_______________General Description

The MAX1705/MAX1706 are high-efficiency, low-noise,

step-up DC-DC converters with an auxiliary linear-

regulator output. These devices are intended for use in

battery-powered wireless applications. They use a syn-

chronous rectifier pulse-width-modulation (PWM) boost

topology to generate 2.5V to 5.5V outputs from battery

inputs, such as 1 to 3 NiCd/NiMH cells or 1 Li-Ion cell.

The MAX1705 has an internal 1A N-channel MOSFET

switch. The MAX1706 has a 0.5A switch. Both devices

also have a built-in low-dropout linear regulator that

delivers up to 200mA.

With an internal synchronous rectifier, the MAX1705/

MAX1706 deliver 5% better efficiency than similar non-

synchronous converters. They also feature a pulse-

frequency-modulation (PFM) standby mode to improve

efficiency at light loads, and a 1µA shutdown mode. An

efficiency-enhancing track mode reduces the step-up

DC-DC converter output to 300mV above the linear-reg-

ulator output.

Both devices come in a 16-pin QSOP package, which

occupies the same space as an 8-pin SO. Other features

include two shutdown-control inputs for push-on/push-off

control, and an uncommitted comparator for use as a volt-

age monitor.

________________________Applications

Digital Cordless Phones

PCS Phones

Personal Communicators

Wireless Handsets

Palmtop Computers

Two-Way Pagers

Hand-Held Instruments

____________________________Features

o Up to 96% Efficiency

o Up to 850mA Output (MAX1705)

o Step-Up Output (2.5V to 5.5V adjustable)

o Linear Regulator (1.25V to 5.0V adjustable)

o PWM/PFM Synchronous-Rectified Topology

o 300kHz PWM Mode or Synchronizable

o 1µA Shutdown Mode

o Voltage Monitor

o Pushbutton On/Off Control

1- to 3-Cell, High-Current, Low-Noise,

Step-Up DC-DC Converters with Linear Regulator

________________________________________________________________

Maxim Integrated Products

1

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

LBP

POUT

ONA

ONB

LX

PGND

CLK/SEL

LBO

LDO

TOP VIEW

MAX1705

MAX1706

QSOP

LBN

REF

OUT

TRACK

GND

FB

FBLDO

__________________Pin Configuration

LX

POUT

OUT

STEP-UP OUTPUT

FB

CLK/SEL

ONA

ONB

TRACK

INPUT 0.7V TO 5.5V

PGND

GND

LDO

FBLDO

LBP

LBO

LBN

REF

MAX1705

MAX1706

LINEAR

REGULATOR

OUTPUT

LOW-BATTERY

DETECTION

ON/OFF CONTROL

HIGH

EFFICIENCY

LOW

NOISE

__________Typical Operating Circuit

19-1198; Rev 0; 4/97

PART

MAX1705C/D

MAX1705EEE

MAX1706C/D

0°C to +70°C

-40°C to +85°C

0°C to +70°C

TEMP. RANGE

PIN-PACKAGE

Dice*

16 QSOP

Dice*

EVALUATION

KIT MANUAL

AVAILABLE

______________Ordering Information

*

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

MAX1706EEE

-40°C to +85°C

16 QSOP