Power Electronics

Full-Bridge PWM Motor Driver with Synchronous Rectification

Allegro announces a new full-bridge motor driver IC that is designed for bidirectional pulse width modulated (PWM) current control of inductive loads and is capable of continuous output currents to ±1.5 A and operating voltages to 50 V. Allegro's A4973 has an internal fixed off-time PWM current-control circuitry that can be used to regulate the maximum load current to a desired value. The peak load current limit is set by the user's selection of an input reference voltage and external sensing resistor. The fixed off-time pulse duration is set by a user-selected external RC timing network. Internal circuit protection includes thermal shutdown with hysteresis, transient suppression diodes, and crossover current protection. Special power-up sequencing is not required.

With the ENABLE input held low, the PHASE input controls load current polarity by selecting the appropriate source and sink driver pair. The MODE input determines whether the PWM current-control circuitry operates in a slow current-decay mode (only the selected source driver switching) or in a fast current-decay mode (selected source and sink switching). A user-selectable blanking window prevents false triggering of the PWM current-control circuitry. With the ENABLE input held high, all output drivers are disabled. A sleep mode is provided to reduce power consumption. When a logic low is applied to the BRAKE input, the braking function is enabled. This overrides ENABLE and PHASE to turn off both source drivers and turn on both sink drivers. The brake function can be used to dynamically brake brush DC motors.

The A4973 is supplied in a choice of two power packages; a 16-pin dual-in-line plastic package with copper heat-sink tabs, and a 16-pin plastic SOIC with copper heat sink tabs. For both package styles, the power tab is at ground potential and needs no electrical isolation. Each package type is available in a lead (Pb) free version (100% matte tin plated leadframe). The A4973SB-T and A4973SLBTR-T are targeted at the office automation and industrial markets and are priced at $1.79 in quantities of 1,000.

Allegro Microsystems
Part Number: A4973

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