General Description

The MAX6668/MAX6670 remote-junction thermal

switches with an internal power transistor drive a cool-

ing fan rated for supply voltages up to +12V and

250mA. These devices measure the temperature of an

external P-N junction (typically a diode-connected tran-

sistor) and turn on the fan power switch when the

remote temperature rises above a factory-programmed

threshold. Self-contained and requiring no software

development, the MAX6668/MAX6670 are simple

“drop-in” fan-control solutions for a variety of systems.

The MAX6670 features an open-drain WARN output

that goes active when the remote temperature exceeds

the factory-programmed fan activation threshold by

+15°C. The MAX6670 features an open-drain OT output

that goes active when the remote temperature exceeds

the factory-programmed threshold by +30°C. The

MAX6668/MAX6670 provide a fan-control input,

FORCEON, that allows the fan to be driven externally,

regardless of temperature.

Available temperature thresholds range from +40°C to

+75°C in 5°C increments. Hysteresis is preset to 8°C on

the MAX6668 or pin selectable to 4°C, 8°C, or 12°C

using a three-level logic input on the MAX6670.

Temperature threshold accuracy is ±1°C (typ) and

±2.2°C (max) for remote-junction temperatures from

+40°C to +75°C.

The MAX6668/MAX6670 operate from a +3V to +3.6V

power supply, and are specified over the automotive

temperature range (-40°C to +125°C). The MAX6668 is

offered in an 8-pin µMAX package and the MAX6670 is

available in a space-saving 10-pin µMAX package.

Applications

Notebook and Desktop Computers

Network Switches

PC Power Supplies

Laboratory Instruments

Card Racks

Temperature Alarms

Fan Controls

Features

o +12V, 250mA Integrated Fan Driver

o No Calibration Required

o Pin-Selectable 4°C, 8°C, or 12°C Hysteresis

(MAX6670)

o Factory-Programmed Temperature Thresholds

from +40°C to +75°C

o Overtemperature Warning Signals

o 110µA (typ) Supply Current

o Space-Saving 8-Pin and 10-Pin µMAX Packages

Remote Temperature Switches with Integrated

Fan Controller/Driver

________________________________________________________________ Maxim Integrated Products

1

DXP

GND

PGND

HYST

MAX6670

FORCEON

FANOUT

WARN

OT

DXN

2200pF

2N3904

10k

Ω

10k

Ω

250mA

FAN

+3.3V

+12V

Typical Application Circuit

Ordering Information

19-2133; Rev 2; 11/02

Pin Configuration appears at end of data sheet.

Typical Operating Circuit appears at end of data sheet.

Ordering Information continued 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.

PART

TEMP

RANGE

PIN-

PACKAGE

THRESH-

OLD

(

°C)

MAX6668AUA40 -40

°C to +125°C

8 µMAX

40

MAX6668AUA45 -40

°C to +125°C

8 µMAX

45

MAX6668AUA50 -40

°C to +125°C

8 µMAX

50

MAX6668AUA60 -40

°C to +125°C

8 µMAX

60

MAX6668AUA70 -40

°C to +125°C

8 µMAX

70

MAX6668AUA75 -40

°C to +125°C

8 µMAX

75