Datasheet

12
LT1129/LT1129-3.3/LT1129-5
112935fd
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 3. Reverse Output Current
INPUT VOLTAGE (V)
0
INPUT CURRENT (μA)
5
4
3
2
1
0
4
1129 F04
1
2
3
5
V
OUT
= 3.3V (LT1129-3.3)
V
OUT
= 5V (LT1129-5)
Figure 4. Input Current
In some applications it may be necessary to leave the input
to the LT1129 unconnected when the output is held high.
This can happen when the LT1129 is powered from a
rectified AC source. If the AC source is removed, then the
input of the LT1129 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 shutdown pin will have no
effect on the reverse output current when the input pin is
floating.
When the input of the LT1129 is forced to a voltage below
its nominal output voltage and its output is held high, the
reverse output current will still follow the curve shown in
Figure 3. 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.
When the input pin is forced below the output 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 shutdown pin will have no effect on the reverse
output current when the output is pulled above the input.
APPLICATIO S I FOR ATIO
WUU
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Table 4. Fault Conditions
INPUT PIN SHDN PIN OUTPUT PIN
< V
OUT
(Nominal) Open (Hi) Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15μA (See Figure 3)
Input Current ≈ 1μA (See Figure 4)
< V
OUT
(Nominal) Grounded Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15μA (See Figure 3)
Input Current ≈ 1μA (See Figure 4)
Open Open (Hi) Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15μA (See Figure 3)
Open Grounded Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15μA (See Figure 3)