conditions such that

≅

. The LT3085E is 100% tested at T

= 25°C. Performance of the

LT3085E over the full –40°C to 125°C operating junction temperature

range is assured by design, characterization, and correlation with

statistical process controls. The LT3085I regulators are guaranteed

over the full –40°C to 125°C operating junction temperature range. The

LT3085 (MP grade) is 100% tested and guaranteed over the –55°C to

125°C operating junction temperature range.

Note 3.

Minimum load current is equivalent to the quiescent current of

the part. Since all quiescent and drive current is delivered to the output

of the part, the minimum load current is the minimum current required to

maintain regulation.

Note 4.

For the LT3085, dropout is caused by either minimum control

voltage (V

CONTROL

) or minimum input voltage (V

). Both parameters

are specified with respect to the output voltage. The specifications

represent the minimum input-to-output differential voltage required to

maintain regulation.

Note 5.

The V

CONTROL

pin current is the drive current required for the

output transistor. This current will track output current with roughly a 1:60

ratio. The minimum value is equal to the quiescent current of the device.

Note 6.

Output noise is lowered by adding a small capacitor across the

voltage setting resistor. Adding this capacitor bypasses the voltage setting

resistor shot noise and reference current noise; output noise is then equal

to error amplifier noise (see Applications Information section).

Note 7.

The SET pin is clamped to the output with diodes through 1k

resistors. These resistors and diodes will only carry current under

transient overloads.

Note 8.

Load regulation is Kelvin sensed at the package.

Note 9.

Current limit includes foldback protection circuitry. Current limit

decreases at higher input-to-output differential voltages. See the Typical

Performance Characteristics graphs for more information.

Note 10.

This IC includes over-temperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperature will exceed the maximum operating junction temperature

when over-temperature protection is active. Continuous operation above

the specified maximum operating junction temperature may impair

device reliability.

For more information

www.analog.com

Rev. C

LT3085

TYPICAL PERFORMANCE CHARACTERISTICS

Set Pin Current

10.20

10.15

SET PIN CURRENT (µA)

10.10

10.05

10.00

9.95

9.90

9.85

9.80

–50 –25

25 50 75 100 125 150

TEMPERATURE (°C)

3085 G01

Set Pin Current Distribution

2.0

N = 1676

Offset Voltage (V

OUT

– V

SET

)

1.5

OFFSET VOLTAGE (mV)

1.0

0.5

–0.5

–1.0

–1.5

9.80

10.00

10.20

9.90

10.10

SET PIN CURRENT DISTRIBUTION (µA)

3085 G02

–2.0

–50 –25

25 50 75 100 125 150

TEMPERATURE (°C)

3085 G03

Offset Voltage Distribution

1.00

N = 1676

Offset Voltage

0.75

OFFSET VOLTAGE (mV)

0.50

0.25

–0.25

–0.50

–0.75

LOAD

= 1mA

Offset Voltage

0.25

OFFSET VOLTAGE (mV)

–0.25

–0.50

–0.75

–1.00

–1.25

–1.50

= 25°C

= 125°C

–2

–1

DISTRIBUTION (mV)

3085 G04

–1.00

INPUT-TO-OUTPUT VOLTAGE (V)

3085 G05

–1.75

0 50 100 150 200 250 300 350 400 450 500

LOAD CURRENT (mA)

3085 G06

CHANGE IN OFFSET VOLTAGE WITH LOAD (mV)

–0.1

–0.2

–0.3

–0.4

–0.5

–0.6

–0.7

Load Regulation

∆I

LOAD

= 1mA TO 500mA

– V

OUT

= 2V

CHANGE IN REFERENCE CURRENT

Minimum Load Current

–10

–20

Dropout Voltage

(Minimum IN Voltage)

400

MINIMUM IN VOLTAGE (V

– V

OUT

) (mV)

350

300

250

200

150

100

50 100 150 200 250 300 350 400 450 500

LOAD CURRENT (mA)

