MAX6643 Datasheet, PDF (1/17 Pages) Maxim Integrated Products – Automatic PWM Fan-Speed Controllers with Overtemperature Output

19-3305; Rev 2; 3/07
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Automatic PWM Fan-Speed Controllers with
Overtemperature Output
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 and MAX6644 have nine selectable trip
temperatures (in 5°C increments). The MAX6645 is fac-
tory 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
Ordering Information
PART
MAX6643LBFAEE
MAX6643LBBAEE
MAX6644LBAAEE
MAX6645ABFAUB
TEMP RANGE
PIN-
PACKAGE
PKG
CODE
-40°C to +125°C 16 QSOP
-40°C to +125°C 16 QSOP
E16-1
E16-1
-40°C to +125°C 16 QSOP
-40°C to +125°C 10 µMAX
E16-1
U10-2
Pin Configurations, Typical Operating Circuit, and Selector
Guide appear at end of data sheet.
µMAX is a registered trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.