Datasheet

11
LT1129/LT1129-3.3/LT1129-5
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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
OUTPUT PIN CURRENT (µA)
100
90
80
70
60
50
40
30
20
10
0
8
1129 F03
2
4
6
10
13579
T
J
= 25°C
V
IN
= 0V
V
SENSE
= V
OUT

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
OUTPUT CURRENT (µA)
4
LT1129-3.3
V
OUT
= 3.3V

V
SENSE
= V
OUT
LT1129-5
V
OUT
= 5V
Figure 6. Reverse Output Current
OUTPUT VOLTAGE (V)
0
40
35
30
25
20
15
10
5
0
3
1129 F05
12 5
OUTPUT CURRENT (µA)
4
LT1129-3.3
LT1129-5
V
IN
= OPEN
V
SHDN
= 0V
V
SENSE
= V
OUT
OUTPUT VOLTAGE (V)
0
350
300
250
200
150
100
50
0
3
1129 F04
12 5
OUTPUT CURRENT (µA)
4
V
IN
= OPEN
V
SHDN
= OPEN
V
SENSE
= V
OUT
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) Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15µA (See Figure 3)
≤ 0.8V Grounded Forced to V
OUT
(Nominal) 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 ≈ 35µA at V
OUT
= V
OUT
(Nominal) (See Figure 5)
0.8V ≤ V
IN
≤ V
OUT
Open (Hi) Forced to V
OUT
(Nominal) Reverse Output Current ≈ 300µA Peak (See Figure 6)
0.8V ≤ V
IN
≤ V
OUT
Grounded Forced to V
OUT
(Nominal) Reverse Output Current ≈ 300µA (See Figure 6)