3085 G09

0.8

MINIMUM LOAD CURRENT (mA)

0.7

0.6

0.5

0.4

0.3

0.2

0.1

–50 –25

IN, CONTROL

– V

OUT

= 1.5V

IN, CONTROL

– V

OUT

= 36V

CHANGE IN REFERENCE CURRENT

WITH LOAD (nA)

= 125°C

OUT

– V

SET

)

–30

–40

= 25°C

CHANGE IN OFFSET VOLTAGE

–50

–0.8

–50 –25

–60

25 50 75 100 125 150

TEMPERATURE (°C)

3085 G07

100 125 150

3085 G08

TEMPERATURE (°C)

Rev. C

For more information

www.analog.com

LT3085

TYPICAL PERFORMANCE CHARACTERISTICS

Dropout Voltage

(Minimum IN Voltage)

400

MINIMUM IN VOLTAGE (V

– V

OUT

) (mV)

350

300

250

200

150

100

–50 –25

25 50 75 100 125 150

TEMPERATURE (°C)

3085 G10

Dropout Voltage (Minimum

CONTROL

Pin Voltage)

1.6

1.4

MINIMUM CONTROL VOLTAGE

CONTROL

– V

OUT

) (V)

1.6

Dropout Voltage (Minimum

CONTROL

Pin Voltage)

1.4

MINIMUM CONTROL VOLTAGE

CONTROL

– V

OUT

) (V)

1.2

1.0

0.8

0.6

0.4

0.2

LOAD

= 100mA

LOAD

= 500mA

LOAD

= 500mA

= –50°C

1.2

1.0

0.8

0.6

0.4

0.2

0 50 100 150 200 250 300 350 400 450 500

LOAD CURRENT (mA)

3085 G11

= 125°C

= 25°C

LOAD

= 100mA

–50 –25

25 50 75 100 125 150

TEMPERATURE (°C)

3085 G12

Current Limit

700

600

CURRENT LIMIT (mA)

Current Limit

700

600

CURRENT LIMIT (mA)

500

400

300

200

100

10 15 20 25 30 35

INPUT-TO-OUTPUT DIFFERENTIAL (V)

LOAD CURRENT

(mA)

OUTPUT VOLTAGE

DEVIATION (mV)

Load Transient Response

= 25°C

–20

–40

200

100

20 40 60 80 100 120 140 160 180 200

TIME (µs)

3085 G15

OUT

= 1.5V

SET

= 0.1µF

= V

CONTROL

= 3V

500

400

300

200

100

= 7V

OUT

= 0V

OUT

= 10µF CERAMIC

OUT

= 2.2µF CERAMIC

–50 –25

25 50 75 100 125 150

TEMPERATURE (°C)

3085 G13

3085 G14

Load Transient Response

150

OUTPUT VOLTAGE

DEVIATION (mV)

100

–50

OUT

= 2.2µF CERAMIC

= V

CONTROL

= 3V

OUT

= 1.5V

SET

= 0.1µF

0 10

20 30 40 50 60 70 80 90 100

TIME (µs)

3085 G16

Line Transient Response

OUTPUT VOLTAGE (V)

Turn-On Response

1.5

0.5

IN/CONTROL

VOLTAGE (V)

8 10 12 14 16 18 20

TIME (µs)

3085 G18

100

OUT

= 10µF CERAMIC

OUTPUT VOLTAGE

DEVIATION (mV)

–50

OUT

= 1.5V

LOAD

= 10mA

OUT

= 2.2µF

CERAMIC

SET

= 0.1µF

CERAMIC

–100

OUT

= 2.2µF

CERAMIC

SET

= 100k

SET

= 0

LOAD

= 2

LOAD CURRENT

(mA)

–100

500

250

IN/CONTROL

VOLTAGE (V)

10 20 30 40 50 60 70 80 90 100

TIME (µs)

3085 G17

For more information

www.analog.com

Rev. C