ML4411

May 1997 ML4411*/ML4411A** Sensorless Spindle Motor Controller GENERAL DESCRIPTION The ML4411 provides complete commutation for delta or wye wound Brushless DC (BLDC) motors without the need for signals from Hall Effect Sensors. This IC senses the back EMF of the three motor windings (no neutral required) to determine the proper commutation phase angle using Phase Lock Loop techniques. This technique will commutate virtually any 3-phase BLDC motor and is insensitive to PWM noise and motor snubbing. The ML4411 is architecturally similar to the ML4410 but with improved braking and brown-out recovery circuitry. Included in the ML4411 is the circuitry necessary for a Hard Disk Drive microcontroller driven control loop. The ML4411 controls motor current with either a constant off-time PWM or linear current control driven by the microcontroller. Braking and Power Fail are also included in the ML4411. The timing of the start-up sequencing is determined by the micro, allowing the system to be optimized for a wide range of motors and inertial loads. The ML4411 modulates the gates of external N-Channel power MOSFETs to regulate the motor current. The IC drives P-Channel MOSFETs directly. The ML4411A includes a comparator on the P3 output to prevent cross-conduction. FEATURES s s s s s s s Back-EMF commutation provides maximum torque for minimum “spin-up” time for spindle motors Accurate, jitter-free phase locked motor speed feedback output Linear or PWM motor current control Easy mic...