LP3987

SNVS164G – OCTOBER 2001 – REVISED MAY 2013

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ON/OFF INPUT OPERATION

MODE OPERATION

The LP3987 enters sleep mode by pulling MODE = 0V externally to reduce current during standby operation.

During sleep mode, LP3987 consumes only 14µA of quiescent current and supplies up to 3mA of current. The

device returns to active mode by pulling MODE = 1.8V. If this function is not used, the MODE pin should be tied

THERMAL PROTECTION

The LP3987 has internal thermal protection circuitry to disable the internal pass transistor if the junction

temperature exceeds 125°C to allow the device to cool down. The pass transistor will turn on when temperature

falls below the maximum operating junction temperature of 125°C. This feature is designed to protect the device

in the event of fault conditions. For normal operation, it is suggested to limit the device junction temperature to

less than 125°C.

DSBGA MOUNTING

The DSBGA package requires specific mounting techniques which are detailed in Texas Instruments AN-1112

Application Report (SNOA401). Referring to the section PCB Layout, note that the pad style which must be used

with the 5 pin package is 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 effect electrical performance if brought near to the device. The wavelengths which have 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 1cm 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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