Dwg. PP-040B

ABSOLUTE MAXIMUM RATINGS

Logic Input Voltage Range,

See Graph

Operating Temperature Range,

Storage Temperature Range,

-55

† Fault conditions that produce excessive junction

temperature will activate device thermal shutdown

circuitry. These conditions can be tolerated, but

should be avoided.

Output current rating may be restricted to a value

determined by system concerns and factors.

These include: system duty cycle and timing,

ambient temperature, and use of any heatsinking

and/or forced cooling. For reliable operation, the

specified maximum junction temperature should

not be exceeded.

Always order by complete part number, e.g., A8902CLBA .

The A8902CLBA is a three-phase brushless dc motor controller/

driver for use in 5 V or 12 V hard-disk drives. The three half-bridge

outputs are low on-resistance n-channel DMOS devices capable of

driving up to 1.25 A. The A8902CLBA provides complete, reliable,

self-contained back-EMF sensing motor startup and running algorithms.

A programmable digital frequency-locked loop speed control circuit

together with the linear current control circuitry provides precise motor

speed regulation.

A serial port allows the user to program various features and

modes of operation, such as the speed control parameters, startup

current limit, sleep mode, diagnostic modes, and others.

The A8902CLBA is fabricated in Allegro’s BCD (Bipolar CMOS

DMOS) process, an advanced mixed-signal technology that combines

bipolar, analog and digital CMOS, and DMOS power devices. The

A8902CLBA is provided in a 24-lead wide-body SOIC batwing package.

It provides for the smallest possible construction in surface-mount

applications.

FEATURES

s DMOS Outputs

s Startup Commutation Circuitry

s Back-EMF Commutation Circuitry

s Serial Port Interface

s Frequency-Locked Loop Speed Control

s Sector Data Tachometer Signal Input

s Programmable Start-Up Current

s Diagnostics Mode

s Sleep Mode

s Linear Current Control

s Internal Current Sensing

s Dynamic Braking Through Serial Port

s Power-Down Dynamic Braking

s System Diagnostics Data Out

s Data Out Ported in Real Time

s Internal Thermal Shutdown Circuitry

3-PHASE BRUSHLESS DC MOTOR

CONTROLLER/DRIVER WITH BACK-EMF SENSING

1

2

3

4

5

6

7

8

9

24

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9

BRAKE

FILTER

DATA IN

LOGIC

SUPPLY

GROUND

CHIP SELECT

CLOCK

RESET

GROUND

GROUND

GROUND

DD

V

C

ST

OUTA

OUTB

OUTC

C D1

BB

V

LOAD

SUPPLY

C WD

C D2

DATA OUT

SECTOR

DATA

CENTERTAP

OSCILLATOR

C RES

FLL

MUX

COMMUTATION

DELAY

BOOST

CHARGE

PUMP

8902–A