LT1763 datasheet(19/22 Pages) LINER

19 / 22 page

LT1763 Series

1763fg

Figure 7. Reverse Output Current

The top resistor of the resistor divider must be chosen to

limit the current into the ADJ pin to less than 5mA when

the ADJ pin is at 7V. The 13V difference between output

and ADJ pin divided by the 5mA maximum current into the

ADJ pin yields a minimum top resistor value of 2.6k.

In circuits where a backup battery is required, several

different input/output conditions can occur. The output

voltage may be held up while the input is either pulled

to ground, pulled to some intermediate voltage or is left

open-circuit. Current ﬂow back into the output will follow

the curve shown in Figure 7.

When the IN pin of the LT1763-X is forced below the OUT

pin, or the OUT pin is pulled above the IN pin, input cur-

rent will typically drop to less than 2μA. This can happen

if the input of the device is connected to a discharged

(low voltage) battery and the output is held up by either

a backup battery or a second regulator circuit. The state

of the SHDN pin will have no effect on the reverse output

current when the output is pulled above the input.

OUTPUT VOLTAGE (V)

100

1763 F07

0123

TJ = 25°C

VIN = 0V

CURRENT FLOWS

INTO OUTPUT PIN

VOUT = VADJ (LT1763)

LT1763

LT1763-5

LT1763-3.3

LT1763-1.5

LT1763-1.8

LT1763-2.5

LT1763-3

APPLICATIONS INFORMATION

LT1763 Datasheet(PDF) 19 Page - Linear Technology