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LP2986AIM-3.0 Schematic ( PDF Datasheet ) - National Semiconductor

Teilenummer LP2986AIM-3.0
Beschreibung Micropower/ 200 mA Ultra Low-Dropout Fixed or Adjustable Voltage Regulator
Hersteller National Semiconductor
Logo National Semiconductor Logo 




Gesamt 14 Seiten
LP2986AIM-3.0 Datasheet, Funktion
March 1999
LP2986
Micropower, 200 mA Ultra Low-Dropout Fixed or
Adjustable Voltage Regulator
General Description
The LP2986 is a 200 mA precision LDO voltage regulator
which offers the designer a higher performance version of
the industry standard LP2951.
Using an optimized VIP(Vertically Integrated PNP) pro-
cess, the LP2986 delivers superior performance:
Dropout Voltage: Typically 180 mV @ 200 mA load, and 1
mV @ 1 mA load.
Ground Pin Current: Typically 1 mA @ 200 mA load, and
200 µA @ 10 mA load.
Sleep Mode: The LP2986 draws less than 1 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: The standard product versions available
can be pin-strapped (using the internal resistive divider) to
provide output voltages of 5.0V, 3.3V, or 3.0V with guaran-
teed accuracy of 0.5% (“A” grade) and 1% (standard grade)
at room temperature.
Features
n Ultra low dropout voltage
n Guaranteed 200 mA output current
n SO-8 and mini-SO8 surface mount packages
n <1 µA quiescent current when shutdown
n Low ground pin current at all loads
n 0.5% output voltage accuracy (“A” grade)
n High peak current capability (400 mA typical)
n Wide supply voltage range (16V max)
n Overtemperature/overcurrent protection
n −40˚C to +125˚C junction temperature range
Applications
n Cellular Phone
n Palmtop/Laptop Computer
n Camcorder, Personal Stereo, Camera
Block Diagram
VIPis a trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation DS012935
DS012935-1
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LP2986AIM-3.0 Datasheet, Funktion
Typical Performance Characteristics Unless otherwise specified: TA = 25˚C, COUT = 4.7 µF,
CIN = 2.2 µF, S/D is tied to VIN, VIN = VO(NOM) + 1V, IL = 1 mA.
VOUT vs Temperature
Dropout Voltage vs Temperature
Dropout Voltage vs Load Current
DS012935-8
Dropout Characteristics
DS012935-9
DS012935-10
Ground Pin Current vs Temperature and Load
DS012935-13
Ground Pin Current vs Load Current
DS012935-12
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LP2986AIM-3.0 pdf, datenblatt
Application Hints (Continued)
A lead compensation capacitor (CF) must also be used to
place a zero in the loop response at about 50 kHz. The value
for C F can be found using:
CF = 1/(2π x R1 x 50k)
A good quality capacitor must be used for CF to ensure that
the value is accurate and does not change significantly over
temperature. Mica or ceramic capacitors can be used, as-
suming a tolerance of ±20% or better is selected.
If a ceramic is used, select one with a temperature coeffi-
cient of NPO, COG, Y5P, or X7R. Capacitor types Z5U, Y5V,
and Z4V can not be used because their value varies more
that 50% over the −25˚C to +85˚C temperature range.
SHUTDOWN INPUT OPERATION
The LP2986 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 as VH
and VL, respectively (see Electrical Characteristics).
It is also important that the turn-on (and turn-off) voltage sig-
nals applied to the Shutdown input have a slew rate which is
not less than 40 mV/µs.
CAUTION: the regulator output state can not be guaranteed
if a slow-moving AC (or DC) signal is applied that is in the
range between VH and VL.
REVERSE INPUT-OUTPUT VOLTAGE
The PNP power transistor used as the pass element in the
LP2986 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 LP2986 to 0.3V (see Absolute
Maximum Ratings).
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