LT1129/LT1129-3.3/LT1129-5
O U
W
U
PPLICATI
A
S I FOR ATIO
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.
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 of the LT1129 is forced to a voltage below
its nominal output voltage and its output is held high, the
outputcurrentwillfollowthecurveshowninFigure6.This
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
≤ 0.8V
≤ 0.8V
Open
SHDN PIN
Open (Hi)
Grounded
Open (Hi)
Grounded
Open (Hi)
Grounded
OUTPUT/SENSE PINS
Forced to V
(Nominal)
(Nominal)
Reverse Output Current ≈ 15µA (See Figure 3)
Reverse Output Current ≈ 15µA (See Figure 3)
Reverse Output Current ≈ 200µA Peak (See Figure 4)
OUT
OUT
Forced to V
> 1V
> 1V
Open
Reverse Output Current ≈ 35µA at V
= V
(Nominal) (See Figure 5)
OUT
OUT
0.8V ≤ V ≤ V
Forced to V
(Nominal)
(Nominal)
Reverse Output Current ≈ 300µA Peak (See Figure 6)
Reverse Output Current ≈ 300µA (See Figure 6)
IN
OUT
OUT
OUT
OUT
0.8V ≤ V ≤ V
Forced to V
IN
100
90
40
T
= 25°C
J
V
V
V
= OPEN
IN
V
= 0V
IN
SENSE
35
30
25
20
15
10
5
= 0V
SHDN
SENSE
V
= V
OUT
80
= V
OUT
CURRENT FLOWS
70 INTO DEVICE
LT1129-5
LT1129-3.3
60
50
40
30
20
10
0
LT1129
LT1129-3.3
LT1129-5
0
0
2
4
6
8
10
1
2
5
1
3
5
7
9
0
3
4
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1129 F03
1129 F05
Figure 3. Reverse Output Current
Figure 5. Reverse Output Current
350
300
250
200
150
100
50
350
300
250
200
150
100
50
V
= V
OUT
SENSE
V
V
V
= OPEN
IN
= OPEN
SHDN
SENSE
= V
OUT
LT1129-5
LT1129-3.3
LT1129-5
= 5V
LT1129-3.3
= 3.3V
V
V
OUT
OUT
0
0
1
2
3
5
1
2
5
0
4
0
3
4
OUTPUT VOLTAGE (V)
INPUT VOLTAGE (V)
1129 F04
1129 F06
Figure 6. Reverse Output Current
Figure 4. Reverse Output Current
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-
tationthattheinterconnectionofitscircuitsasdescribedhereinwillnotinfringeonexistingpatentrights.
11
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