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LT1185

Low Dropout Regulator

Linear Technology 

LT1185

ELECTRICAL CHARACTERISTICS

The ● denotes specifications which apply over the operating temperature range, otherwise specifications are at TA = 25°C.

Adjustable version, VIN = 7.4V, VOUT = 5V, IOUT = 1mA, RLIM = 4.02k, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

Load Regulation (Note 7)

Line Regulation (Note 7)

Minimum Input Voltage

Internal Current Limit (See Graph for

Guaranteed Curve) (Note 12)

IOUT = 5mA to 3A

VIN – VOUT = 1.5V to 10V, VOUT = 5V

0.05

0.3

VIN – VOUT = 1V to 20V, VOUT = 5V

0.002

0.01

IOUT = 1A (Note 4), VOUT = VREF

4.0

IOUT = 3A

4.3

1.5V ≤ VIN – VOUT ≤ 10V

VIN – VOUT = 15V

VIN – VOUT = 20V

VIN – VOUT = 30V

3.3

3.6

4.2

●

3.1

4.4

●

2.0

3.0

4.2

●

1.0

1.7

2.6

●

0.2

0.4

1.0

UNITS

%

%/ V

V

V

A

A

A

A

A

External Current Limit

Programming Constant

External Current Limit Error

Quiescent Supply Current

Supply Current Change with Load

REF Pin Shutoff Current

Thermal Regulation (See Applications

Information)

Reference Voltage Temperature Coefficient

Thermal Resistance Junction to Case

5k ≤ RLIM ≤ 15k, VOUT = 1V

(Note 11)

1A ≤ ILIM ≤ 3A

RLIM = 15k • A/ILIM

IOUT = 5mA, VOUT = VREF

4V ≤ VIN ≤ 25V (Note 5)

VIN – VOUT = VSAT (Note 10)

VIN – VOUT ≥ 2V

VIN – VOUT = 10V

IOUT = 5mA to 2A

(Note 8)

TO-3 Control Area

Power Transistor

TO-220 Control Area

Power Transistor

●

15k

A•Ω

0.02 ILIM 0.06 ILIM + 0.03

A

●

0.04 ILIM 0.09 ILIM + 0.05

A

●

2.5

3.5

mA

●

●

●

0.4

25

10

2

0.005

40

25

7

0.014

mA/A

mA/A

µA

%/ W

0.003

0.01

1

3

1

3

%/°C

°C/W

°C/W

°C/W

°C/W

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: Reference voltage is guaranteed both at nominal conditions (no

load, 25°C) and at worst-case conditions of load, line, power and

temperature. An intermediate value can be calculated by adding the effects

of these variables in the actual application. See the Applications

Information section of this data sheet.

Note 3: Dropout voltage is tested by reducing input voltage until the

output drops 1% below its nominal value. Tests are done at 0.5A and 3A.

The power transistor looks basically like a pure resistance in this range so

that minimum differential at any intermediate current can be calculated by

interpolation; VDROPOUT = 0.25V + 0.25Ω • IOUT. For load current less than

0.5A, see graph.

Note 4: “Minimum input voltage” is limited by base emitter voltage drive

of the power transistor section, not saturation as measured in Note 3. For

output voltages below 4V, “minimum input voltage” specification may limit

dropout voltage before transistor saturation limitation.

Note 5: Supply current is measured on the ground pin, and does not

include load current, RLIM, or output divider current.

Note 6: The 25W power level is guaranteed for an input-output voltage of

8.3V to 17V. At lower voltages the 3A limit applies, and at higher voltages

the internal power limiting may restrict regulator power below 25W. See

graphs.

Note 7: Line and load regulation are measured on a pulse basis with a

pulse width of ≈ 2ms, to minimize heating. DC regulation will be affected

by thermal regulation and temperature coefficient of the reference. See

Applications Information section for details.

Note 8: Guaranteed by design and correlation to other tests, but not

tested.

Note 9: TJMIN = 0°C for the LT1185C, – 40°C for LT1185I, and –55°C for

the LT1185M. Power transistor area and control circuit area have different

maximum junction temperatures. Control area limits are TJMAX = 125°C for

the LT1185C and LT1185I and 150°C for the LT1185M. Power area limits

are 150°C for LT1185C and LT1185I and 175°C for LT1185M.

Note 10: VSAT is the maximum specified dropout voltage;

0.25V + 0.25 • IOUT.

Note 11: Current limit is programmed with a resistor from REF pin to GND

pin. The value is 15k/ILIM.

Note 12: For VIN – VOUT = 1.5V; VIN = 5V, VOUT = 3.5V. VOUT = 1V for all

other current limit tests.

1185ff

3

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