13

LT3023

3023f

In circuits where a backup battery is required, several

different input/output conditions can occur. The output

voltage may be held up while the input is either pulled to

ground, pulled to some intermediate voltage or is left open

circuit. Current flow back into the output will follow the

curve shown in Figure 6.

When the IN pin of the LT3023 is forced below the OUT1

or OUT2 pins or the OUT1/OUT2 pins are pulled above the

IN pin, input current will typically drop to less than 2

µA.

This can happen if the input of the device is connected to

a discharged (low voltage) battery and the output is held

up by either a backup battery or a second regulator circuit.

The state of the SHDN1/SHDN2 pins will have no effect on

the reverse output current when the output is pulled above

the input.

Figure 6. Reverse Output Current

APPLICATIO S I FOR ATIO

OUTPUT VOLTAGE (V)

100

90

80

760

60

50

40

30

20

10

0

3023 F06

0123

4

5

67

8

9

10

CURRENT FLOWS

INTO OUTPUT PIN

TYPICAL APPLICATIO S

OUT1

BYP1

ADJ1

OUT2

BYP2

ADJ2

IN

SHDN1

SHDN2

LT3023

1

µF

3.7V TO 20V

OFF ON

0.01

µF

0.01

µF

422k

261k

249k

249k

10

µF

10

µF

3023 TA02a

3.3V

AT 100mA

2.5V

AT 100mA

GND

1V/DIV

1V/DIV

1V/DIV

2ms/DIV

3023 TA02b

10

0.1

1

10

100

100

1000

10000

3023 TA02c

Noise Bypassing Slows Startup, Allows Outputs to Track

Startup Time