8909

3-PHASE BRUSHLESS DC MOTOR

CONTROLLER/DRIVER WITH BACK-EMF SENSING

AND POWER DMOS OUTPUTS

DISCONTINUED

PRODUCT

—

FOR

REFERENCE

ONL

Y

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 mono-

lithic 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 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 resynchronization

during a power fault followed by a restart.

A serial peripheral interface provides control of programmable

features and mode switches. An onboard dc-to-dc converter provides

regulated boost voltage for both the high-side and sink-side gate-drive

less of motor supply voltage (5 V or 12 V).

The A8909CLB is supplied in a 28-lead low-profile SOIC batwing

power package for surface-mount applications.

FEATURES

s 3 Half-Bridge DMOS Outputs with Low ON Resistance

s 5 V Logic Supply, 5 V or 12 V Motor Supply

s Back-EMF Sensing and Commutation Algorithm with

Digital Programmable Timing Functions

s Adaptive Adjustable Digital Commutation Delay

s DC-to-DC Boost Voltage Generator for Source and Sink Gate Drive

s PWM Current-Control Loop with Sink-Side Chopping

s Transconductance Error Amp. with External Compensation for

Average Supply Current Control Loop

s PWM Oscillator with External Frequency-Setting Components

s Current-Sense Amplifier

s Power-Down Brake with Delay Set by External RC

s Analog/Digital Multiplexer for Diagnostics and Testing

s Thermal Monitor Voltage Available on Multiplexer

1

2

3

4

5

9

10

11

12

13

14

15

16

17

18

19

20

23

24

25

26

27

28

VM

SUPPLY

VM

VICMD

OUT

ERRCAP

LDC

GND

GND

AMUX

LOAD

CLOCK

V

BH

C TAP

OUT

BRAKE

FCOM

GND

V

DD

BKDELAY

SCLK

DATA

EXCOMM

7

22

21

8

6

A

C

GND

Dwg. PP-063

TM

MicroSystems, Inc.

TM

A

A

ADVANCE INFORMATION DATA SHEET

(Subject to change without notice)

April 3, 1995

8909