Allegro MicroSystems introduced two automotive grade (temperature and voltage rated) three phase BLDC motor controller integrated circuits. These control ICs integrate 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 appropriate in a BEMF (sensor-less) design. 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 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 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 used with the IC (such as sensorless BEMF commutation schemes). The A3930 and A3931 are offered in a small thermally efficient 48L eLQFP package. They are both priced at $3.12 in quantities of 1,000.
Allegro Microsystems, Inc.
508-853-5000, www.allegromicro.com