LP2985AIM5X-2.0 Datasheet, PDF (12/22 Pages) Texas Instruments – LP2985LV-N Micropower 150 mA Low-Noise Low-Dropout Regulator in SOT-23 and DSBGA packages for Applications with Output Voltages 2.0V

LP2985LV-N
SNOS510P – NOVEMBER 1999 – REVISED APRIL 2013
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REVERSE INPUT-OUTPUT VOLTAGE
The PNP power transistor used as the pass element in the LP2985LV-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.
V_IN
V_OUT
PNP
GND
Figure 37. Normal Operation
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_IN (and out the
ground pin), which 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_IN to V_OUT (cathode on V_IN, anode on V_OUT), to limit the reverse voltage across the LP2985LV-N
to 0.3V (see ABSOLUTE MAXIMUM RATINGS).
SCHOTTKY DIODE
V_IN
V_OUT
PNP
GND
Figure 38. Operation with Schottky Diode
DSBGA MOUNTING
The DSBGA package requires specific mounting techniques which are detailed in Texas Instruments Application
Note AN-1112. Referring to the section Surface Mount Technology (SMT) Assembly Considerations, it should be
noted that the pad style which must be used with the 5-pin package is the NSMD (non-solder mask defined)
type.
For best results during assembly, alignment ordinals on the PC board may be used to facilitate placement of the
DSBGA device.
DSBGA LIGHT SENSITIVITY
Exposing the DSBGA device to direct sunlight will cause misoperation of the device. Light sources such as
Halogen lamps can also affect electrical performance if brought near to the device.
The wavelengths which have the most detrimental effect are reds and infra-reds, which means that the
fluorescent lighting used inside most buildings has very little effect on performance. A DSBGA test board was
brought to within 1 cm of a fluorescent desk lamp and the effect on the regulated output voltage was negligible,
showing a deviation of less than 0.1% from nominal.
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