LP2986 Datasheet, PDF (18/33 Pages) National Semiconductor (TI) – Micropower, 200 mA Ultra Low-Dropout Fixed or Adjustable Voltage Regulator

LP2986
SNVS137I – MARCH 1999 – REVISED SEPTEMBER 2015
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A typical aluminum electrolytic can exhibit an ESR increase of 50× when going from +20°C to −40°C. Also, some
aluminum electrolytics can not be used below −25°C because the electrolyte will freeze.
8.2.2.4 Reverse Input-Output Voltage
The PNP power transistor used as the pass element in the LP2986 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.
However, if the output voltage is pulled above the input, or the input voltage is pulled below the output, this diode
will turn ON and current will flow into the regulator OUT pin.
LP2986
V_IN
PNP
V_OUT
GND
Figure 33. Inherent Diode
In such cases, a parasitic SCR can latch which will allow a high current to flow into V_IN (and out the GROUND
pin), which can damage the part.
In any application where the output voltage may be higher than the input, an external Schottky diode must be
connected from V_IN to V_OUT (cathode on V_IN, anode on V_OUT), to limit the reverse voltage across the LP2986 to
0.3 V (see Absolute Maximum Ratings).
SCHOTTKY DIODE
LP2986
V_IN
PNP
V_OUT
GND
Figure 34. Inherent and External Schottky Diodes
8.2.2.5 WSON Package Devices
The LP2986 is offered in the 8-pin WSON surface mount package to allow for increased power dissipation
compared to the 8-pin SOIC-8 and 8-pin VSSOP. For details on WSON thermal performance as well as
mounting and soldering specifications, refer to WSON Mounting.
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