MAX1549 datasheet(1/35 Pages) MAXIM

Part #	MAX1549

Description	Dual, Interleaved, Fixed-Frequency Step-Down Controller with a Dynamically Adjustable Output

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Manufacturer	MAXIM [Maxim Integrated Products]

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General Description

The MAX1549 dual pulse-width modulation (PWM) step-

down controller provides the high efficiency, excellent

transient response, and high DC-output accuracy nec-

essary for generating low-voltage chipset and RAM

power supplies in notebook computers. The controller

employs a fixed-frequency, current-mode PWM archi-

tecture that does not require complex compensation.

The MAX1549 also interleaves the dual step-down regu-

lators, minimizing the input capacitor requirements.

The MAX1549 features differential current-sense inputs

for accurately sensing the inductor current across an

external current-sense resistor in series with the output

to ensure reliable overload protection. Alternatively, the

controller can provide overload protection using loss-

less inductor current-sensing methods, lowering power

dissipation and reducing system cost.

Single-stage buck conversion allows the MAX1549 to

directly step down high-voltage batteries for the highest

possible efficiency. Very low output-voltage applica-

tions require two-stage conversion—stepping down

from another system supply rail instead of the battery.

The MAX1549 powers chipsets and graphics processor

cores that require dynamically adjustable output voltages,

or generates the active termination bus that must track

the input reference. The main step-down controller

(OUT1) regulates the dedicated reference input (REFIN)

voltage generated by a resistive voltage-divider from the

MAX1549’s reference. The MAX1549 also includes inter-

nal open-drain pulldowns with logic-level control inputs to

dynamically adjust the REFIN resistive-divider ratio. When

a transition occurs on these control inputs, the controller

enters forced-PWM mode and blanks the power-good

(PGOOD1) output and output fault protection. OUT2 uses

a Dual-Mode™ feedback input to provide either fixed

2.5V/1.8V or adjustable output voltage regulation. The

MAX1549 is available in a 40-pin, 6mm x 6mm thin QFN

package.

Applications

Notebook Computers

Dynamically Adjustable Chipset Supplies

Video/GPU Core Supplies

DDR Memory Termination

CPU Core or VCC Supplies

Fixed Chipset/RAM Supplies

Active Termination Buses

Features

♦ Interleaved, Fixed-Frequency, Current-Mode

Control Architecture

♦ 1% VOUT Accuracy Over Line and Load

♦ Main Output (OUT1)

0.5V to 2.0V Adjustable Output

External Reference Input for Dynamically

Selectable Output Voltages

Four Digitally Selectable Output Voltages

Power-Good and Fault Blanking During

Transitions

♦ Second Output (OUT2)

2.5V/1.8V Fixed or 0.5V to 2.7V Adjustable

Output

♦ Accurate Differential Current-Sense Inputs

♦ 100kHz/200kHz/300kHz/400kHz Selectable

Switching Frequency

♦ Output Overvoltage/Undervoltage Protection

♦ Soft-Start and Soft-Shutdown

♦ Drives Large Synchronous-Rectifier FETs

♦ 2V ±0.6% Reference Output

♦ Separate Enable Inputs with Accurate Threshold

Voltages

♦ Separate Power-Good Window Comparators

Dual, Interleaved, Fixed-Frequency Step-Down

Controller with a Dynamically Adjustable Output

________________________________________________________________ Maxim Integrated Products

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FBLANK

MAX1549

THIN QFN

6mm x 6mm

TOP VIEW

LX1

BST1

SKIP

DL1

VDD

N.C.

DL2

PGND

BST2

LX2

G1

G0

ILIM2

ILIM1

CC1

VCC

REF

N.C.

GND

Pin Configuration

Ordering Information

19-3165; Rev 0; 1/04

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

PART

TEMP RANGE

PIN-PACKAGE

MAX1549ETL

-40°C to +85°C

40 Thin QFN 6mm x 6mm

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

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