LT1528
10
1528fb
The reverse output current will follow the curve in Figure
3 when the input is pulled to ground. This current fl ows
through the OUTPUT pin to ground. The state of the
SHDN pin will have no effect on output current when the
input pin is pulled to ground.
In some applications it may be necessary to leave the
input on the LT1528 unconnected when the output is held
high. This can happen when the LT1528 is powered from
a rectifi ed AC source. If the AC source is removed, then
the input of the LT1528 is effectively left fl oating. The
reverse output current also follows the curve in Figure
3 if the input pin is left open. The state of the SHDN pin
will have no effect on the reverse output current when
the input pin is fl oating.
When the input of the LT1528 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 3.
This can happen if the input of the LT1528 is connected
to a low voltage and the output is held up by a second
regulator circuit. When the input pin is forced below the
0utput 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 SHDN pin will have no
effect on the reverse output current when the output is
pulled above the input.
Figure 3. Reverse Output Current
OUTPUT VOLTAGE (V)
0
OUTPUT CURRENT (μA)
1000
900
800
700
600
500
400
300
200
100
0
8
1528 F03
213579
4
6
10
T
J
= 25°C, V
IN
= 0V
V
OUT
= V
SENSE
CURRENT FLOWS
INTO DEVICE
Figure 4. Input Current
INPUT VOLTAGE (V)
0
0
INPUT CURRENT (μA)
2
5
1.0
2.0
2.5
1528 F04
1
4
3
0.5
1.5
3.0
3.5
V
OUT
= 3.3V
APPLICATIONS INFORMATION
