Rainbow Electronics MAX6645 - Manual

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
MAX6643 LBFAEE -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
MAX6644 LBAAEE -40 °C to +125°C 16 QSOP
MAX6644HAFAEE* -40 °C to +125°C 16 QSOP
MAX6645 ABFAUB* -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.