General Description

The MAX6650/MAX6651 fan controllers use an

itor the speed of 5VDC/12VDC brushless fans with built-in

tachometers. They automatically force the fan’s tachome-

ter frequency (fan speed) to match a preprogrammed

value in the Fan-Speed Register by using an external

MOSFET or bipolar transistor to linearly regulate the volt-

age across the fan. The MAX6650 regulates the speed of

a single fan by monitoring its tachometer output. The

MAX6651 also regulates the speed of a single fan, but it

contains additional tachometer inputs to monitor up to four

fans and control them as a single unit when they are used

in parallel.

The MAX6650/MAX6651 provide general-purpose

input/output (GPIO) pins that serve as digital inputs,

digital outputs, or various hardware interfaces. Capable

of sinking 10mA, these open-drain inputs/outputs can

drive an LED. To add additional hardware control, con-

figure GPIO1 to fully turn on the fan in case of software

failure. To generate an interrupt when a fault condition

is detected, configure GPIO0 to behave as an active-

low alert output. Synchronize multiple devices by set-

ting GPIO2 (MAX6651 only) as an internal clock output

or an external clock input.

The MAX6650 is available in a space-saving 10-pin

µMAX package, and the MAX6651 is available in a

small 16-pin QSOP package.

________________________Applications

RAID

Desktop Computers

Servers

Networking

Workstations

Telecommunications

____________________________Features

o Closed/Open-Loop Fan-Speed Control for

5V/12V Fans

o Monitors Tachometer Output

Single Tachometer (MAX6650)

Up to Four Tachometers (MAX6651)

o Programmable Alert Output

o GPIOs

o Hardware Full-On Override

o Synchronize Multiple Fans

o Four Selectable Slave Addresses

o 3V to 5.5V Supply Voltage

o Small Packages

10-Pin µMAX (MAX6650)

16-Pin QSOP (MAX6651)

Fan-Speed Regulators and Monitors

________________________________________________________________ Maxim Integrated Products

1

19-1784; Rev 2; 12/01

Ordering Information

10 µMAX

PIN-PACKAGE

TEMP RANGE

-40°C to +85°C

MAX6650EUB

PART

16 QSOP

-40°C to +85°C

MAX6651EEE

SMBus is a trademark of Intel Corp.

MAX6650

SCL

10k

Ω

SDA

GPIO0

OUT

ADD

GND

FB

TACH0

3V TO 5.5V

5V OR 12V

10

µF

INTERFACE

GPIO1

LED

FAN

FULL ON

ALERT

Typical Operating Circuit

Pin Configurations appear 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.