ANALOG DEVICES LT 3080EMS8E, LT 3080 EST Datasheet

LT3080

Adjustable1.1A Single

Resistor Low Dropout

Regulator

FeaTures

n

Outputs May be Paralleled for Higher Current and

Heat Spreading

n

Output Current: 1.1A

n

Single Resistor Programs Output Voltage

n

1% Initial Accuracy of SET Pin Current

n

Output Adjustable to 0V

n

Low Output Noise: 40µV

n

Wide Input Voltage Range: 1.2V to 36V

n

Low Dropout Voltage: 350mV (Except SOT-223

(10Hz to 100kHz)

RMS

Package)

n

<1mV Load Regulation

n

<0.001%/V Line Regulation

n

Minimum Load Current: 0.5mA

n

Stable with 2.2µF Minimum Ceramic Output Capacitor

n

Current Limit with Foldback and Overtemperature

Protected

n

Available in 8-Lead MSOP, 3mm × 3mm DFN,

5-Lead DD-Pak, TO-220 and 3-Lead SOT-223

applicaTions

n

High Current All Surface Mount Supply

n

High Efficiency Linear Regulator

n

Post Regulator for Switching Supplies

n

Low Parts Count Variable Voltage Supply

n

Low Output Voltage Power Supplies

DescripTion

The LT®3080 is a 1.1A low dropout linear regulator that can
be paralleled to increase output current or spread heat in
surface mounted boards. Architected as a precision cur­rent source and voltage follower allows this new regulator
to be used in many applications requiring high current,
adjustability to zero, and no heat sink. Also the device
brings out the collector of the pass transistor to allow low
dropout operation —down to 350 millivolts— when used
with multiple supplies.

A key feature of the LT3080 is the capability to supply a
wide output voltage range. By using a reference current
through a single resistor, the output voltage is programmed
to any level between zero and 36V. The LT3080 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 LT3080 regulator is offered in the
8-lead MSOP (with an exposed pad for better thermal
characteristics), a 3mm × 3mm DFN, 5-lead DD-Pak,
TO-220 and a simple-to-use 3-lead SOT-223 version.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and VLDO
and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners.

Typical applicaTion

Variable Output Voltage 1.1A Supply

SET

LT3080

R

SET

V

OUT

+
–

= R

SET

V

1.2V TO 36V
V

CONTROL

1µF

IN

IN

• 10µA

OUT

3080 TA01a

V

OUT

2.2µF

Set Pin Current Distribution

N = 13792

9.80

9.90

SET PIN CURRENT DISTRIBUTION (µA)

10.00

10.10

10.20

3080 G02

3080fc

1

LT3080

absoluTe MaxiMuM raTings

V

CONTROL

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

(Note 1)(All Voltages Relative to V

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

SET Pin Current (Note 7) .....................................±10mA

SET Pin Voltage (Relative to OUT) .........................±0.3V

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

pin conFiguraTion

TOP VIEW

1OUT

OUT

2

OUT

3

SET

4

8-LEAD (3mm × 3mm) PLASTIC DFN

T

= 125°C, θJA = 64°C/W, θJC = 3°C/W

JMAX

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

9

OUT

DD PACKAGE

8
7

6
5

IN
IN
NC
V

CONTROL

OUT

1

OUT

2

OUT

3

SET

4

MS8E PACKAGE

8-LEAD PLASTIC MSOP

= 125°C, θJA = 60°C/W, θJC = 10°C/W

T

JMAX

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

)

OUT

Operating Junction Temperature Range (Notes 2, 10)

E-, I-Grades ............................................ –40°C to 125°C

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

Lead Temperature (Soldering, 10 sec)

