3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING AND POWER DMOS OUTPUTS

The A8909CLB is a three-phase brushless, back-EMF sensing, spindle-motor driver that integrates analog bipolar, analog and digital CMOS control functions, and DMOS power outputs on a single monolithic chip. It provides complete back-EMF sensing, commutation control, and drive of a spindle motor, and provides for an orderly spin-down in the event of supply-voltage removal. Energy for retracting the heads is regenerated from the spinning motor, while a controlled delay allows for a full retract before dynamic braking. The pulse-width modulation system and power DMOS outputs provide control of high currents with minimum power dissipation in the chip, and minimal average power supply current.

FEATURES
■ 3 Half-Bridge DMOS Outputs with Low ON Resistance
■ 5 V Logic Supply, 5 V or 12 V Motor Supply
■ Back-EMF Sensing and Commutation Algorithm with Digital Programmable Timing Functions
■ Adaptive Adjustable Digital Commutation Delay
■ DC-to-DC Boost Voltage Generator for Source and Sink Gate Drive
■ PWM Current-Control Loop with Sink-Side Chopping
■ Transconductance Error Amp. with External Compensation for Average Supply Current Control Loop
■ PWM Oscillator with External Frequency-Setting Components
■ Current-Sense Amplifier
■ Power-Down Brake with Delay Set by External RC
■ Analog/Digital Multiplexer for Diagnostics and Testing
■ Thermal Monitor Voltage Available on Multiplexer
■ Back-EMF Zero-Crossing Output for Monitoring Motor Speed
■ Sleep Mode
■ Serial Port for Programming Modes, Multiplexer, & Programmable Timers