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PDF LP2985LV Data sheet ( Hoja de datos )
| Número de pieza | LP2985LV | |
| Descripción | Micropower 150mA Low-Noise Low-Dropout Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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LP2985LV
September 9, 2010
Micropower 150 mA Low-Noise Low-Dropout Regulator in
SOT-23 and micro SMD packages for Applications with
Output Voltages ≤ 2.0V
Designed for Use with Very Low ESR Output Capacitors
General Description
The LP2985LV is a 150 mA, fixed-output voltage regulator
designed to providehigh performance and low noise in appli-
cations requiring output voltages ≤ 2.0V.
Using an optimized VIP® (Vertically Integrated PNP) process,
the LP2985LV delivers unequalled performance in all speci-
fications critical to battery-powered designs:
Ground Pin Current: Typically 825 µA @ 150 mA load, and
75 µA @ 1 mA load.
Enhanced Stability: The LP2985LV is stable with output ca-
pacitor ESR as low as 5 mΩ, which allows the use of ceramic
capacitors on the output.
Sleep Mode: Less than 1 µA quiescent current when ON/OFF
pin is pulled low.
Smallest Possible Size: micro SMD package uses absolute
minimum board space.
Precision Output: 1% tolerance output voltages available (A
grade).
Low Noise: By adding a 10 nF bypass capacitor, output noise
can be reduced to 30 µV (typical).
Features
■ Guaranteed 150 mA output current
■ Smallest possible size (micro SMD)
■ Requires minimum external components
■ Stable with low-ESR output capacitor
■ <1 µA quiescent current when shut down
■ Low ground pin current at all loads
■ Output voltage accuracy 1% (A Grade)
■ High peak current capability
■ Wide supply voltage range (16V max)
■ Low ZOUT: 0.3Ω typical (10 Hz to 1 MHz)
■ Overtemperature/overcurrent protection
■ −40°C to +125°C junction temperature range
■ Custom voltages available
Applications
■ Cellular Phone
■ Palmtop/Laptop Computer
■ Personal Digital Assistant (PDA)
■ Camcorder, Personal Stereo, Camera
Block Diagram
VIP® is a registered trademark of National Semiconductor Corporation.
© 2010 National Semiconductor Corporation 101295
10129501
www.national.com
1 page  
Symbol
Parameter
Ripple Rejection
IO(SC)
IO(PK)
Short Circuit Current
Peak Output Current
Conditions
f = 1 kHz, CBYPASS = 10 nF
COUT = 10 µF
RL = 0 (Steady State)
(Note 8)
VOUT ≥ Vo(NOM) −5%
LP2985AI-X.X
Typ (Note 6)
Min Max
45
400
350
LP2985I-X.X
(Note 6)
Min Max
Units
dB
mA
mA
Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating
the device outside of its rated operating conditions.
Note 2: The ESD rating of pins 3 and 4 for the SOT-23 package, or pins 5 and 2 for the micro SMD package, is 1 kV.
Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, TJ(MAX), the junction-to-ambient thermal resistance, θJ-
A, and the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperture is calculated using:
Where the value of θJ-A for the SOT-23 package is 220°C/W in a typical PC board mounting. Exceeding the maximum allowable dissipation will cause excessive
die temperature, and the regulator will go into thermal shutdown.
Note 4: If used in a dual-supply system where the regulator load is returned to a negative supply, the LP2985LV output must be diode-clamped to ground.
Note 5: The output PNP structure contains a diode between the VIN to VOUT terminals that is normally reverse-biased. Reversing the polarity from VIN to VOUT
will turn on this diode, and possibly damage the device (See Application Hints).
Note 6: Limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality
Control (SQC) methods. The limits are used to calculate National's Average Outgoing Quality Level (AOQL).
Note 7: The ON/OFF input must be properly driven to prevent possible misoperation. For details, refer to Application Hints.
Note 8: The LP2985LV has foldback current limiting which allows a high peak current when VOUT > 0.5V, and then reduces the maximum output current as
VOUT is forced to ground (see Typical Performance Characteristics curves).
Note 9: VIN must be the greater of 2.2V or VOUT(NOM) + Dropout Voltage to maintain output regulation. Dropout Voltage is defined as the input to output differential
at which the output voltage drops 2% below ther value measured with a 1V differential.
Note 10: Exposing the micro SMD device to direct sunlight will cause misoperation. See Application Hints for additional information.
5 www.national.com
5 Page 
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 ≥ 1 µF is required
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 ≥ 1 µF over the entire operating temperature range.
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 Figure 1 and Figure 2).
10129519
FIGURE 1. LP2985LV 2.2µF Stable ESR Range
10129520
FIGURE 2. LP2985LV 4.7µF Stable ESR Range
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.
11 www.national.com
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LP2985LV.PDF ] | |
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