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PDF LP2989IMX-2.5 Data sheet ( Hoja de datos )
| Número de pieza | LP2989IMX-2.5 | |
| Descripción | Micropower/Low Noise/ 500 mA Ultra Low-Dropout Regulator For Use with Ceramic Output Capacitors | |
| Fabricantes | National Semiconductor | |
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March 2000
LP2989
Micropower/Low Noise, 500 mA Ultra Low-Dropout
Regulator
For Use with Ceramic Output Capacitors
General Description
The LP2989 is a fixed-output 500 mA precision LDO regula-
tor designed for use with ceramic output capacitors.
Output noise can be reduced to 18µV (typical) by connecting
an external 10 nF capacitor to the bypass pin.
Using an optimized VIP™ (Vertically Integrated PNP) pro-
cess, the LP2989 delivers superior performance:
Dropout Voltage: Typically 310 mV @ 500 mA load, and 1
mV @ 100 µA load.
Ground Pin Current: Typically 3 mA @ 500 mA load, and
110 µA @ 100 µA load.
Sleep Mode: The LP2989 draws less than 0.8 µA quiescent
current when shutdown pin is pulled low.
Error Flag: The built-in error flag goes low when the output
drops approximately 5% below nominal.
Precision Output: Guaranteed output voltage accuracy is
0.75% (“A” grade) and 1.25% (standard grade) at room tem-
perature.
Features
n Ultra low dropout voltage
n Guaranteed 500 mA continuous output current
n Very low output noise with external capacitor
n SO-8 surface mount package
n <0.8 µA quiescent current when shutdown
n Low ground pin current at all loads
n 0.75% output voltage accuracy (“A” grade)
n High peak current capability (800 mA typical)
n Wide supply voltage range (16V max)
n Overtemperature/overcurrent protection
n −40˚C to +125˚C junction temperature range
Applications
n Notebook/Desktop PC
n PDA/Palmtop Computer
n Wireless Communication Terminals
n SMPS Post-Regulator
Block Diagram
VIP™ is a trademark of National Semiconductor Corporation.
© 2000 National Semiconductor Corporation DS101339
DS101339-1
www.national.com
1 page  
Typical Performance Characteristics Unless otherwise specified: TA = 25˚C, COUT = 4.7 µF,
CIN = 1 µF, S/D is tied to VIN, VIN = VO(NOM) + 1V, IL = 1 mA, VOUT = 2.5V.
Input Current vs VIN
Input Current vs VIN
IGND vs Shutdown
DS101339-5
IGND vs Shutdown
DS101339-6
IGND vs Shutdown
DS101339-7
IGND vs Shutdown
DS101339-8
DS101339-9
5
DS101339-10
www.national.com
5 Page 
Application Hints (Continued)
est of the three types listed, their capacitance is very stable
with temperature, and DC leakage currrent is extremely low.
One disadvantage is that film capacitors are larger in physi-
cal size than ceramic or tantalum which makes film a poor
choice for either input or output capacitors.
However, their low leakage makes them a good choice for
the noise bypass capacitor. Since the required amount of ca-
pacitance is only .01 µF, small surface-mount film capacitors
are avalable in this size.
SHUTDOWN INPUT OPERATION
The LP2989 is shut off by driving the Shutdown input low,
and turned on by pulling it high. If this feature is not to be
used, the Shutdown input should be tied to VIN to keep the
regulator output on at all times.
To assure proper operation, the signal source used to drive
the Shutdown input must be able to swing above and below
the specified turn-on/turn-off voltage thresholds listed in the
Electrical Characteristics section under VON/OFF.
To prevent mis-operation, the turn-on (and turn-off) voltage
signals applied to the Shutdown input must have a slew rate
which is ≥ 40 mV/µs.
CAUTION: the regulator output voltage can not be guaran-
teed if a slow-moving AC (or DC) signal is applied that is in
the range between the specified turn-on and turn-off volt-
ages listed under the electrical specification VON/OFF (see
Electrical Characteristics).
REVERSE INPUT-OUTPUT VOLTAGE
The PNP power transistor used as the pass element in the
LP2989 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 such cases, a parasitic SCR can latch which will allow a
high current to flow into VIN (and out the ground pin), which
can damage the part.
In any application where the output may be pulled above the
input, an external Schottky diode must be connected from
VIN to VOUT (cathode on VIN, anode on VOUT), to limit the re-
verse voltage across the LP2989 to 0.3V (see Absolute
Maximum Ratings).
11 www.national.com
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet LP2989IMX-2.5.PDF ] | |
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