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General Description

The MAX1684/MAX1685 are high-efficiency, internal-

switch, PWM step-down switching regulators intended to

power cellular phones, communicating PDAs, and

handy-terminals. These devices deliver a guaranteed 1A

output current from two Li-Ion batteries. Their wide input

voltage range of 2.7V to 14V gives design flexibility and

allows batteries to charge from a wall cube, since the ICs

operate at the higher voltages that occur when the bat-

tery is removed. The output voltage is preset to 3.3V or

The low-on-resistance power switch and built-in synchro-

nous rectifier provide high efficiencies of up to 96%.

There are four modes of operation: fixed-frequency

mode, normal mode, low-power mode, and shutdown

mode. The fixed-frequency PWM mode of operation

offers excellent noise characteristics. The normal mode

maintains high efficiency at all loads. The low-power

mode is used to conserve power in standby or when full

load is not required. The shutdown mode is used to

power down the device for minimal current draw.

The MAX1684 runs at 300kHz for applications that

require highest efficiency. The MAX1685 runs at

600kHz to allow use of smaller external components.

These devices can also be synchronized to an external

clock. Other features include a 100% duty cycle for

low-dropout applications, an auxiliary 3V/5mA output,

and a 1% accurate reference.

Both devices are available in a space-saving 16-QSOP

package. An evaluation kit is also available to help

speed designs. For a similar device in a 10-pin µMAX

package with lower input voltage requirements (5.5V

max), see the MAX1692 data sheet.

Applications

Cellular Phones

2-Way Radios and Walkie-Talkies

Computer Peripherals

Personal Communicators

PDAs and Handy-Terminals

Features

o Up to 96% Efficiency

o 1A Guaranteed Output Current

o 100% Duty Cycle in Dropout

o 2.7V to 14V Input Range (15V absolute max)

o ±1% Accurate Reference Output

o 0.24

Ω P-Channel On-Resistance

o Synchronizable Switching Frequency

o Fixed-Frequency PWM Operation

300kHz (MAX1684)

600kHz (MAX1685)

o 150µA Normal Mode Quiescent Current

o 25µA Low-Power Mode Quiescent Current

o 2µA Shutdown Current

o Dual Mode™ Fixed 3.3V (±1%) Output or

o Small 16-QSOP Package

o Auxiliary Output (CVL): 3V/5mA

Low-Noise, 14V Input, 1A, PWM

Step-Down Converters

________________________________________________________________

Maxim Integrated Products

1

MAX1684

MAX1685

LX

IN

AIN

GND

OUTPUT

3.3V AT 1A

INPUT

2.7V TO 14V

BOOT

SHDN

CVH

CVL

STBY

SYNC/PWM

FB

CC

REF

+

+

19-1454; Rev 0; 4/99

PART

MAX1684EEE

MAX1685EEE

-40°C to +85°C

-40°C to +85°C

TEMP. RANGE

PIN-PACKAGE

16 QSOP

16 QSOP

EVALUATION

KIT MANUAL

FOLLOWS

DATA

SHEET

Typical Operating Circuit

Ordering Information

Pin Configuration appears at end of data sheet.

Dual Mode is a trademark of Maxim Integrated Products.