Allegro MicroSystems - A4942 Three-Phase Sensorless Fan Driver
http://www.allegromicro.com/en/Products/Motor-Driver-And-Interface-ICs/Brushless-DC-Motor-Drivers/A4942.aspx[7/6/2012 2:19:27 PM]
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Home » Products » Motor Driver and Interface ICs » Brushless DC Motor Drivers » A4942
A4942: Three-Phase Sensorless Fan Driver
The A4942 three phase motor driver incorporates BEMF sensing to eliminate the requirement for Hall sensors
in fan applications.
A closed loop speed control system is integrated into the IC. This allows accurate setting of maximum and
minimum speeds via selection of external resistors. The speed is controlled by duty cycle demand applied to
the PWM input.
The PWM input is allowed to operate over a wide frequency range.
Current limiting is integrated to allow saving the cost and PCB space of an external sense resistor. The current
limit function includes an adjustable soft start to minimize load on the power supply while the fan is ramping up
to speed.
The A4942 is supplied in a 20-contact 4
mm
× 4
mm
QFN package (suffix ES) with exposed pad for enhanced
thermal dissipation. The package is lead (Pb) free, with 100% matte tin leadframe plating.
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Sensorless (no Hall sensors required)
Closed loop speed control
Minimal external components
PWM speed input
FG speed output
Lock detection
Soft start
Overcurrent protection
Soft switching for reduced aud ble noise
Part Number Specifications and Availability
Part Number Package Type Temperature
RoHS
Compliant
Part Composition /
RoHS Data
Comments Samples
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Distributor Stock
A4942GESTR-T 20-lead QFN -40 ° C to 105 ° C Yes View Data New
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local sales rep
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Allegro's products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
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