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________________General Description

The MAX1630–MAX1635 are buck-topology, step-down,

switch-mode, power-supply controllers that generate

logic-supply voltages in battery-powered systems. These

high-performance, dual/triple-output devices include on-

board power-up sequencing, power-good signaling with

delay, digital soft-start, secondary winding control, low-

dropout circuitry, internal frequency-compensation net-

works, and automatic bootstrapping.

Up to 96% efficiency is achieved through synchronous

rectification and Maxim’s proprietary Idle Mode™ control

scheme. Efficiency is greater than 80% over a 1000:1

load-current range, which extends battery life in system-

suspend or standby mode. Excellent dynamic response

corrects output load transients caused by the latest

dynamic-clock CPUs within five 300kHz clock cycles.

Strong 1A on-board gate drivers ensure fast external

N-channel MOSFET switching.

These devices feature a logic-controlled and synchroniz-

able, fixed-frequency, pulse-width-modulation (PWM)

operating mode. This reduces noise and RF interference

in sensitive mobile communications and pen-entry appli-

cations. Asserting the SKIP pin enables fixed-frequency

mode, for lowest noise under all load conditions.

The MAX1630–MAX1635 include two PWM regulators,

adjustable from 2.5V to 5.5V with fixed 5.0V and 3.3V

modes. All these devices include secondary feedback

regulation, and the MAX1630/MAX1632/MAX1633/

MAX1635 each contain 12V/120mA linear regulators. The

MAX1631/MAX1634 include a secondary feedback input

(SECFB), plus a control pin (STEER) that selects which

PWM (3.3V or 5V) receives the secondary feedback sig-

nal. SECFB provides a method for adjusting the sec-

ondary winding voltage regulation point with an external

resistor divider, and is intended to aid in creating auxiliary

voltages other than fixed 12V.

The MAX1630/MAX1631/MAX1632 contain internal out-

put overvoltage and undervoltage protection features.

________________________Applications

Notebook and Subnotebook Computers

PDAs and Mobile Communicators

Desktop CPU Local DC-DC Converters

____________________________Features

o 96% Efficiency

o +4.2V to +30V Input Range

o 2.5V to 5.5V Dual Adjustable Outputs

o Selectable 3.3V and 5V Fixed or Adjustable

Outputs (Dual Mode™)

o 12V Linear Regulator

o Adjustable Secondary Feedback

(MAX1631/MAX1634)

o 5V/50mA Linear Regulator Output

o Precision 2.5V Reference Output

o Programmable Power-Up Sequencing

o Power-Good (RESET) Output

o Output Overvoltage Protection

(MAX1630/MAX1631/MAX1632)

o Output Undervoltage Shutdown

(MAX1630/MAX1631/MAX1632)

o 200kHz/300kHz Low-Noise, Fixed-Frequency

Operation

o Low-Dropout, 99% Duty-Factor Operation

o 2.5mW Typical Quiescent Power (+12V input, both

SMPSs on)

o 4µA Typical Shutdown Current

o 28-Pin SSOP Package

Multi-Output, Low-Noise Power-Supply

Controllers for Notebook Computers

________________________________________________________________

Maxim Integrated Products

1

5V

LINEAR

12V

LINEAR

POWER-UP

SEQUENCE

POWER-

GOOD

3.3V

SMPS

5V

SMPS

RESET

ON/OFF

+5V (RTC)

+3.3V

INPUT

+5V

+12V

________________Functional Diagram

19-0480; Rev 3; 4/97

PART

MAX1630CAI

MAX1630EAI

-40°C to +85°C

0°C to +70°C

TEMP. RANGE

PIN-PACKAGE

28 SSOP

28 SSOP

EVALUATION

KIT

AVAILABLE

_______________Ordering Information

Ordering Information continued on last page.

Pin Configurations and Selector Guide appear at end of data

sheet.

Idle Mode and Dual Mode are trademarks of Maxim Integrated

Products.