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PDF LP2981AIM5-2.5 Data sheet ( Hoja de datos )
| Número de pieza | LP2981AIM5-2.5 | |
| Descripción | Micropower 100 mA Ultra Low-Dropout Regulator | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LP2981AIM5-2.5 (archivo pdf) en la parte inferior de esta página. Total 16 Páginas | ||
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March 2000
LP2981
Micropower 100 mA Ultra Low-Dropout Regulator
General Description
The LP2981 is a 100 mA, fixed-output voltage regulator de-
signed specifically to meet the requirements of
battery-powered applications.
Using an optimized VIP™ (Vertically Integrated PNP) pro-
cess, the LP2981 delivers unequaled performance in all
specifications critical to battery-powered designs:
Dropout Voltage. Typically 200 mV @ 100 mA load, and
7 mV @ 1 mA load.
Ground Pin Current. Typically 600 µA @ 100 mA load, and
80 µA @ 1 mA load.
Sleep Mode. Less than 1 µA quiescent current when ON/
OFF pin is pulled low.
Smallest Possible Size. SOT-23and micro SMD packages
use an absolute minimum board space.
Precision Output. 0.75% tolerance output voltages avail-
able (A grade).
Eleven voltage options, from 2.5V to 5.0V, are available as
standard products.
Features
n Ultra low dropout voltage
n Output voltage accuracy 0.75% (A Grade)
n Guaranteed 100 mA output current
n Smallest possible size (SOT-23, micro SMD package)
n < 1 µA quiescent current when shutdown
n Low ground pin current at all load currents
n High peak current capability (300 mA typical)
n Wide supply voltage range (16V max)
n Fast dynamic response to line and load
n Low ZOUT over wide frequency range
n Overtemperature/overcurrent protection
n −40˚C to +125˚C junction temperature range
Applications
n Cellular Phone
n Palmtop/Laptop Computer
n Personal Digital Assistant (PDA)
n Camcorder, Personal Stereo, Camera
Block Diagram
DS012506-1
VIP™ is a trademark of National Semiconductor Corporation.
© 2000 National Semiconductor Corporation DS012506
www.national.com
1 page  
Electrical Characteristics (Continued)
Note 1: Absolute maximum ratings indicate limits beyond which damage to the component may occur. Electrical specifications do not apply when operating the de-
vice outside of its rated operating conditions.
Note 2: The ESD rating of pins 3 and 4 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, θJA, and
the ambient temperature, TA. The maximum allowable power dissipation at any ambient temperature is calculated using:
The value of θJA for the SOT-23 package is 220˚C/W and the micro SMD package is 320˚C/W. Exceeding the maximum allowable power dissipation will cause ex-
cessive 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 LP2981 output must be diode-clamped to ground.
Note 5: The output PNP structure contains a diode between the VIN and VOUT terminals that is normally reverse-biased. Reversing the polarity from VIN to VOUT
will turn on this diode (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: Dropout voltage is defined as the input to output differential at which the output voltage drops 100 mV below the value measured with a 1V differential.
Note 8: The ON/OFF inputs must be properly driven to prevent misoperation. For details, refer to Application Hints.
Note 9: See Typical Performance Characteristics curves.
Basic Application Circuit
DS012506-4
*ON/OFF input must be actively terminated. Tie to VIN if this function is not to be used.
**Minimum Output Capacitance is shown to insure stability over full load current range. More capacitance provides superior dynamic performance and
additional stability margin (see Application Hints).
***Do not make connections to this pin.
5 www.national.com
5 Page 
Typical Performance Characteristics Unless otherwise specified: TA = 25˚C, VIN = VO(NOM) + 1V,
COUT = 4.7 µF, CIN = 1 µF all voltage options, ON/OFF pin tied to VIN. (Continued)
ON/OFF Pin Current vs
VON/OFF
ON/OFF Threshold
vs Temperature
Application Hints
DS012506-36
EXTERNAL CAPACITORS
Like any low-dropout regulator, the external capacitors used
with the LP2981 must be carefully selected to assure regula-
tor loop stability.
INPUT CAPACITOR: An input capacitor whose value is
≥ 1 µF is required with the LP2981 (amount of capacitance
can be increased without limit).
This capacitor must be located a distance of not more than
0.5" from the input pin of the LP2981 and returned to a clean
analog ground. Any good quality ceramic or tantalum can be
used for this capacitor.
OUTPUT CAPACITOR: The output capacitor must meet
both the requirement for minimum amount of capacitance
and E.S.R. (equivalent series resistance) value. Curves are
provided which show the allowable ESR range as a function
of load current for various output voltages and capacitor val-
ues (refer to Figures 1, 2, 3, 4).
IMPORTANT: The output capacitor must maintain its ESR in
the stable region over the full operating temperature range to
assure stability. Also, capacitor tolerance and variation with
temperature must be considered to assure the minimum
amount of capacitance is provided at all times.
This capacitor should be located not more than 0.5" from the
output pin of the LP2981 and returned to a clean analog
ground.
CAPACITOR CHARACTERISTICS
TANTALUM: Tantalum capacitors are the best choice for
use with the LP2981. Most good quality tantalums can be
used with the LP2981, but check the manufacturer’s data
sheet to be sure the ESR is in range.
It is important to remember that ESR increases at lower tem-
peratures and a capacitor that is near the upper limit for sta-
bility at room temperature can cause instability when it gets
cold.
In applications which must operate at very low temperatures,
it may be necessary to parallel the output tantalum capacitor
with a ceramic capacitor to prevent the ESR from going up
too high (see next section for important information on ce-
ramic capacitors).
DS012506-37
CERAMIC: Ceramic capacitors are not recommended for
use at the output of the LP2981. This is because the ESR of
a ceramic can be low enough to go below the minimum
stable value for the LP2981. A 2.2 µF ceramic was measured
and found to have an ESR of about 15 mΩ, which is low
enough to cause oscillations.
If a ceramic capacitor is used on the output, a 1Ω resistor
should be placed in series with the capacitor.
ALUMINUM: Because of large physical size, aluminum elec-
trolytics are not typically used with the LP2981. They must
meet the same ESR requirements over the operating tem-
perature range, more difficult because of their steep increase
at cold temperature.
An aluminum electrolytic can exhibit an ESR increase of as
much as 50X when going from 20˚C to −40˚C. Also, some
aluminum electrolytics are not operational below −25˚C be-
cause the electrolyte can freeze.
DS012506-38
FIGURE 1. 5V/3.3 µF ESR Curves
11 www.national.com
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LP2981AIM5-2.5.PDF ] | |
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