tantalum will increase about 2:1 as the temperature goes

from 25˚C down to -40˚C, so some guard band must be

allowed.

ENABLE CONTROL

The LP3990 features an active high Enable pin, V

turns the device on when pulled high. When not enabled the

regulator output is off and the device typically consumes

2nA.

If the application does not require the Enable switching

feature, the V

regulator output permanently on.

To ensure proper operation, the signal source used to drive

the V

specified turn-on/off voltage thresholds listed in the Electrical

Characteristics section under V

Micro SMD MOUNTING

The micro SMD package requires specific mounting tech-

niques, which are detailed in National Semiconductor Appli-

cation Note AN-1112.

For best results during assembly, alignment ordinals on the

PC board may be used to facilitate placement of the micro

SMD device.

Micro SMD LIGHT SENSITIVITY

Exposing the micro SMD device to direct light may affect the

operation of the device. Light sources, such as halogen

lamps, can affect electrical performance, if placed in close

proximity to the device.

Light with wavelengths in the infra-red portion of the spec-

trum is the most detrimental, and so, fluorescent lighting

used inside most buildings, has little or no effect on perfor-

mance.

www.national.com

11