General Description

The MAX1765 is a high-efficiency, low-noise, step-up

DC-DC converter intended for use in battery-powered

wireless applications. This device operates at a high

1MHz fixed frequency while maintaining an exception-

ally low quiescent supply current (200µA). Its small

external components and tiny package make this

device an excellent choice for small hand-held applica-

tions that require the longest possible battery life.

The MAX1765 uses a synchronous-rectified pulse-

width-modulation (PWM) boost topology to generate

2.5V to 5.5V outputs from a wide range of input

sources, such as one to three alkaline or NiCd/NiMH

cells or a single lithium-ion (Li+) cell. Maxim's propri-

etary architecture significantly improves efficiency at

low load currents while automatically transitioning to

fixed-frequency PWM operation at medium to high load

currents to maintain excellent full-load efficiency.

Forced-PWM mode is available for applications that

require constant-frequency operation at all load cur-

rents, and the MAX1765 may also be synchronized to

an external clock to protect sensitive frequency bands

in communications equipment.

The MAX1765’s low-dropout (LDO) linear regulator and

DC-DC converter have separate shutdown control. The

linear regulator's 250m

Ω pass device maintains excel-

lent dropout voltage at currents up to 500mA. The

MAX1765 also features analog soft-start and current-

limit functions to permit optimization of efficiency, exter-

nal component size, and output voltage ripple.

The MAX1765 comes in a 16-pin QSOP package and a

thermally enhanced 16-pin TSSOP-EP.

____________________________Features

o High-Efficiency Step-Up Converter

Up to 93% Efficiency

Adjustable Output from +2.5V to +5.5V

Up to 800mA Output

PWM Synchronous-Rectified Topology

1MHz Operating Frequency (or Sync)

o LDO Linear Regulator

500mA LDO Linear Regulator

2.85V Linear Regulator Output or Adjustable

(1.25V to 5V)

Low 125mV Dropout at 500mA

o +0.7V to +5.5V Input Range

o 0.1µA Logic-Controlled Shutdown

o Adjustable Inductor Current Limit and Soft-Start

o Thermal Shutdown

o 1.5W, 16-Pin TSSOP-EP Package Available

800mA, Low-Noise, Step-Up DC-DC Converter

with 500mA Linear Regulator

________________________________________________________________ Maxim Integrated Products

1

19-1805; Rev 0; 12/00

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

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15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

FBL

ONL

TRACK

INL

POUT

LX

PGND

OUTL

TOP VIEW

MAX1765

QSOP/TSSOP-EP

ONB

ISET

REF

OUT

GND

FB

ONA

CLK/SEL

Pin Configuration

Wireless Handsets

PCS Phones

Palmtop Computers

Personal

Communicators

Hand-Held Instruments

Portable Audio Players

Applications

FBL

REF

ILIM

ONL

ONA

µH

OUTL = 2.85V

(ADJ 1.25V

TO 5V)

OUT = 3.3V

OUT

OUTL

POUT

FB

GND

PGND

TRACK

LX

CLK/SEL

ONB

INL

MAX1765

Typical Operating Circuit

Ordering Information

*Exposed pad

PART

TEMP. RANGE

PIN-PACKAGE

MAX1765EEE

-40

°C to +85°C

16 QSOP

MAX1765EUE

-40

°C to +85°C

16 TSSOP-EP*