MS8E, Q, T and ST Packages Only .................... 300°C

TOP VIEW

9

OUT

8
7
6
5

IN
IN
NC
V

CONTROL

TAB IS

OUT

T

FRONT VIEW

5
4
3
2
1

Q PACKAGE

5-LEAD PLASTIC DD-PAK

= 125°C, θJA = 30°C/W, θJC = 3°C/W

JMAX

IN
V

CONTROL

OUT
SET
NC

TAB IS

OUT

FRONT VIEW

5
4
3
2
1

T PACKAGE

5-LEAD PLASTIC TO-220

T

= 125°C, θJA = 40°C/W, θJC = 3°C/W

JMAX

IN
V

CONTROL

OUT
SET
NC

FRONT VIEW

TAB IS

OUT

ST PACKAGE

3-LEAD PLASTIC SOT-223

*IN IS V

T

JMAX

AND IN TIED TOGETHER

CONTROL

= 125°C, θJA = 55°C/W, θJC = 15°C/W

3

IN*

2

OUT

1

SET

2

3080fc

LT3080

orDer inForMaTion

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LT3080EDD#PBF LT3080EDD#TRPBF LCBN 8-Lead (3mm x 3mm) Plastic DFN –40°C to 125°C
LT3080IDD#PBF LT3080IDD#TRPBF LCBN 8-Lead (3mm x 3mm) Plastic DFN –40°C to 125°C
LT3080EMS8E#PBF LT3080EMS8E#TRPBF LTCBM 8-Lead Plastic MSOP –40°C to 125°C
LT3080IMS8E#PBF LT3080IMS8E#TRPBF LTCBM 8-Lead Plastic MSOP –40°C to 125°C
LT3080EQ#PBF LT3080EQ#TRPBF LT3080Q 5-Lead Plastic DD-Pak –40°C to 125°C
LT3080IQ#PBF LT3080IQ#TRPBF LT3080Q 5-Lead Plastic DD-Pak –40°C to 125°C
LT3080ET#PBF LT3080ET#TRPBF LT3080ET 5-Lead Plastic TO-220 –40°C to 125°C
LT3080IT#PBF LT3080IT#TRPBF LT3080ET 5-Lead Plastic TO-220 –40°C to 125°C
LT3080EST#PBF LT3080EST#TRPBF 3080 3-Lead Plastic SOT-223 –40°C to 125°C

LT3080IST#PBF LT3080IST#TRPBF 3080 3-Lead Plastic SOT-223 –40°C to 125°C

LEAD BASED FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LT3080EDD LT3080EDD#TR LCBN 8-Lead (3mm x 3mm) Plastic DFN –40°C to 125°C
LT3080IDD LT3080IDD#TR LCBN 8-Lead (3mm x 3mm) Plastic DFN –40°C to 125°C
LT3080EMS8E LT3080EMS8E#TR LTCBM 8-Lead Plastic MSOP –40°C to 125°C
LT3080IMS8E LT3080IMS8E#TR LTCBM 8-Lead Plastic MSOP –40°C to 125°C
LT3080EQ LT3080EQ#TR LT3080Q 5-Lead Plastic DD-Pak –40°C to 125°C
LT3080IQ LT3080IQ#TR LT3080Q 5-Lead Plastic DD-Pak –40°C to 125°C
LT3080ET LT3080ET#TR LT3080ET 5-Lead Plastic TO-220 –40°C to 125°C
LT3080IT LT3080IT#TR LT3080ET 5-Lead Plastic TO-220 –40°C to 125°C
LT3080EST LT3080EST#TR 3080 3-Lead Plastic SOT-223 –40°C to 125°C
LT3080IST LT3080IST#TR 3080 3-Lead Plastic SOT-223 –40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/

For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/

3080fc

3

LT3080

The l denotes the specifications which apply over the full operating

elecTrical characTerisTics

temperature range, otherwise specifications are at TA = 25°C. (Note 11)

PARAMETER CONDITIONS MIN TYP MAX UNITS

SET Pin Current I

Output Offset Voltage (V
VIN = 1V, V

CONTROL

= 2V, I

OUT

OUT

– V

SET)

= 1mA

SETVIN

V

= 1V, V

V

≥ 1V, V

IN

DFN and MSOP Package

OS

CONTROL
CONTROL

= 2.0V, I

= 1mA, TJ = 25°C

LOAD

≥ 2.0V, 1mA ≤ I

≤ 1.1A (Note 9)

