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 control
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 factory
programmed and is not pin selectable.
All versions include an overtemperature output (active-low OT).
Active-low 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 active-low FANFAIL output that indicates a failed fan. See the Selector Guide in the full data sheet 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.
Key Features
Applications/Uses
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
Notes: **This pricing is BUDGETARY, for comparing similar parts. Prices are in
U.S. dollars and subject to change. Quantity pricing may vary
substantially and international prices may differ due to local
duties, taxes, fees, and exchange rates. For volume-specific prices
and delivery, please see the price and availability page
or contact an authorized distributor.
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