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Automotive grade BLDC motor controller ICs debut

Posted: 21 Dec 2007     Print Version  Bookmark and Share

Keywords:three-phase BLDC motor controller ICs  MOSFETs  microprocessor 


Allegro has released two new automotive grade (temperature and voltage rated) three-phase BLDC motor controller ICs. 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: 5V supply for Hall sensors (requires external NPN transistor), integrated charge pump, operation over a wide battery voltage range (5.5V to 50V), extensive diagnostics, and low current quiescent current mode.

The A3931 chip 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 utilised with the IC (such as sensorless BEMF commutation schemes).

The A3930 and A3931 are offered in a small thermally efficient 48L eLQFP packages.

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