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[6/24/2012 10:36:10 am] search: contact sales copyright ? 2012 allegro microsystems, inc. sitemap | privacy policy | contact webmaster contact sales | home | quality & environment | request samples | careers | legal 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. datasheets contact your local sales rep sample & buy contact your local sales rep receive product alerts we'll notify you when there are updates to this product. sign up 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 audible noise part number specifications and availability part number package type temperature rohs compliant part composition / rohs data comments samples check distributor stock A4942GESTR-T 20-lead qfn -40 c to 105 c yes view data new contact your local sales rep check distributor stock 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. product image 1 2 click the image to view larger
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