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MAX31740
Ultra-Simple Fan-Speed Controller
General Description
Features
The MAX31740 is a sophisticated, yet easy-to-use fan-
speed controller. It monitors the temperature of an external
NTC thermistor and generates a PWM signal that can be
used to control the speed of a 2, 3, or 4-wire fan. The fan
control characteristics are set using external resistors,
thereby eliminating the need for an external microcon-
troller. Controllable characteristics include the starting
temperature for fan control, PWM frequency, fan speed
at low temperatures, and slope of the temperature-duty-
cycle transfer function.
●ꢀ Self-ContainedꢀPWMꢀFanꢀControl—NoꢀMicroꢀNeeded
●ꢀ ControlsꢀSpeedꢀofꢀ2-,ꢀ3-,ꢀorꢀ4-WireꢀFans
●ꢀ ResistorsꢀSetꢀFanꢀControlꢀCharacteristics
●ꢀ Smooth,ꢀLinearlyꢀVaryingꢀPWMꢀDutyꢀCycleꢀMinimizesꢀ
Audibility of Fan Noise
●ꢀ AccuratelyꢀMonitorsꢀExternalꢀThermistorꢀTemperature
●ꢀ 3.0Vꢀtoꢀ5.5VꢀOperatingꢀVoltageꢀRange
●ꢀ -40°Cꢀtoꢀ+125°CꢀOperatingꢀTemperatureꢀRange
●ꢀ AEC-Q100ꢀqualifiedꢀMAX31740ATA/VY+
Because the operating characteristics are selected by
hardwired passive components, a simple, low-cost fan-
speed controller can be implemented without the need
for firmware development. This can dramatically reduce
development time for the fan control function.
Applications
●ꢀ ConsumerꢀEquipment
●ꢀ CommunicationsꢀEquipment
●ꢀ ComputingꢀEquipment
●ꢀ IndustrialꢀEquipment
The MAX31740 is available in a 2mm x 3mm, 8-pin TDFN
package.
Ordering Information appears at end of data sheet.
Typical Application Circuits
2-WIRE FAN-SPEED CONTROLLER
4-WIRE FAN-SPEED CONTROLLER
V
V
V
V
DD
DD
R
ST
C
B
R
ST
C
B
B
B
DD
DD
R
R
VFAN
SENSE
D0
SENSE
D0
R
R
R
R
D1
D1
FREQ
FREQ
C
C
F
F
VFAN
MAX31740
MAX31740
DMIN
DMIN
TACH OR
LOCKED
ROTOR
PWM_OUT
N
PWM_OUT
33Hz
25kHz
D2
D2
GND SLOPE
R
GND SLOPE
R
SLOPE
SLOPE
19-6697; Rev 3; 12/20