LOAD

SOT-223, DD-Pak and T0-220 Package

Load Regulation

Line Regulation (Note 9)
DFN and MSOP Package

Line Regulation (Note 9)
SOT-223, DD-Pak and T0-220 Package

Minimum Load Current (Notes 3, 9) V

V

V

V

Dropout Voltage (Note 4) I

CONTROL

Dropout Voltage (Note 4) I

IN

Pin Current I

CONTROL

Current Limit V
Error Amplifier RMS Output Noise (Note 6) I

ΔI
ΔV

ΔI
ΔV

ΔI

ΔV

SET

OS

SET

OS

SET

OS

ΔI
ΔI

VIN = 1V to 25V, V
V

VIN = 1V to 26V, V
V

V
V

I

I

I

1mA to 1.1A

LOAD =

1mA to 1.1A (Note 8)

LOAD =

= 1V to 25V, V

IN

= 1V to 26V, V

IN

= V

IN

CONTROL

= V

IN

CONTROL

= V

IN

CONTROL

= 100mA

LOAD

= 1.1A

LOAD

= 100mA

LOAD

= 1.1A

LOAD

= 100mA

LOAD

= 1.1A

LOAD

= 5V, V

IN

= 1.1A, 10Hz ≤ f ≤ 100kHz, C

LOAD

CONTROL
CONTROL

CONTROL
CONTROL

= 10V

= 25V (DFN and MSOP Package)

= 26V (SOT-223, DD-Pak and T0-220 Package)

= 5V, V

CONTROL

= 2V to 25V, I
= 2V to 25V, I

= 2V to 26V, I
= 2V to 26V, I

= 0V, V

SET

OUT

= 1mA

LOAD

= 1mA

LOAD

= 1mA

LOAD

= 1mA

LOAD

= –0.1V

OUT

= 10µF, C

= 0.1µF 40 µV

SET

Reference Current RMS Output Noise (Note 6) 10Hz ≤ f ≤ 100kHz 1 nA
Ripple Rejection f = 120Hz, V

RIPPLE

= 0.5V

P-P

, I

LOAD

= 0.2A, C

= 0.1µF, C

SET

OUT

= 2.2µF
f = 10kHz
f = 1MHz

Thermal Regulation, I

SET

10ms Pulse 0.003 %/W

9.90

l

9.80

l

–3.5

10 1010.10

10.20

–2

3.5

–5

l

–6

l

l

–0.1

0.6 1.3

0.1

0.5 nA/V

0.003

l

0.1

0.5 nA/V

0.003

l
l
l

l

l
l

l
l

l

300 500

1.2

1.35 1.6
100

200

350

500

4

176 30

1.1 1.4 A

75
55
20

µA
µA

2

mV
mV

5
6

mV
mV

nA

mV

mV/V

mV/V

µA
1
1

mA
mA

mV
mV

mA
mA

RMS

RMS

dB

dB

dB

V
V

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 LT3080 is tested and specified under pulse load conditions such that
T

≅ TA. The LT3080E is tested at TA = 25°C. Performance of the LT3080E

J

over the full –40°C and 125°C operating temperature range is assured by
design, characterization, and correlation with statistical process controls.
The LT3080I is guaranteed over the full –40°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 LT3080, dropout is caused by either minimum control
voltage (V

) or minimum input voltage (VIN). Both parameters are

CONTROL

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

pin current is the drive current required for the

CONTROL

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.

4

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: SET pin is clamped to the output with diodes. These diodes only
carry current under transient overloads.

Note 8: Load regulation is Kelvin sensed at the package.
Note 9: Current limit may decrease to zero at input-to-output differential

voltages (V

) greater than 25V (DFN and MSOP package) or 26V

IN–VOUT

(SOT-223, DD-Pak and T0-220 Package). Operation at voltages for both IN
and V

is allowed up to a maximum of 36V as long as the difference

CONTROL

between input and output voltage is below the specified differential
(V

) voltage. Line and load regulation specifications are not

IN–VOUT

applicable when the device is in current limit.
Note 10: This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction
temperature will exceed the maximum operating junction temperature when
overtemperature protection is active. Continuous operation above the specified
maximum operating junction temperature may impair device reliability.

