LP3891 Datasheet, PDF (1/12 Pages) National Semiconductor (TI) – 0.8A Fast-Response Ultra Low Dropout Linear

September 2003
LP3891
0.8A Fast-Response Ultra Low Dropout Linear
Regulators
General Description
The LP3891 is a high current, fast response regulator which
can maintain output voltage regulation with minimum input to
output voltage drop. Fabricated on a CMOS process, the
device operates from two input voltages: Vbias provides
voltage to drive the gate of the N-MOS power transistor,
while Vin is the input voltage which supplies power to the
load. The use of an external bias rail allows the part to
operate from ultra low Vin voltages. Unlike bipolar regula-
tors, the CMOS architectutre consumes extremely low qui-
escent current at any output load current. The use of an
N-MOS power transistor results in wide bandwidth, yet mini-
mum external capacitance is required to maintain loop sta-
bility.
The fast transient response of these devices makes them
suitable for use in powering DSP, Microcontroller Core volt-
ages and Switch Mode Power Supply post regulators. The
parts are available in TO-220 and TO-263 packages.
Dropout Voltage: 100 mV (typ) @ 0.8A load current.
Ground Pin Current: 3 mA (typ) at full load.
Shutdown Current: 60 nA (typ) when S/D pin is low.
Precision Output Voltage: 1.5% room temperature accu-
racy.
Features
n Ultra low dropout voltage (100mV @ 0.8A typ)
n Low ground pin current
n Load regulation of 0.04%/A
n 60 nA typical quiescent current in shutdown
n 1.5% output accuracy (25˚C)
n TO-220, TO-263 packages
n Over temperature/over current protection
n −40˚C to +125˚C junction temperature range
Applications
n DSP Power Supplies
n Server Core and I/O Supplies
n PC Add-in-Cards
n Local Regulators in Set-Top Boxes
n Microcontroller Power Supplies
n High Efficiency Power Supplies
n SMPS Post-Regulators
Typical Application Circuit
20069501
At least 10 µF of input and output capacitance is required for stability.
*Tantalum capacitors are recommended. Aluminum electrolytic capacitors may be used for restricted temperature range. See application hints.
Connection Diagrams
TO-220, Top View
20069502
© 2003 National Semiconductor Corporation DS200695
20069503
TO-263, Top View
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