LP2952 Datasheet, PDF (17/24 Pages) National Semiconductor (TI) – Adjustable Micropower Low-Dropout Voltage Regulators

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 kΩ 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
5V Current Limiter with Load Fault Indicator
01112716
* Output voltage equals +V_IN 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
01112715
01112717
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