Note 11: The SOT-223 package connects the IN and V

CONTROL

pins
together internally. Therefore, test conditions for this pin follow the
V

conditions listed in the Electrical Characteristics Table.

CONTROL

3080fc

Typical perForMance characTerisTics

LT3080

Set Pin Current Set Pin Current Distribution Offset Voltage (V

10.20

10.15

10.10

10.05

10.00

9.95

SET PIN CURRENT (µA)

9.90

9.85

9.80
–25

–50

0

25

TEMPERATURE (°C)

Offset Voltage Distribution

N = 13250

–2

–1

VOS DISTRIBUTION (mV)

N = 13792

50

75

100

125

150

3080 G01

9.80

9.90

SET PIN CURRENT DISTRIBUTION (µA)

10.00

10.10

10.20

3080 G02

Offset Voltage Offset Voltage

1.00
I

= 1mA

LOAD

0.75

0.50

0.25

0

–0.25

OFFSET VOLTAGE (mV)

–0.50

–0.75

0

1

3080 G04

–1.00

2

6 12 24

0

INPUT-TO-OUTPUT VOLTAGE (V)

*SEE NOTE 9 IN ELECTRICAL

CHARACTERISTICS TABLE

18

30

36*

3080 G05

2.0

1.5

1.0

0.5

0

–0.5

OFFSET VOLTAGE (mV)

–1.0

–1.5

–2.0

–50

0.25

0

–0.25

–0.50

–0.75

–1.00

OFFSET VOLTAGE (mV)

–1.25

–1.50

–1.75

IL = 1mA

–25

0

Dropout Voltage

Load Regulation Minimum Load Current

0

∆I

= 1mA TO 1.1A

LOAD

– V

V

–0.1

–0.2

–0.3

–0.4

–0.5

–0.6

–0.7

CHANGE IN OFFSET VOLTAGE WITH LOAD (mV)

–0.8

–50

= 2V

IN

OUT

CHANGE IN REFERENCE CURRENT

CHANGE IN OFFSET VOLTAGE

(V

– V

)

SET

50

75

–25

0

OUT

25

TEMPERATURE (°C)

100

125

3080 G07

CHANGE IN REFERENCE CURRENT WITH LOAD (nA)

150

20

10

0

–10

–20

–30

–40

–50

–60

0.8

0.7

V

0.6

0.5

0.4

0.3

0.2

MINIMUM LOAD CURRENT (mA)

0.1

0

IN, CONTROL

V

IN, CONTROL

–25

–50

*SEE NOTE 9 IN ELECTRICAL

0

TEMPERATURE (°C)

CHARACTERISTICS TABLE

– V

= 36V*

OUT

– V

= 1.5V

OUT

50

75

25

100

125

150

3080 G08

(Minimum IN Voltage)

400

350

) (mV)

OUT

300

– V

250

IN

200

150

100

50

MINIMUM IN VOLTAGE (V

0

0

– V

OUT

50

0

25

TEMPERATURE (°C)

TJ = 125°C

0.2 0.4 0.8
LOAD CURRENT (A)

0.2 0.4 0.8

OUTPUT CURRENT (A)

75

TJ = 25°C

0.6

TJ = 125°C

0.6

)

SET

100

125

1.0

TJ = 25°C

1.0

150

3080 G03

1.2

3080 G06

1.2

3080 G09

3080fc

5

LT3080

5

Typical perForMance characTerisTics

Dropout Voltage
(Minimum IN Voltage)

400

350

) (mV)

OUT

300

– V

IN

250

200

150

100

50

MINIMUM IN VOLTAGE (V

0

–25

–50

0

TEMPERATURE (°C)

Current Limit

1.6

1.4

1.2

1.0

0.8

0.6

CURRENT LIMIT (A)

0.4

VIN = 7V

0.2
= 0V

V

OUT

0

–25

–50

0

TEMPERATURE (°C)

