ML4425

www.fairchildsemi.com ML4425 Sensorless BLDC Motor Controller Features Stand-alone operation Motor starts and stops with power to IC On-board start sequence: Align ♦ Ramp ♦ Set Speed Patented Back-EMF commutation technique provides jitterless torque for minimum “spin-up” time Onboard speed control loop PLL used for commutation provides noise immunity from PWM spikes, compared to noise sensitive zero crossing technique PWM control for maximum efficiency Direct FET drive for 12V motors; drives high voltage motors with IC buffers General Description The ML4425 PWM motor controller provides all of the functions necessary for starting and controlling the speed of delta or wye wound Brushless DC (BLDC) motors without Hall Effect sensors. Back EMF voltage is sensed from the motor windings to determine the proper commutation phase sequence using a PLL. This patented sensing technique will commutate a wide range of 3-Phase BLDC motors and is insensitive to PWM noise and motor snubbing circuitry. The ML4425 limits the motor current using a constant offtime PWM control loop. The velocity loop is controlled with an onboard amplifier. The ML4425 has circuitry to ensure that there is no shoot-through in directly driven external power MOSFETs. The timing of the start-up sequence is determined by the selection of three timing capacitors. This allows optimization for a wide range of motors and loads. Block Diagram 17 VDD 750nA FB A 22 FB B 23 FB C 24 BACK EMF SAMPLER 500nA V...