Datasheet

V
IN
V
OUT
PNP
GND
SCHOTTKY DIODE
LP2981-N
V
IN
V
OUT
PNP
GND
LP2981-N
LP2981-N
www.ti.com SNOS773K –MARCH 2000–REVISED APRIL 2013
Figure 37. 3V/10 μF ESR Curves
REVERSE CURRENT PATH
The internal PNP power transistor used as the pass element in the LP2981-N has an inherent diode connected
between the regulator output and input. During normal operation (where the input voltage is higher than the
output) this diode is reverse biased (See Figure 38).
Figure 38. LP2981-N 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 39), to limit the reverse voltage
across the LP2981-N to 0.3V (see Absolute Maximum Ratings)
Figure 39. Adding External Schottky Diode Protection
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