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Allegro MicroSystems, Inc. Announces New Three-Phase BLDC
MOSFET Pre-Driver Controller ICs
Automotive Grade MOSFET Controllers with On-Board Commutation Logic 
Worcester, MA – December 19, 2007 — Allegro® introduces two new automotive grade (temperature and voltage rated) three phase BLDC motor controller integrated circuits. These control ICs greatly simplify the system design and lower system cost by integrating the commutation logic on-board, which lessons the burden on the system microprocessor. If desired, the Hall sensor inputs can be driven directly by a microprocessor, which makes the A3930 and A3931 key components in a robust BEMF (sensor-less) solution. These controllers are primarily targeted at automotive Hall commutated three-phase motors driven by discrete / external N-Channel MOSFETs.
An on-chip commutation decoder and state machine reads the inputs of three Hall sensor inputs (or IO outputs from a microprocessor). The IC then outputs the correct gate drive signals that control six (three high-side, three low-side) external NMOS MOSFETs, which drive the three-phase BLDC motor. Other key features incorporated on the IC are: 5 V supply for Hall sensor ICs (requires external NPN transistor), integrated charge pump, operation over a wide battery voltage range (5.5 V to 50 V), extensive diagnostics, and low current quiescent current mode.
Allegro’s A3931 is a minor modification of the A3930. In the A3931 an optional pre-positioning function is possible by driving the three Hall inputs low. This provides for a known start-up position for the motor by forcing a position between two detent positions. This start-up condition aids any algorithms that may be utilized with the IC (such as sensorless BEMF commutation schemes).
The A3930 and A3931 are offered in a small thermally efficient 48L eLQFP package.
About Allegro
Allegro MicroSystems, Inc. is a leader in developing, manufacturing and marketing high-performance power and Hall-effect sensor integrated circuits. Allegro's innovative solutions serve high-growth applications within the automotive, communications, computer/office automation, consumer and industrial markets. Allegro is headquartered in Worcester, Massachusetts (USA) with design and applications centers located in North and South America, Asia, and Europe. Further information about Allegro can be found at www.allegromicro.com.
Editorial Contact:
Stephanie Fennelly
Director - Marketing Communications
Tel: (508) 854-5363
sfennelly@allegromicro.com