3A, 1MHz, Low-Voltage, Step-Down Regulators with

Synchronous Rectification and Internal Switches

________________________________________________________________ Maxim Integrated Products

1

19-2198; Rev 0; 10/01

General Description

The MAX1830/MAX1831 constant-off-time, pulse-width-

modulated (PWM) step-down DC-DC converters are

ideal for use in 5V and 3.3V to low-voltage conversion

necessary in notebook and subnotebook computers.

These devices feature internal synchronous rectification

for high efficiency and reduced component count. They

require no external Schottky diode. The internal 45m

Ω

PMOS power switch and 55m

Ω NMOS synchronous-rec-

tifier switch easily deliver continuous load currents up to

3A. The MAX1830 produces preset +2.5V, +1.8V, or

+1.5V output voltage or an adjustable output from +1.1V

+1.5V output voltages and an adjustable output from

The MAX1830/MAX1831 use a unique current-mode,

constant-off-time, PWM control scheme, which includes

Idle Mode™ to maintain high efficiency during light-

load operation. The programmable constant-off-time

architecture sets switching frequencies up to 1MHz,

allowing the user to optimize performance trade-

offs between efficiency, output switching noise, compo-

nent size, and cost. Both devices are designed for con-

tinuous output currents up to 3A, an internal digital

soft-start to limit surge currents during startup, a 100%

duty cycle mode for low-dropout operation, and a

low-power shutdown mode that disconnects the input

from the output and reduces supply current below

1µA.The MAX1830/MAX1831 are available in 16-pin

QSOP packages.

For similar devices that provide continuous output

currents of 1A to 3A, refer to the MAX1644, MAX1623,

and MAX1742/MAX1842/MAX1843 data sheets.

Applications

5V or 3.3V to Low-Voltage Conversion

CPU I/O Supplies

Chipset Supplies

Notebook and Subnotebook Computers

Features

o ±1.5% Output Accuracy

o 94% Efficiency

o Internal PMOS/NMOS Switches

45m

50m

o Output Voltages

+3.3V, +2.5V, or +1.5V Pin Selectable (MAX1831)

+2.5V, +1.8V, or +1.5V Pin Selectable (MAX1830)

o +3V to +5.5V Input Voltage Range

o 750µA (max) Operating Supply Current

o <1µA Shutdown Supply Current

o Programmable Constant-Off-Time Operation

o Up to 1MHz Switching Frequency

o Idle Mode Operation at Light Loads

o Thermal Shutdown

o Internal Digital Soft-Start Inrush Current Limiting

o 100% Duty Cycle During Low-Dropout Operation

o Output Short-Circuit Protection

o 16-Pin QSOP Package

Idle Mode is a trademark of Maxim Integrated Products, Inc.

Typical Configuration

TOFF

COMP

FBSEL

SHDN

IN

PGND

GND

REF

LX

FB

MAX1830

MAX1831

OUTPUT

+1.1V TO

INPUT

+3V TO

+5.5V

EVALUATION

KIT

AVAILABLE

Pin Configuration appears at end of data sheet.

PART

MAX1830EEE

-40°C to +85°C

TEMP. RANGE

PIN-PACKAGE

16 QSOP

Ordering Information

MAX1831EEE

-40°C to +85°C

16 QSOP

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.