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MAX1717

Dynamically Adjustable, Synchronous Step-Down Controller for Notebook CPUs

Maxim Integrated 

19-1636; Rev 3; 8/05

EVAALVUAAILTAIOBNLEKIT Dynamically Adjustable, Synchronous

Step-Down Controller for Notebook CPUs

General Description

The MAX1717 step-down controller is intended for core

CPU DC-DC converters in notebook computers. It fea-

tures a dynamically adjustable output, ultra-fast tran-

sient response, high DC accuracy, and high efficiency

needed for leading-edge CPU core power supplies.

Maxim’s proprietary Quick-PWM™ quick-response,

constant-on-time PWM control scheme handles wide

input/output voltage ratios with ease and provides

100ns “instant-on” response to load transients while

maintaining a relatively constant switching frequency.

The output voltage can be dynamically adjusted

through the 5-bit digital-to-analog converter (DAC)

inputs over a 0.925V to 2V range. A unique feature of

the MAX1717 is an internal multiplexer (mux) that

accepts two 5-bit DAC settings with only five digital

input pins. Output voltage transitions are accomplished

with a proprietary precision slew-rate control† that mini-

mizes surge currents to and from the battery while

guaranteeing “just-in-time” arrival at the new DAC setting.

High DC precision is enhanced by a two-wire remote-

sensing scheme that compensates for voltage drops in

the ground bus and output voltage rail. Alternatively,

the remote-sensing inputs can be used together with

the MAX1717’s high DC accuracy to implement a volt-

age-positioned circuit that modifies the load-transient

response to reduce output capacitor requirements and

full-load power dissipation.

Single-stage buck conversion allows these devices to

directly step down high-voltage batteries for the highest

possible efficiency. Alternatively, two-stage conversion

(stepping down the +5V system supply instead of the

battery) at a higher switching frequency allows the mini-

mum possible physical size.

The MAX1717 is available in a 24-pin QSOP package.

Applications

Notebook Computers with SpeedStep™ or

Other Dynamically Adjustable Processors

2-Cell to 4-Cell Li+ Battery to CPU Core Supply

Converters

5V to CPU Core Supply Converters

Pin Configuration appears at end of data sheet.

†P.

Quick-PWM is a trademark of Maxim Integrated Products.

SpeedStep is a trademark of Intel Corp.

Features

♦ Quick-PWM Architecture

♦ ±1% VOUT Accuracy Over Line and Load

♦ 5-Bit On-Board DAC with Input Mux

♦ Precision-Adjustable VOUT Slew Control

♦ 0.925V to 2V Output Adjust Range

♦ Supports Voltage-Positioned Applications

♦ 2V to 28V Battery Input Range

♦ Requires a Separate +5V Bias Supply

♦ 200/300/550/1000kHz Switching Frequency

♦ Over/Undervoltage Protection

♦ Drives Large Synchronous-Rectifier FETs

♦ 700µA (typ) ICC Supply Current

♦ 2µA (typ) Shutdown Supply Current

♦ 2V ±1% Reference Output

♦ VGATE Transition-Complete Indicator

♦ Small 24-Pin QSOP Package

Ordering Information

PART

TEMP RANGE

MAX1717EEG

-40°C to +85°C

MAX1717EEG+

-40°C to +85°C

+ Denotes lead-free package.

PIN-PACKAGE

24 QSOP

24 QSOP

Minimal Operating Circuit

+5V INPUT

MAX1717

BATTERY

2.5V TO 28V

DAC

INPUTS

VCC

VDD

SKP/SDN

V+

FBS

ILIM

BST

DH

GNDS

A/B

REF

TON

LX

CC

DL

D0

GND

D1

D2

FB

D3

TIME

D4

VGATE

OUTPUT

0.925V TO 2V

________________________________________________________________ Maxim Integrated Products 1

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.

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