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LT1521

300mA Low Dropout Regulators with Micropower Quiescent Current and Shutdown

Linear Technology 

LT1521/LT1521-3

LT1521-3.3/LT1521-5

ELECTRICAL CHARACTERISTICS

PARAMETER

CONDITIONS

MIN

TYP

MAX UNITS

Input Reverse Leakage Current

Reverse Output Current (Note 11)

VIN = – 20V, VOUT = 0V

q

LT1521-3

LT1521-3.3

LT1521-5

LT1521 (Note 5)

VOUT = 3V, VIN < 3V, TJ = 25°C

VOUT = 3.3V, VIN < 3.3V, TJ = 25°C

VOUT = 5V, VIN < 5V, TJ = 25°C

VOUT = 3.8V, VIN < 3.75V, TJ = 25°C

1.0

mA

5

10

µA

5

10

µA

5

10

µA

5

10

µA

The q denotes specifications which apply over the full operating

temperature range.

Note 5: The LT1521 (adjustable version) is tested and specified with the

adjust pin connected to the output pin.

Note 1: Absolute Maximum Ratings are those values beyond which the life

of a device may be impaired.

Note 2: The shutdown pin input voltage rating is required for a low

impedance source. Internal protection devices connected to the shutdown

pin will turn on and clamp the pin to approximately 7V or – 0.6V. This

range allows the use of 5V logic devices to drive the pin directly. For high

impedance sources or logic running on supply voltages greater than 5.5V,

the maximum current driven into the shutdown pin must be limited to less

than 5mA.

Note 3: For junction temperatures greater than 110°C, a minimum load of

1mA is recommended. For TJ > 110°C and IOUT < 1mA, output voltage

may increase by 1%.

Note 4: Operating conditions are limited by maximum junction

temperature. The regulated output voltage specification will not apply for

all possible combinations of input voltage and output current. When

operating at maximum input voltage, the output current range must be

limited. When operating at maximum output current, the input voltage

range must be limited.

Note 6: Dropout voltage is the minimum input/output voltage required to

maintain regulation at the specified output current. In dropout the output

voltage will be equal to: (VIN – VDROPOUT)

Note 7: Ground pin current is tested with VIN = VOUT (nominal) and a

current source load. This means the device is tested while operating in its

dropout region. This is the worst-case ground pin current. The ground pin

current will decrease slightly at higher input voltages.

Note 8: Adjust pin bias current flows into the adjust pin.

Note 9: Shutdown pin current at VSHDN = 0V flows out of the shutdown

pin.

Note 10: Quiescent current in shutdown is equal to the total sum of the

shutdown pin current (2µA) and the ground pin current (4µA).

Note 11: Reverse output current is tested with the input pin grounded and

the output pin forced to the rated output voltage. This current flows into

the output pin and out of the ground pin.

TYPICAL PERFORMANCE CHARACTERISTICS

Guaranteed Dropout Voltage

0.8

= TEST POINTS

0.7

0.6

TJ ≤ 125°C

0.5

0.4

TJ ≤ 25°C

0.3

0.2

0.1

0

0 50 100 150 200 250 300

OUTPUT CURRENT (mA)

LT1521 • TPC01

Dropout Voltage

0.8

0.7

0.6

ILOAD = 300mA

0.5

ILOAD = 150mA

0.4

ILOAD = 100mA

0.3

0.2

ILOAD = 50mA

0.1

ILOAD = 1mA

0

–50 –25

0 25 50 75

TEMPERATURE (°C)

100 125

LT1521 • TPC02

Quiescent Current

15.0

12.5

VSHDN = OPEN

10.0

7.5

5.0

VSHDN = 0V

VIN = 6V

2.5 RL = ∞

ILOAD = 0

0

–50 –25

0 25 50 75

TEMPERATURE (°C)

100 125

LT1521 • TPC03

4

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