Date: 22/01/2009

Brushless DC motor driver IC with single control pin for vibration motor in phones

Allegro Microsystems has released a new full-bridge motor driver to drive low-voltage, brushless DC motor. Allegro’s A1448 is designed to allow the user to control several functions with a single input control pin. The pin allows for direct input PWM for speed control, is used to initiate the active braking function to reduce motor stop time, and acts as an enable pin to engage micro-power sleep mode to reduce average power consumption when not in use. This new device is targeted at the communications and office automation markets. It is designed for use in vibration motor applications in portable devices that require fast stop start cycles, such as haptic applications and vibration ring tones.

The integrated Hall sensor used to detect the rotational position of an alternating-pole ring magnet achieves motor commutation. A high density CMOS semiconductor process allows the integration of all the necessary electronics. This includes the Hall sensor, the motor control circuitry, and the full output bridge. Low-voltage design techniques have been employed to achieve full device functionality down to 1.8 V VDD.

A1448 provide reverse battery protection and output short circuit protection. The A1448 also employs a soft-switching algorithm to reduce audible switching noise and EMI interference, making this device in BLDC motors superior to existing brush motor solutions.

A micro power sleep mode can be initiated on the CONTROL pin to reduce current consumption for battery management in portable electronic devices. This feature allows for the removal of a FET transistor for switching the device on and off.

Allegro’s DFN (EW) package is the thinnest in the industry with a 0.4 mm maximum thickness that allows for very thin BLDC coin motor designs. The small package outline and low profile make this device ideally suited for use in applications where printed circuit board area and component headroom are at a premium. The A1448 is available in a lead (Pb) free, 6-pin DFN micro-leadframe package, with an exposed pad for enhanced thermal dissipation.