Rainbow-electronics MAX849 Manual de usuario descargar pdf (Pagina 1)

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.

For small orders, phone 408-737-7600 ext. 3468.

General Description

The MAX848/MAX849 boost converters set a new stan-

dard of high efficiency and high integration for noise-

sensitive power-supply applications, such as portable

phones and small systems with RF data links. The heart

of the these devices is a synchronous boost-topology

regulator that generates a fixed 3.3V output (or 2.7V to

5.5V adjustable output) from one to three NiCd/NiMH

cells or one Li-Ion cell.

Synchronous rectification provides a 5% efficiency

improvement over similar nonsynchronous boost regu-

lators. In standby mode, pulse-skipping PFM operation

keeps the output voltage alive with only 150µW quies-

cent power consumption. Fixed-frequency PWM opera-

tion ensures that the switching noise spectrum is limited

to the 300kHz fundamental and its harmonics, allowing

easy post-filtering noise reduction. For even tighter

noise spectrum control, synchronize to a 200kHz to

400kHz external clock.

Battery monitoring is provided by a two-channel, volt-

age-to-frequency analog-to-digital converter (ADC).

One channel is intended for a single-cell battery input

(0.625V to 1.875V range), while the other channel is for

monitoring higher voltages (0V to 2.5V range).

Two control inputs are provided for push-on, push-off

control via a momentary pushbutton switch. Upon

power-up, an internal comparator monitors the output

voltage to generate a power-good output (POK).

The devices differ only in the current limit of the

N-channel MOSFET power switch: 0.8A for the

MAX848, and 1.4A for the MAX849.

Features

♦ Up to 95% Efficiency

(see

Typical Output Selector Guide

below)

♦ 3.3V Dual Mode™ or 2.7V to 5.5V Adj. Output

♦ 0.7V to 5.5V Input Range

♦ 0.15mW Standby Mode

♦ 300kHz PWM Mode or Synchronizable

♦ Two-Channel ADC with Serial Output

♦ Power-Good Function

Applications

Digital Cordless Phones PCS Phones

Cellular Phones Hand-Held Instruments

Palmtop Computers Personal Communicators

Local 3.3V to 5V Supplies

MAX848/MAX849

1-Cell to 3-Cell, High-Power,

Low-Noise, Step-Up DC-DC Converters

________________________________________________________________

Maxim Integrated Products

AIN1

AIN2

AINSEL

DATA

ON1

ON2

CLK/SEL

POKIN

OUT

POUT

POK

MAX848

MAX849

OUTPUT

A/D CHANNEL 1 IN

A/D CHANNEL 2 IN

A/D CHANNEL SELECT

A/D OUTPUT

ON/OFF CONTROL

SYNC INPUT

INPUT

0.8V TO 5.5V

VOLTAGE MONITOR

OUTPUT

REF

GND PGND

Typical Operating Circuit

19-1095; Rev 2; 12/97

PART

MAX848ESE

MAX849ESE

-40°C to +85°C

TEMP. RANGE PIN-PACKAGE

16 Narrow SO

Ordering Information

Pin Configuration appears at end of data sheet.

Dual Mode is a trademark of Maxim Integrated Products.

Typical Output Selector Guide

(V)

MAX849 I

OUT

(mA)

MAX848 I

OUT

(mA)

0.9

3.3 100 70

5 70 40

1.2

3.3 300 110

5 200 70

2.4

3.3 750 200

5 500 130

2.7

3.3 800 250

5 600 150

3.6 5 1000 300

1 2 3 4 5 6 ... 15 16

Indice de contenidos

Pagina 1 - 1-Cell to 3-Cell, High-Power

For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.For small orders, phone 408-737-7600 ext. 3468.General

Pagina 2

MAX848/MAX8491-Cell to 3-Cell, High-Power,Low-Noise, Step-Up DC-DC Converters10 ______________________________________________________________________

Pagina 3