Datasheet

11
LT1121/LT1121-3.3/LT1121-5
U
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AT
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I FOR ATIO
When the input of the LT1121 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 in Figure
2. This condition can occur if the input of the LT1121 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 3). The state of the shutdown pin will have no effect
on the reverse output current when the output is pulled
above the input.
INPUT VOLTAGE (V)
0
INPUT CURRENT (µA)
5
4
3
2
1
0
4
1121 F03
1
2
3
5
V
OUT
= 3.3V (LT1121-3.3)
V
OUT
= 5V (LT1121-5)
Figure 3. Input Current
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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.
Table 6. Fault Conditions
INPUT PIN SHDN PIN OUTPUT PIN
< V
OUT
(Nominal) Open (Hi) Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15µA (See Figure 2)
Input Current ≈ 1µA (See Figure 3)
< V
OUT
(Nominal) Grounded Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15µA (See Figure 2)
Input Current ≈ 1µA (See Figure 3)
Open Open (Hi) Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15µA (See Figure 2)
Open Grounded Forced to V
OUT
(Nominal) Reverse Output Current ≈ 15µA (See Figure 2)
≤ 0.8V Open (Hi) ≤ 0V Output Current = 0
≤ 0.8V Grounded ≤ 0V Output Current = 0
> 1.5V Open (Hi) ≤ 0V Output Current = Short-Circuit Current
–30V < V
IN
< 30V Grounded ≤ 0V Output Current = 0