1FEATURES
2• Ultra Low Dropout Voltage (100mV at 0.8A typ)
• Low Ground Pin Current
• Load Regulation of 0.04%/A
• 60 nA Typical Quiescent Current in Shutdown
• 1.5% Output Accuracy (25°C)
• TO-220, DDPAK/TO-263 and SO PowerPAD-8
Packages
• Over Temperature/Over Current Protection
• −40°C to +125°C Junction Temperature Range

APPLICATIONS
• DSP Power Supplies
• Server Core and I/O Supplies
• PC Add-in-Cards
• Local Regulators in Set-Top Boxes
• Microcontroller Power Supplies
• High Efficiency Power Supplies
• SMPS Post-Regulators

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 regulators, the
CMOS architecture consumes extremely low
quiescent current at any output load current. The use of an N-MOS power transistor results in wide
bandwidth, yet minimum external capacitance is
required to maintain loop stability.
The fast transient response of these devices makes
them suitable for use in powering DSP,
Microcontroller Core voltages and Switch Mode
Power Supply post regulators. The parts are available
in TO-220, DDPAK/TO-263 and SO PowerPAD-8
packages.
Dropout Voltage: 100 mV (typ) at 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
accuracy.