MC78BC33NTR 查看數據表（PDF） - Motorola => Freescale

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MC78BC33NTR

Micropower Voltage Regulator

Motorola => Freescale 

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

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