PNP

GND

SCHOTTKY DIODE

PNP

GND

LP2985-N

www.ti.com

SNVS018V – MARCH 2000 – REVISED JUNE 2013

REVERSE INPUT-OUTPUT VOLTAGE

The PNP power transistor used as the pass element in the LP2985-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).

Figure 37. Reverse Current Path

However, if the output is pulled above the input, this diode will turn ON and current will flow into the regulator

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

0.3V (see ABSOLUTE MAXIMUM RATINGS).

Figure 38. Reverse Current Protection

DSBGA MOUNTING

The DSBGA package requires specific mounting techniques which are detailed in Texas Instruments Application

Note 1112 (SNVA009). 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 wavelenghts 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.

Copyright © 2000–2013, Texas Instruments Incorporated

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Product Folder Links: LP2985-N