_______________General Description

The MAX856–MAX859 are high-efficiency, CMOS, step-

up, DC-DC switching regulators for small, low input volt-

age or battery-powered systems. The MAX856/MAX858

and convert it to a higher, pin-selectable output voltage of

3.3V or 5V. The MAX857/MAX859 adjustable versions

accept 0.8V to 6.0V input voltages and generate higher

adjustable output voltages in the 2.7V to 6.0V range.

Typical efficiencies are greater than 85%. Typical quies-

cent supply current is 25µA (1µA in shutdown).

The MAX856–MAX859 combine ultra-low quiescent supply

current and high efficiency to give maximum battery life. An

internal MOSFET power transistor permits high switching

frequencies. This benefit, combined with internally set peak

inductor current limits, permits the use of small, low-cost

inductors. The MAX856/MAX857 have a 500mA peak

inductor current limit. The MAX858/MAX859 have a 125mA

peak inductor current limit.

________________________Applications

3.3V to 5V Step-Up Conversion

Palmtop Computers

Portable Data-Collection Equipment

Personal Data Communicators/Computers

Medical Instrumentation

2-Cell & 3-Cell Battery-Operated Equipment

Glucose Meters

____________________________Features

o 0.8V to 6.0V Input Supply Voltage

o 0.8V Typ Start-Up Supply Voltage

o 85% Efficiency at 100mA

o 25µA Quiescent Current

o 1µA Shutdown Mode

o 125mA and 500mA Switch-Current Limits Permit

Use of Low-Cost Inductors

o Up to 500kHz Switching Frequency

o ±1.5% Reference Tolerance Over Temperature

o Low-Battery Detector (LBI/LBO)

o 8-Pin SO and µMAX Packages

______________Ordering Information

Ordering Information continued at end of data sheet.

3.3V/5V or Adjustable-Output,

Step-Up DC-DC Converters

________________________________________________________________

Maxim Integrated Products

1

1

2

3

4

8

7

6

5

LX

GND

OUT

LBI

LBO

REF

3/5

SHDN

MAX856

MAX858

SO/

µMAX

TOP VIEW

1

2

3

4

8

7

6

5

LX

GND

OUT

LBI

LBO

REF

FB

SHDN

MAX857

MAX859

SO/

µMAX

__________________Pin Configuration

MAX856

SHDN

3/5

REF

LX

GND

OUT

INPUT

1N5817

OUTPUT

5V AT 100mA

OR

3.3V AT 125mA

LBO

68

µF

47

µH

LOW-BATTERY

DETECTOR OUTPUT

ON/OFF

3V/5V SELECT

LBI

LOW-BATTERY

DETECTOR

INPUT

__________Typical Operating Circuit

19-0211; Rev 4; 5/96

PART

TEMP. RANGE

PIN-PACKAGE

MAX856CSA

0°C to +70°C

8 SO

MAX856CUA

0°C to +70°C

8 µMAX

MAX856C/D

0°C to +70°C

Dice*

MAX856ESA

-40°C to +85°C

8 SO

MAX856MJA

-55°C to +125°C

MAX857CSA

0°C to +70°C

8 SO

MAX857CUA

0°C to +70°C

8 µMAX

MAX857C/D

0°C to +70°C

Dice*

MAX857ESA

-40°C to +85°C

8 SO

MAX857MJA

-55°C to +125°C

EVALUATION

KIT MANUAL

FOLLOWS

DATA

SHEET

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