Dropout Voltage (Minimum
V

CONTROL

) (V)

1.6

OUT

1.4

I

= 1.1A

LOAD

I

= 500mA

LOAD

I

= 100mA

LOAD

50

75

25

100

125

150

3080 G10

– V

1.2

CONTROL

1.0

0.8

0.6

0.4

0.2

0

0

MINIMUM CONTROL VOLTAGE (V

Pin Voltage)

TJ = –50°C

TJ = 125°C

TJ = 25°C

0.2 0.4 0.8

0.6

OUTPUT CURRENT (A)

1.0

1.2

3080 G11

Current Limit

1.6

1.4

1.2

1.0

0.8

0.6

CURRENT LIMIT (A)

50

75

25

100

125

150

3080 G13

MSOP

0.4

0.2

0

6 12 24

0

INPUT-TO-OUTPUT DIFFERENTIAL (V)

*SEE NOTE 9 IN ELECTRICAL

CHARACTERISTICS TABLE

SOT-223, DD-PAK
AND TO-220

AND

DFN

18

TJ = 25°C

30

3080 G14

36*

Dropout Voltage (Minimum

) (V)

1.6

OUT

1.4

– V

1.2

CONTROL

1.0

0.8

0.6

0.4

0.2

0

MINIMUM CONTROL VOLTAGE (V

–50

V

CONTROL

–25

0

Pin Voltage)

I

LOAD

25

TEMPERATURE (°C)

Load Transient Response

75

50

25

0

–25

DEVIATION (mV)LOAD CURRENT (mA)

OUTPUT VOLTAGE

–50

400

300

200

100

0

0

C

OUT

C

= 2.2µF CERAMIC

OUT

105

I

LOAD

= 1mA

50

75

V

= 1.5V

OUT

= 0.1µF

C

SET

= V

V

IN

= 10µF CERAMIC

30 35 45

2015

25

TIME (µs)

= 1.1A

100

CONTROL

40

125

150

3080 G12

= 3V

50

3080 G15

Load Transient Response Line Transient Response

150

100

50

0

–50

DEVIATION (mV)LOAD CURRENT (A)

OUTPUT VOLTAGE

–100

1.2

0.9

0.6

0.3

VIN = V
V

OUT

C

OUT

= 0.1µF

C

SET

0

105

0

2015

25

TIME (µs)

30 35 45

= 3V

CONTROL

= 1.5V
= 10µF CERAMIC

40

3080 G16

50

75

50

25

0

–25

DEVIATION (mV)

OUTPUT VOLTAGE

–50

6

5

4

3

2

IN/CONTROL VOLTAGE (V)

2010

0

4030

50

TIME (µs)

V

= 1.5V

OUT

= 10mA

I

LOAD

= 2.2µF

C

OUT

CERAMIC

= 0.1µF

C

SET

CERAMIC

60 70 90

80

100

3080 G17

Turn-On Response

4

3

2

1

0

2.0

1.5

1.0

0.5

0

OUTPUT VOLTAGE (V) INPUT VOLTAGE (V)

21

0

R

SET

C

SET

R

LOAD

C

OUT

43

5

TIME (µs)

= 100k

= 0

= 1Ω

= 2.2µF CERAMIC

6 7 9

8

10

3080 G18

3080fc

6

Typical perForMance characTerisTics

CONTROL PIN CURRENT (mA)

25

CONTROL PIN CURRENT (mA)

30

OUTPUT VOLTAGE (V)

0.8

RIPPLE REJECTION (dB)

100

RIPPLE REJECTION (dB)

100

RIPPLE REJECTION (dB)

ERROR AMPLIFIER NOISE

REFERENCE CURRENT NOISE

10k

1k

V

CONTROL

20

15

10

5

0

0

*SEE NOTE 9 IN ELECTRICAL

CHARACTERISTICS TABLE

Pin Current

I

= 1.1A

LOAD

DEVICE IN
CURRENT LIMIT

= 1mA

I

LOAD

12 18 24

6

INPUT-TO-OUTPUT DIFFERENTIAL (V)

