LP2985AIM5-3.3 National Semiconductor, LP2985AIM5-3.3 Datasheet - Page 16

• Manufacturer Part Number: LP2985AIM5-3.3
• Description: V REG LDO +3.3V, SMD, 2985, SOT235
• Manufacturer: National Semiconductor

Specifications of LP2985AIM5-3.3

• Primary Input Voltage: 4.3V
• Output Voltage: 3.3V
• Dropout Voltage Vdo: 280mV
• No. Of Pins: 5
• Output Current: 150mA
• Voltage Regulator Case Style: SOT-23
• Operating Temperature Range: -40°C To +125°C
• Output Voltage Fixed: 3.3V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

www.national.com
Application Hints
It should also be noted that the ESR of a typical Tantalum will
increase about 2:1 as the temperature goes from 25˚C down
to −40˚C, so some guard band must be allowed.
On/off Input Operation
The LP2985 is shut off by driving the ON/OFF input low, and
turned on by pulling it high. If this feature is not to be used,
the ON/OFF input should be tied to V
output on at all times.
To assure proper operation, the signal source used to drive
the ON/OFF input must be able to swing above and below
the specified turn-on/turn-off voltage thresholds listed in the
Electrical Characteristics section under V
mis-operation, the turn-on (and turn-off) voltage signals ap-
plied to the ON/OFF input must have a slew rate which is
≥ 40 mV/µs.
Caution: the regulator output voltage can not be guaranteed
if a slow-moving AC (or DC) signal is applied that is in the
range between the specified turn-on and turn-off voltages
listed under the electrical specification V
cal Characteristics).
REVERSE INPUT-OUTPUT VOLTAGE
The PNP power transistor used as the pass element in the
LP2985 has an inherent diode connected between the regu-
lator output and input. During normal operation (where the
input voltage is higher than the output) this diode is reverse-
biased.
However, if the output is pulled above the input, this diode
will turn ON and current will flow into the regulator output. In
(Continued)
IN
to keep the regulator
ON/OFF
ON/OFF
(see Electri-
. To prevent
16
such cases, a parasitic SCR can latch which will allow a high
current to flow into V
damage the part.
In any application where the output may be pulled above the
input, an external Schottky diode must be connected from
V
reverse voltage across the LP2985 to 0.3V (see Absolute
Maximum Ratings).
MICRO SMD MOUNTING
The micro SMD package requires specific mounting tech-
niques which are detailed in National Semiconductor Appli-
cation Note # 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 micro
SMD device.
MICRO SMD LIGHT SENSITIVITY
Exposing the micro SMD 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 light-
ing used inside most buildings has very little effect on per-
formance. A micro SMD test board was brought to within 1
cm of a fluorescent desk lamp and the effect on the regu-
lated output voltage was negligible, showing a deviation of
less than 0.1% from nominal.
IN
to V
OUT
(cathode on V
IN
(and out the ground pin), which can
IN
, anode on V
OUT
), to limit the