LP2985IM5-2.0 National Semiconductor, LP2985IM5-2.0 Datasheet - Page 11

• Manufacturer Part Number: LP2985IM5-2.0
• Description: IC REG LDO 150MA 2.0V LN SOT23-5
• Manufacturer: National Semiconductor

Specifications of LP2985IM5-2.0

• Regulator Topology: Positive Fixed
• Voltage - Output: 2V
• Voltage - Input: Up to 16V
• 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: Contains lead / RoHS non-compliant
• Current - Limit (min): -
• Other names: LP2985IM5-2.0TR

Application Hints
EXTERNAL CAPACITORS
Like any low-dropout regulator, the LP2985LV requires ex-
ternal capacitors for regulator stability. These capacitors must
be correctly selected for good performance.
Input Capacitor
An input capacitor whose capacitance is
between the LP2985LV input and ground (the amount of ca-
pacitance may be increased without limit).
This capacitor must be located a distance of not more than 1
cm from the input pin and returned to a clean analog ground.
Any good quality ceramic, tantalum, or film capacitor may be
used at the input.
Important: Tantalum capacitors can suffer catastrophic fail-
ure due to surge current when connected to a low-impedance
source of power (like a battery or very large capacitor). If a
Tantalum capacitor is used at the input, it must be guaranteed
by the manufacturer to have a surge current rating sufficient
for the application.
There are no requirements for ESR on the input capacitor, but
tolerance and temperature coefficient must be considered
when selecting the capacitor to ensure the capacitance will
be
Output Capacitor
The LP2985LV is designed specifically to work with ceramic
output capacitors, utilizing circuitry which allows the regulator
to be stable across the entire range of output current with an
output capacitor whose ESR is as low as 5 mΩ. It may also
be possible to use Tantalum or film capacitors at the output,
but these are not as attractive for reasons of size and cost
(see next sectionCapacitor Characteristics).
The output capacitor must meet the requirement for minimum
amount of capacitance and also have an ESR (equivalent se-
ries resistance) value which is within the stable range. Curves
are provided which show the stable ESR range as a function
of load current (see ESR graphs
≥
1 µF over the entire operating temperature range.
FIGURE 1. LP2985LV 2.2µF Stable ESR Range
Figure 1
≥
and
1 µF is required
Figure
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2).
11
Important: The output capacitor must maintain its ESR within
the stable region over the full operating temperature range of
the application to assure stability.
The LP2985LV requires a minimum of 2.2 µF on the output
(output capacitor size can be increased without limit).
It is important to remember that capacitor tolerance and vari-
ation with temperature must be taken into consideration when
selecting an output capacitor so that the minimum required
amount of output capacitance is provided over the full oper-
ating temperature range. It should be noted that ceramic
capacitors can exhibit large changes in capacitance with tem-
perature (see next section, Capacitor Characteristics).
The output capacitor must be located not more than 1 cm from
the output pin and returned to a clean analog ground.
Noise Bypass Capacitor
Connecting a 10 nF capacitor to the Bypass pin significantly
reduces noise on the regulator output. It should be noted that
the capacitor is connected directly to a high-impedance circuit
in the bandgap reference.
Because this circuit has only a few microamperes flowing in
it, any significant loading on this node will cause a change in
the regulated output voltage. For this reason, DC leakage
current through the noise bypass capacitor must never ex-
ceed 100 nA, and should be kept as low as possible for best
output voltage accuracy.
The types of capacitors best suited for the noise bypass ca-
pacitor are ceramic and film. High-quality ceramic capacitors
with either NPO or COG dielectric typically have very low
leakage. 10 nF polypropolene and polycarbonate film capac-
itors are available in small surface-mount packages and typ-
ically have extremely low leakage current.
CAPACITOR CHARACTERISTICS
The LP2985LV was designed to work with ceramic capacitors
on the output to take advantage of the benefits they offer: for
capacitance values in the 2.2 µF to 4.7 µF range, ceramics
are the least expensive and also have the lowest ESR values
(which makes them best for eliminating high-frequency
noise). The ESR of a typical 2.2 µF ceramic capacitor is in the
range of 10 mΩ to 20 mΩ, which easily meets the ESR limits
required for stability by the LP2985LV.
FIGURE 2. LP2985LV 4.7µF Stable ESR Range
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