LT1528 データシートの表示（PDF） - Linear Technology

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LT1528

3A Low Dropout Regulator for Microprocessor Applications

Linear Technology 

LT1528

APPLICATIONS INFORMATION

The reverse output current will follow the curve in Figure

3 when the input is pulled to ground. This current flows

through the OUTPUT pin to ground. The state of the

SHDN pin will have no effect on output current when the

input pin is pulled to ground.

In some applications it may be necessary to leave the

input on the LT1528 unconnected when the output is held

high. This can happen when the LT1528 is powered from

a rectified AC source. If the AC source is removed, then

the input of the LT1528 is effectively left floating. The

reverse output current also follows the curve in Figure

3 if the input pin is left open. The state of the SHDN pin

will have no effect on the reverse output current when

the input pin is floating.

When the input of the LT1528 is forced to a voltage below

its nominal output voltage and its output is held high, the

output current will follow the curve shown in Figure 3.

This can happen if the input of the LT1528 is connected

to a low voltage and the output is held up by a second

regulator circuit. When the input pin is forced below the

0utput pin or the OUTPUT pin is pulled above the input

pin, the input current will typically drop to less than 2μA

(see Figure 4). The state of the SHDN pin will have no

effect on the reverse output current when the output is

pulled above the input.

1000

900

800

700

TJ = 25°C, VIN = 0V

VOUT = VSENSE

CURRENT FLOWS

INTO DEVICE

600

500

400

300

200

100

0

01

23 45 678

OUTPUT VOLTAGE (V)

9 10

1528 F03

Figure 3. Reverse Output Current

5

VOUT = 3.3V

4

3

2

1

0

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

INPUT VOLTAGE (V)

1528 F04

Figure 4. Input Current

1528fb

10

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