MC78BC00 Datasheet, PDF (5/8 Pages) Motorola, Inc – VOLTAGE REGULATOR WITH EXTERNAL POWER TRANSISTOR

MC78BC00 Series
APPLICATIONS INFORMATION
Introduction
The MC78BC00 series of micropower voltage regulators
are specifically designed for ultra–low dropout voltage and an
output current which ranges from several tens of mA to
several hundreds of mA making them ideal for
battery–powered equipment. These regulators also have a
chip enable function which minimizes supply current in
stand–by mode. An input bypass capacitor is recommended
if the regulator is located an appreciable distance (≥ 4 inches)
from the input voltage source. These regulators require a
10 µF capacitance between the output terminal and ground
for stability. Most types of aluminum, tantalum or multilayer
ceramic will perform adequately. Solid tantalums or other
appropriate capacitors are recommended for operation
below 25°C. The bypass capacitors should be mounted with
the shortest possible leads or track lengths directly across
the regulator input and output terminals.
With economical electrolytic capacitors, cold temperature
operation can pose a serious stability problem. As the
electrolyte freezes, around –30°C, the capacitance will
decrease and the equivalent series resistance (ESR) will
increase drastically, causing the circuit to oscillate. Quality
electrolytic capacitors with extended temperature ranges of
–40° to +85°C are readily available. Solid tantalum
capacitors may be the better choice if small size is a
requirement. However, a maximum ESR limit of 3.0 Ω must
be observed over temperature to maintain stability.
Figure 9. Typical Operation
External PNP Transistor
2
In
Vin
Vref
4 Ext
VO
3
RA
Error
Amplifier
RB
Out
10 µF
Gnd
1
CE 5
MOTOROLA ANALOG IC DEVICE DATA
5