8909

8909 ADVANCE INFORMATION DATA SHEET 3-PHASE BRUSHLESS DC MOTOR (Subject to change without notice) CONTROLLER/DRIVER WITH BACK-EMF SENSING April 3, 1995 AND POWER DMOS OUTPUTS 8909 Data Sheet 26301.10 3-PHASE BRUSHLESS DC MOTOR CONTROLLER/DRIVER WITH BACK-EMF SENSING AND POWER DMOS OUTPUTS SUPPLY OSC C OSC R LDC V BH V BL GND GND CLOCK LOAD SCLK 1 2 3 4 5 6 7 8 9 10 VDD 28 27 26 25 24 23 22 21 20 19 18 17 16 15 VM C TAP OUTC BRAKE FCOM OUTB GND GND R SENSE BKDELAY ERRCAP OUTA 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 spindown 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 currrent. The internal sensorless commutation algorithm is based on earlier Allegro back-EMF sensing spindle-motor driver products that have proven capability. This system features digital adaptive commutation delay, programmable digital commutation timers, and minimal micro overhead during startup. This results in enhanced r...