Datasheet

V
IN
V
OUT
PNP
GND
SCHOTTKY DIODE
V
IN
V
OUT
PNP
GND
LP2980-N
SNOS733M –APRIL 2000–REVISED JUNE 2013 www.ti.com
Figure 37. LP2980 Reverse Current Path
However, if the input voltage is more than a V
BE
below the output voltage, 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
the V
IN
pin and out the ground pin, which can damage the part.
The internal diode can also be turned on if the input voltage is abruptly stepped down to a voltage which is a V
BE
below the output voltage.
In any application where the output voltage may be higher than the input voltage, an external Schottky diode
must be connected from V
IN
to V
OUT
(cathode on V
IN
, anode on V
OUT
. See Figure 38), to limit the reverse voltage
across the LP2980-N to 0.3V (See ABSOLUTE MAXIMUM RATINGS).
Figure 38. Adding External Schottky Diode Protection
ON/OFF INPUT OPERATION
The LP2980-N is shut off by pulling the ON/OFF input low, and turned on by driving the input high. If this feature
is not to be used, the ON/OFF input should be tied to V
IN
to keep the regulator on at all times (the ON/OFF input
must not be left floating).
To ensure proper operation, the signal source used to drive the ON/OFF input must be able to swing above and
below the specified turn-on/turn-off voltage thresholds which ensure an ON or OFF state (see ELECTRICAL
CHARACTERISTICS).
The ON/OFF signal may come from either a totem-pole output, or an open-collector output with pull-up resistor to
the LP2980-N input voltage or another logic supply. The high-level voltage may exceed the LP2980-N input
voltage, but must remain within the Absolute Maximum Ratings for the ON/OFF pin.
It is also important that the turn-on/turn-off voltage signals applied to the ON/OFF input have a slew rate which is
greater than 40 mV/μs.
IMPORTANT: The regulator shutdown function will not operate correctly if a slow-moving signal is used to drive
the ON/OFF input.
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