LP2953AI-3.3 datasheet(16/22 Pages) NSC

16 / 22 page

Application Hints (Continued)

SHUTDOWN INPUT

A logic-level signal will shut off the regulator output when a

“LOW” (<1.2V) is applied to the Shutdown input.

To prevent possible mis-operation, the Shutdown input must

be actively terminated. If the input is driven from open-

collector logic, a pull-up resistor (20 k

Ω to 100 kΩ recom-

mended) should be connected from the Shutdown input to

the regulator input.

If the Shutdown input is driven from a source that actively

pulls high and low (like an op-amp), the pull-up resistor is not

required, but may be used.

If the shutdown function is not to be used, the cost of the

pull-up resistor can be saved by simply tying the Shutdown

input directly to the regulator input.

IMPORTANT: Since the Absolute Maximum Ratings state

that the Shutdown input can not go more than 0.3V below

ground, the reverse-battery protection feature which protects

the regulator input is sacrificed if the Shutdown input is tied

directly to the regulator input.

If reverse-battery protection is required in an application, the

pull-up resistor between the Shutdown input and the regula-

tor input must be used.

Typical Applications

Basic 5V Regulator

01112715

5V Current Limiter with Load Fault Indicator

01112716

* Output voltage equals +VIN minum dropout voltage, which varies with

output current. Current limits at a maximum of 380 mA (typical).

** Select R1 so that the comparator input voltage is 1.23V at the output

voltage which corresponds to the desired fault current value.

Low T.C. Current Sink

01112717

LP2953AI-3.3 Datasheet(PDF) 16 Page - National Semiconductor (TI)