ML4428

April 1997 PRELIMINARY ML4428* Sensorless Smart-Start™ BLDC PWM Motor Controller GENERAL DESCRIPTION The ML4428 motor controller provides all of the functions necessary for starting and controlling the speed of delta or wye-wound Brushless DC (BLDC) Motors without the need for Hall Effect sensors. Back-EMF voltage is sensed from the motor windings to determine the proper commutation phase sequence using PLL techniques. The patented back-EMF sensing technique used will commutate virtually any 3-phase BLDC motor that has at least a 30% variation in inductance during rotation and is insensitive to PWM noise and motor snubbing circuitry. The ML4428 also utilizes a patented start-up technique which samples the rotor position and applies the proper drive to accelerate the motor. This ensures no reverse rotation at start-up and reduces total start-up time. FEATURES s s Stand-alone operation with forward and reverse On-board start sequence: Sense Position Æ Drive Æ Accelerate Æ Set Speed No backward movement at start-up Patented back-EMF commutation technique Simple variable speed control with on-board reference Single external resistor sets all critical currents PWM control for maximum efficiency or linear control for minimum noise 12V operation provides direct FET drive for 12V motors Drives high voltage motors with high side FET drivers s s s s s s s s Guaranteed no shoot-through when driving external FET gates directly * Some Packages Are End Of Life BLOCK DIAGRAM/TYPICAL ...