Three Phase Brushless DC Motor PreDriver IC?

Allegro MicroSystems Inc.'s complete three phase brushless DCmotor pre-driver has outputs for direct high current gate drive of an allN-channel power MOSFET. The three phase bridge has a maximum supply voltage of38 V. The A4938 includes Hall element inputs, a sequencerfor commutation control, fixed off time pulse width modulation (PWM) currentcontrol and locked rotor protection. Output current is scalable with the choiceof external MOSFETS. ENABLE, DIRECTION and BRAKE inputs can be used to controlthe motor, speed, position and torque. Output speed can be regulated using opendrain FG1 output that changes state at each Hall transition.

Theexternal MOSFETS can be PWM'd with the ENABLE input or with the internal PWMcurrent regulator. In both cases the A4938 synchronous rectification featurewill turn on the appropriate MOSFET(s) during current decay to reduce powerdissipation. The A4938 uses low cost Hall elements with noise filtering toprevent false commutation signals. A 5V regulated supply output is provided topower the three HALL elements. Internal circuit protection includes thermalshutdown with hysteresis, under voltage lockout, over voltage protection withtwo voltage settings, locked rotor and dead time protection. Special power upsequencing is not required. Operating temperature range is -40 to 85C. The A4938EETTR-T is supplied in a 5 x5 mm 28-lead QFN package with exposed thermal pad.