To assure proper operation, the signal source used to drive

the Shutdown input must be able to swing above and below

the specified turn-on/turn-off voltage thresholds listed in the

Electrical Characteristics section under V

REVERSE INPUT-OUTPUT VOLTAGE

The PNP power transistor used as the pass element in the

LP3878 has an inherent diode connected between the regu-

lator output and input.

During normal operation (where the input voltage is higher

than the output) this diode is reverse-biased.

However, if the output is pulled above the input, this diode

will turn ON and current will flow into the regulator output.

In such cases, a parasitic SCR can latch which will allow a

high current to flow into V

can damage the part.

In any application where the output may be pulled above the

input, an external Schottky diode must be connected from

V

reverse voltage across the LP3878 to 0.3V (see Absolute

Maximum Ratings).

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