11

LT1129/LT1129-3.3/LT1129-5

S

APPLICATI

I FOR ATIO

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

OUTPUT VOLTAGE (V)

0

100

90

80

70

60

50

40

30

20

10

0

8

1129 F03

2

4

6

10

13

57

9

CURRENT FLOWS

INTO DEVICE

LT1129-3.3

LT1129

LT1129-5

Figure 5. Reverse Output Current

Figure 3. Reverse Output Current

INPUT VOLTAGE (V)

0

350

300

250

200

150

100

50

0

3

1129 F06

12

5

4

LT1129-3.3

LT1129-5

Figure 6. Reverse Output Current

OUTPUT VOLTAGE (V)

0

40

35

30

25

20

15

10

5

0

3

1129 F05

12

5

4

LT1129-3.3

LT1129-5

OUTPUT VOLTAGE (V)

0

350

300

250

200

150

100

50

0

3

1129 F04

12

5

4

LT1129-3.3

LT1129-5

Figure 4. Reverse Output Current

shutdown pin floating (open circuit). Figure 5 shows

output current as a function of output voltage with the

input floating and the shutdown pin pulled to ground.

When the input of the LT1129 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 6 . This

can happen if the input of the LT1129 is connected to a

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

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

Users with applications requiring lower reverse currents

should contact the factory about the availability of a

modified version of the LT1129.

Table 4. Fault Conditions

INPUT PIN

SHDN PIN

OUTPUT/SENSE PINS

≤ 0.8V

Open (Hi)

Reverse Output Current

≈ 15µA (See Figure 3)

≤ 0.8V

Grounded

Reverse Output Current

≈ 15µA (See Figure 3)

Open

Open (Hi)

> 1V

Reverse Output Current

≈ 200µA Peak (See Figure 4)

Open

Grounded

> 1V

Reverse Output Current

0.8V

Open (Hi)

Reverse Output Current

≈ 300µA Peak (See Figure 6)

0.8V

Grounded

Reverse Output Current

≈ 300µA (See Figure 6)