LP2985AIM5-135/NOPB National Semiconductor, LP2985AIM5-135/NOPB Datasheet - Page 12

• Manufacturer Part Number: LP2985AIM5-135/NOPB
• Description: IC REG LDO 150MA 1.35V SOT23-5
• Manufacturer: National Semiconductor

Specifications of LP2985AIM5-135/NOPB

• Regulator Topology: Positive Fixed
• Voltage - Output: 1.35V
• Voltage - Input: 2.5 ~ 16 V
• Voltage - Dropout (typical): 0.28V @ 150mA
• Number Of Regulators: 1
• Current - Output: 150mA
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Limit (min): -
• Other names: LP2985AIM5-135; LP2985AIM5-135TR

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One disadvantage of ceramic capacitors is that their capaci-
tance can vary with temperature. Most large value ceramic
capacitors (
temperature characteristic, which results in the capacitance
dropping by more than 50% as the temperature goes from 25°
C to 85°C.
This could cause problems if a 2.2 µF capacitor were used on
the output since it will drop down to approximately 1 µF at high
ambient temperatures (which could cause the LP2985LV to
oscillate). If Z5U or Y5V capacitors are used on the output, a
minimum capacitance value of 4.7 µF must be observed.
A better choice for temperature coefficient in ceramic capac-
itors is X7R, which holds the capacitance within ±15%. Un-
fortunately, the larger values of capacitance are not offered
by all manufacturers in the X7R dielectric.
Tantalum
Tantalum capacitors are less desirable than ceramics for use
as output capacitors because they are more expensive when
comparing equivalent capacitance and voltage ratings in the
1 µF to 4.7 µF range.
Another important consideration is that Tantalum capacitors
have higher ESR values than equivalent size ceramics. This
means that while it may be possible to find a Tantalum ca-
pacitor with an ESR value within the stable range, it would
have to be larger in capacitance (which means bigger and
more costly) than a ceramic capacitor with the same ESR
value.
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 LP2985LV 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 Elec-
trical Characteristics section under V
operation, the turn-on (and turn-off) voltage signals applied to
the ON/OFF input must have a slew rate which is
≥
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 list-
ed under the electrical specification V
Characteristics).
REVERSE INPUT-OUTPUT VOLTAGE
The PNP power transistor used as the pass element in the
LP2985LV has an inherent diode connected between the reg-
ulator output and input. During normal operation (where the
input voltage is higher than the output) this diode is reverse-
biased.
40 mV/µs.
≥
2.2 µF) are manufactured with the Z5U or Y5V
ON/OFF
IN
ON/OFF
to keep the regulator
. To prevent mis-
(see Electrical
12
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 cur-
rent 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
verse voltage across the LP2985LV 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 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 perfor-
mance. A micro SMD 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.
IN
to V
OUT
FIGURE 4. Reverse Current Protection
(cathode on V
FIGURE 3. Reverse Current Parth
IN
(and out the ground pin), which can
IN
, anode on V
OUT
), to limit the re-
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