Ripple Rejection, Single Supply

90

80

70

60

50

40

30

20

VIN = V
RIPPLE = 50mV

10

C

OUT

0

I

= 1.1A

LOAD

= V

CONTROL

P-P

= 2.2µF CERAMIC

FREQUENCY (Hz)

I

LOAD

OUT (NOMINAL)

10k 100k10010 1k 1M

= 100mA

+ 2V

30 36*

3080 G19

3080 G22

V

CONTROL

V
V

25

20

15

10

5

0

0

Ripple Rejection, Dual Supply,
V

CONTROL

90

80

70

60

50

40

30

VIN = V

20

V
C

10

RIPPLE = 50mV

0

Pin Current

– V

CONTROL

– V

= 1V

IN

OUT

0.2
LOAD CURRENT (A)

Pin

I

LOAD

OUT (NOMINAL)

= V

CONTROL

= 2.2µF CERAMIC

OUT

= 2V

OUT

= –50°C

T

J

= 125°C

T

J

0.4 0.6 0.8

I

= 1.1A

+ 1V

OUT (NOMINAL)

P-P

FREQUENCY (Hz)

+2V

10k 100k10010 1k 1M

T

LOAD

= 25°C

J

1.0 1.2

= 100mA

3080 G23

3080 G20

LT3080

Residual Output Voltage with
Less Than Minimum Load

SET PIN = 0V

0.7

V

IN

0.6

0.5

0.4

0.3

0.2

0.1

0

VIN = 20V

0

Ripple Rejection, Dual Supply,
IN Pin

100

90

80

70

60

50

40

VIN = V

30

20

10

0

OUT (NOMINAL)

V

CONTROL

RIPPLE = 50mV
C

= 2.2µF CERAMIC

OUT

= 1.1A

I

LOAD

V

R

TEST

VIN = 10V

R

TEST

= V

OUT (NOMINAL)

P-P

FREQUENCY (Hz)

OUT

V

= 5V

IN

(Ω)

+ 1V

+2V

10k 100k10010 1k 1M

2k1k

3080 G21

3080 G24

Ripple Rejection (120Hz)

80

79

78

77

76

75

74

73

RIPPLE REJECTION (dB)

72

71

70

–50

SINGLE SUPPLY OPERATION

= V

V

IN

RIPPLE = 500mV
I

LOAD

= 0.1µF, C

C

SET

–25 25

OUT(NOMINAL)

= 1.1A

P-P

= 2.2µF

OUT

0

TEMPERATURE (°C)

+ 2V

, f = 120Hz

50

75

100

125

3080 G25

150

Noise Spectral Density

1k

100

10

SPECTRAL DENSITY (nV/√Hz)

1

FREQUENCY (Hz)

SPECTRAL DENSITY (pA/ √Hz)

100

10

1.0

10k 100k10010 1k

0.1

3080 G26

3080fc

7

LT3080

GAIN (dB)

PHASE (DEGREES)

20

300

Typical perForMance characTerisTics

Output Voltage Noise

V

OUT

100µV/DIV

V

OUT

R

SET

= O.1µF

C

SET

C

OUT

I

LOAD

pin FuncTions

V

CONTROL

(Pin 5/Pin 5/Pin 4/Pin 4/NA): This pin is the

= 1V
= 100k

= 10µF

= 1.1A

TIME 1ms/DIV

(DD/MS8E/Q/T/ST)

3080 G27

supply pin for the control circuitry of the device. The cur­rent flow into this pin is about 1.7% of the output current.
For the device to regulate, this voltage must be more than

1.2V to 1.35V greater than the output voltage (see dropout
specifications).

IN (Pins 7, 8/Pins 7, 8/Pin 5/Pin 5/Pin 3): This is the
collector to the power device of the LT3080. The output
load current is supplied through this pin. For the device
to regulate, the voltage at this pin must be more than

0.1V to 0.5V greater than the output voltage (see dropout
specifications).

