Full-bridge motordriver med PWM strømreference

The A3918 from Allegro MicroSystems Europe is a new full-bridge DC motor driver IC capable of a continuous output current of 1 A and operating voltages from 2.5 to 9 V. An internal PWM current reference allows the user to select the peak chop current using only a resistor.

The new device is the latest addition to Allegro’s low-voltage family of motor drivers, providing a single full-bridge option to complement the dual full-bridge capability found in the company’s existing family of devices. The single supply and simple logic interface makes this an ideal product for applications involving single-cell lithium-ion batteries.

The A3918 has a unique design which incorporates a two-stage charge pump that ensures that the driver has a low output resistance over the entire supply range from 9 V down to 2.5 V. This feature dramatically improves battery life when battery voltages are low because the switches do not become highly resistive due to reduced gate drive. The result is more energy for the load and lower heating and power dissipation in the bridge.

For overcurrent or locked-rotor conditions, an internal fixed off-time PWM timer sets a peak current with the addition of a current sense resistor. An overcurrent output flag is provided that notifies the user when the current in the motor winding reaches the peak current.

The A3918 is targeted at low-voltage battery-operated motor control applications in the consumer, industrial and medical markets. Typical applications include point-of-sale devices, gaming controllers, USB powered devices, digital still cameras, robotics, valve control and infusion pumps.

The A3918SESTR-T is provided in a 16-pin, 3 mm × 3 mm, 0.75 mm nominal overall height QFN package, with exposed pad for enhanced thermal dissipation. It is lead (Pb) free, with 100% matt tin leadframe plating.