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General Description

The MAX6643/MAX6644/MAX6645 monitor temperature

and automatically adjust fan speed to ensure optimum

cooling while minimizing acoustic noise from the fan.

Each device measures two temperature locations.

The MAX6643/MAX6644/MAX6645 generate a PWM

waveform that drives an external power transistor, which

in turn modulates the fan’s power supply. The

MAX6643/MAX6644/MAX6645 monitor temperature and

adjust the duty cycle of the PWM output waveform to con-

trol the fan’s speed according to the cooling needs of the

system. The MAX6643 monitors its own die temperature

and an optional external transistor’s temperature, while the

MAX6644 and MAX6645 each monitor the temperatures

of one or two external diode-connected transistors.

The MAX6643/MAX6644/MAX6645 are available in H

and L versions. The H versions are trimmed for higher

temperature trip thresholds than the L versions. The

MAX6643 and MAX6644 have nine selectable trip tem-

peratures (in 5°C increments). The MAX6645 is factory

programmed and is not pin selectable.

All versions include an overtemperature output (OT).

OT can be used for warning or system shutdown. The

MAX6643 also features a FULLSPD input that forces the

PWM duty cycle to 100%. The MAX6643/MAX6644/

MAX6645 also feature a FANFAIL output that indicates

a failed fan. See the Selector Guide for a complete list

of each device’s functions.

The MAX6643 and MAX6644 are available in a small

16-pin QSOP package and the MAX6645 is available in

a 10-pin µMAX

package. All versions operate from

3.0V to 5.5V supply voltages and consume 500µA (typ)

supply current.

Applications

Networking Equipment

Storage Equipment

Servers

Desktop Computers

Workstations

Features

♦ Simple, Automatic Fan-Speed Control

♦ Internal and External Temperature Sensing

♦ Detect Fan Failure Through Locked-Rotor Output,

Tachometer Output, or Fan-Supply Current

Sensing

♦ Multiple, 1.6% Output Duty-Cycle Steps for Low

Audibility of Fan-Speed Changes

♦ Pin-Selectable or Factory-Selectable Low-

Temperature Fan Threshold

♦ Pin-Selectable or Factory-Selectable High-

Temperature Fan Threshold

♦ Spin-Up Time Ensures Fan Start

♦ Fan-Start Delay Minimizes Power-Supply Load at

Power-Up

♦ 32Hz PWM Output

♦ Controlled Duty-Cycle Rate-of-Change Ensures

Good Acoustic Performance

♦ 2°C Temperature-Measurement Accuracy

♦ FULLSPD/FULLSPD Input Sets PWM to 100%

♦ Pin-Selectable OT Output Threshold

♦ 16-Pin QSOP and 10-Pin µMAX Packages

MAX6643/MAX6644/MAX6645

Automatic PWM Fan-Speed Controllers with

Overtemperature Output

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3305; Rev 1; 8/04

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.

Pin Configurations, Typical Operating Circuit, and Selector

Guide appear at end of data sheet.

PART TEMP RANGE

PIN-PACKAGE

MAX6643LBFAEE -40°C to +125°C 16 QSOP

MAX6643LAFAEE*

-40°C to +125°C 16 QSOP

MAX6643LBBAEE -40°C to +125°C 16 QSOP

MAX6643LABAEE*

-40°C to +125°C 16 QSOP

MAX6643HAFAEE*

-40°C to +125°C 16 QSOP

MAX6644LBAAEE -40°C to +125°C 16 QSOP

MAX6644HAFAEE*

-40°C to +125°C 16 QSOP

MAX6645ABFAUB*

-40°C to +125°C 10 µMAX

MAX6645BAFAUB -40°C to +125°C 10 µMAX

*Future product—contact factory for availability.

µMAX is a registered trademark of Maxim Integrated Products, Inc.

1 2 3 4 5 6 ... 16 17

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Página 1 - Overtemperature Output

General DescriptionThe MAX6643/MAX6644/MAX6645 monitor temperatureand automatically adjust fan speed to ensure optimumcooling while minimizing acousti

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MAX6643/MAX6644/MAX6645Automatic PWM Fan-Speed Controllers withOvertemperature OutputMaxim cannot assume responsibility for use of any circuitry other

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Detailed DescriptionThe MAX6643/MAX6644/MAX6645 measure temperatureand automatically adjust fan speed to ensure optimumcooling while minimizing acoust

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MAX6643/MAX6644/MAX6645There are two options for the behavior of the PWM out-puts at power-up. Option 1 (minimum duty cycle = 0):at power-up, the PWM

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THIGH, the duty cycle may increase just a few percentabove the minimum duty cycle. If the power dissipationor ambient temperature increases to a high-

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MAX6643/MAX6644/MAX6645systems, or for an over-temperature condition (by con-necting OT to FULLSPD). FULLSPD InputThe MAX6643_B_ features a FULLSPD in

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MAX6643/MAX6644/MAX6645Automatic PWM Fan-Speed Controllers withOvertemperature Output_________________________________________________________________

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