Posted to News on 28th Jul 2008, 17:42
Low-voltage motor driver suits battery-powered equipment
The new A3906 from Allegro Microsystems Europe is a low-voltage dual full-bridge motor driver IC (integrated circuit) designed to drive one bipolar stepper motor or two DC motors. Part of Allegro's low-voltage motor driver series targeted at portable battery-powered applications in the consumer, industrial, office automation and medical markets, the driver has output channels rated at 1A each and an operating supply voltage range of 2.5V. Key features include fixed off-time PWM (pulse-width modulated) current control, low 'on' resistance DMOS outputs and a peak current flag output.
Output current for each full bridge circuit can be controlled using the internal fixed off-time PWM regulator or by PWM control of the two logic inputs. The current flag output, which is used to detect DC motor stall conditions and enables control of the stall time for improved battery life and to prevent damage to the motor, is triggered when the output current reaches the trip level for the internal PWM regulator and stays on for a minimum of 300us.
The output drivers are all N-channel DMOS full bridges. An internal charge pump supply doubles or even triples the back bias voltage to ensure proper gate drive voltage for the high- and low-side DMOS devices. The resulting stable gate drive provides a consistent output 'on' resistance over the full input voltage range.
Protection features include thermal shutdown, undervoltage lockout and crossover current protection. Internal synchronous rectification control circuitry is provided to improve power dissipation during PWM operation.
The A3906 is supplied in a 4 x 4mm, 20-contact QFN package with exposed thermal pad. This small-footprint package is lead-free with 100 per cent matte tin leadframe plating.
