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MAX1742/MAX1842

1A/2.7A, 1MHz, Step-Down Regulators with

Synchronous Rectification and Internal Switches

________________________________________________________________ Maxim Integrated Products 1

19-1760; Rev 1; 2/02

General Description

The MAX1742/MAX1842 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 neces-

sary 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 90mΩ PMOS

power switch and 70mΩ NMOS synchronous-rectifier

switch easily deliver continuous load currents up to 1A.

The MAX1742/MAX1842 produce a preset 2.5V, 1.8V, or

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

. They achieve efficiencies as high as 95%.

The MAX1742/MAX1842 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 architec-

ture sets switching frequencies up to 1MHz, allowing the

user to optimize performance trade-offs between effi-

ciency, output switching noise, component size, and

cost. Both devices are designed for continuous output

currents up to 1A. The MAX1742 uses a peak current

limit of 1.3A (min) and is suitable for applications requir-

ing small external component size and high efficiency.

The MAX1842 has a higher current limit of 3.1A (min)

and is intended for applications requiring an occasional

burst of output current up to 2.7A. Both devices also fea-

ture an adjustable soft-start to limit surge currents during

startup, a 100% duty cycle mode for low-dropout opera-

tion, and a low-power shutdown mode that disconnects

the input from the output and reduces supply current

below 1µA. The MAX1742/MAX1842 are available in 16-

pin QSOP packages.

For similar devices that provide continuous output cur-

rents up to 2A and 3A, refer to the MAX1644 and

MAX1623 data sheets.

Applications

5V or 3.3V to Low-Voltage Conversion

CPU I/O Ring

Chipset Supplies

Notebook and Subnotebook Computers

Features

♦ ±1% Output Accuracy

♦ 95% Efficiency

♦ Internal PMOS and NMOS Switches

90mΩ On-Resistance at V

= 4.5V

110mΩ On-Resistance at V

= 3V

♦ Output Voltage

2.5V, 1.8V, or 1.5V Pin Selectable

1.1V to V

Adjustable

♦ 3V to 5.5V Input Voltage Range

♦ 600µA (max) Operating Supply Current

♦ <1µA Shutdown Supply Current

♦ Programmable Constant-Off-Time Operation

♦ 1MHz (max) Switching Frequency

♦ Idle-Mode Operation at Light Loads

♦ Thermal Shutdown

♦ Adjustable Soft-Start Inrush Current Limiting

♦ 100% Duty Cycle During Low-Dropout Operation

♦ Output Short-Circuit Protection

♦ 16-Pin QSOP Package

PART

MAX1742EEE

-40°C to +85°C

TEMP RANGE PIN-PACKAGE

16 QSOP

Ordering Information

Idle Mode is a trademark of Maxim Integrated Products.

Typical Configuration

TOFF

COMP

FBSEL

SHDN

PGND

GND

REF

MAX1742

MAX1842

OUTPUT

1.1V TO

INPUT

3V TO

5.5V

0.01µF

1µF

2.2µF

470pF

10Ω

MAX1842EEE

-40°C to +85°C 16 QSOP

Pin Configuration appears at end of data sheet.

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.

EVALUATION KIT

AVAILABLE

1 2 3 4 5 6 ... 15 16

MAX1742/MAX1842 1

Indice de contenidos

Pagina 1 - MAX1742/MAX1842

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches________________________________________________

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MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches10 _____________________________________________

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MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches________________________________________________

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MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches12 _____________________________________________

Pagina 5

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches________________________________________________

Pagina 6

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches14 _____________________________________________

Pagina 7

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches________________________________________________

Pagina 8

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal SwitchesMaxim cannot assume responsibility for use of an

Pagina 9

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches2 ______________________________________________

Pagina 10

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches________________________________________________

Pagina 11

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches4 ______________________________________________

Pagina 12

Typical Operating Characteristics(Circuit of Figure 1, TA = +25°C, unless otherwise noted.)MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSync

Pagina 13

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches6 ______________________________________________

Pagina 14

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches________________________________________________

Pagina 15

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches8 ______________________________________________

Pagina 16

MAX1742/MAX18421A/2.7A, 1MHz, Step-Down Regulators withSynchronous Rectification and Internal Switches________________________________________________

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