Allegro MicroSytems, Inc. introduces a new low voltage dual full bridge motor driver designed to drive one bipolar stepper motor or two DC motors. This new device is part of Allegro’s low voltage motor driver series targeted at portable battery- powered applications. Each output channel in this new device is rated at 1 A with an operating supply voltage range of 2.5 V to 9 V. Key features include fixed off time PWM current control, low on resistance DMOS outputs and a peak current flag output.
The output current for each full bridge can be controlled using the internal fixed off time PWM regulator or by PWM control of the two logic inputs. The current flag output is triggered when the output current reaches the trip level for the internal PWM regulator and stays on for a minimum of 300 usec. This feature is used to detect DC motor stall conditions and allows for control of the stall time for improved battery life and to prevent damage to the motor.

The output drivers are all N-channel DMOS full bridges. An internal charge pump supply will double or even triple VBB to insure proper gate drive voltage for the high and low side DMOS. The stable gate drive results in a consistent output on resistance over the full input voltage range. Protection features include thermal shutdown, under voltage lockout and crossover current protection. Internal synchronous rectification control circuitry is provided to improve power dissipation during PWM operation.

Allegro’s A3906 is targeted at the consumer, industrial, office automation and medical markets and is supplied in a 4 mm x 4 mm, 20-contact QFN package with exposed thermal pad. This small footprint package is lead (Pb) free with 100% matte tin leadframe plating. It is priced at $0.74 in quantities of 1,000 and has a 14-week lead-time to market.
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