NC (Pin 6/Pin 6/Pin 1/Pin 1/NA): No Connection. No con­nect pins have no connection to internal circuitry and may
be tied to V

IN

, V

CONTROL

, V

, GND or floated.

OUT

Error Amplifier Gain and Phase

–10

–15

–20

–25

–30

15

10

5

0

–5

FREQUENCY (Hz)

IL = 1.1A

I

= 100mA

L

IL = 1.1A

IL = 100mA

10k 100k10010 1k 1M

250

200

150

100

50

0

–50

–100

–150

–200

3080 G28

OUT (Pins 1-3/Pins 1-3/Pin 3/Pin 3/Pin 2): This is the
power output of the device. There must be a minimum
load current of 1mA or the output may not regulate.

SET (Pin 4/Pin 4/Pin 2/Pin 2/Pin 1): This pin is the input
to the error amplifier and the regulation set point for
the device. A fixed current of 10µA flows out of this pin
through a single external resistor, which programs the
output voltage of the device. Output voltage range is zero
to the absolute maximum rated output voltage. Transient
performance can be improved by adding a small capacitor
from the SET pin to ground.

Exposed Pad (Pin 9/Pin 9/NA/NA/NA): OUT on MS8E and
DFN packages.

TAB: OUT on DD-Pak, TO-220 and SOT-223 packages.

3080fc

8

block DiagraM

IN

V

CONTROL

applicaTions inForMaTion

LT3080

10µA

+

–

3080 BD

OUTSET

The LT3080 regulator is easy to use and has all the pro­tection features expected in high performance regulators.
Included are short-circuit protection and safe operating
area protection, as well as thermal shutdown.

The LT3080 is especially well suited to applications needing
multiple rails. The new architecture adjusts down to zero
with a single resistor handling modern low voltage digital
IC’s as well as allowing easy parallel operation and thermal
management without heat sinks. Adjusting to “zero” output
allows shutting off the powered circuitry and when the
input is pre-regulated—such as a 5V or 3.3V input supply
—external resistors can help spread the heat.

A precision “0” TC 10µA internal current source is con­nected to the noninverting input of a power operational
amplifier. The power operational amplifier provides a low
impedance buffered output to the voltage on the noninvert­ing input. A single resistor from the noninverting input to
ground sets the output voltage and if this resistor is set
to zero, zero output results. As can be seen, any output
voltage can be obtained from zero up to the maximum
defined by the input power supply.

What is not so obvious from this architecture are the ben­efits of using a true internal current source as the reference
as opposed to a bootstrapped reference in older regulators.
A true current source allows the regulator to have gain
and frequency response independent of the impedance on
the positive input. Older adjustable regulators, such as the

LT1086 have a change in loop gain with output voltage
as well as bandwidth changes when the adjustment pin
is bypassed to ground. For the LT3080, the loop gain is
unchanged by changing the output voltage or bypassing.
Output regulation is not fixed at a percentage of the output
voltage but is a fixed fraction of millivolts. Use of a true
current source allows all the gain in the buffer amplifier
to provide regulation and none of that gain is needed to
amplify up the reference to a higher output voltage.

The LT3080 has the collector of the output transistor
connected to a separate pin from the control input. Since
the dropout on the collector (IN pin) is only 350mV, two
supplies can be used to power the LT3080 to reduce dis­sipation: a higher voltage supply for the control circuitry
and a lower voltage supply for the collector. This increases
efficiency and reduces dissipation. To further spread the
heat, a resistor can be inserted in series with the collector
to move some of the heat out of the IC and spread it on
the PC board.

The LT3080 can be operated in two modes. Three-terminal
mode has the control pin connected to the power input pin
which gives a limitation of 1.35V dropout. Alternatively,
the “control” pin can be tied to a higher voltage and the
power IN pin to a lower voltage giving 350mV dropout
on the IN pin and minimizing the power dissipation. This
allows for a 1.1A supply regulating from 2.5V
or 1.8V

to 1.2V

IN

with low dissipation.

OUT

IN

to 1.8V

OUT

3080fc

9