8902–A

3-PHASE BRUSHLESS DC

MOTOR CONTROLLER/DRIVER

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

Dwg. EP-036C

SECTOR

DATA

CHIP SELECT

+5 V

VRET

C

WD

C D2

CD1

RESET

CLOCK

DATA IN

V

BB

C

ST

RES

C

CF2

R F1

CF1

BYPASS

0.22

µF

BYPASS

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

DD

V

BB

V

FLL

MUX

COMMUTATION

DELAY

BOOST

CHARGE

PUMP

OSC (REF)

DATA OUT

FAULT

RB

CB

TYPICAL APPLICATION

BRAKE

FAULT

VBRK

V

– V

FAULT

D

BRAKE

ACTIVATED

Dwg. OP-004

R

B

CB

t

BRK

Braking. A dynamic braking feature of the A8902CLBA shorts the

three motor windings to ground. This is accomplished by turning the

three source drivers OFF and the three sink drivers ON. Activation of

the brake can be implemented through the BRAKE input or through

the D2 bit in the serial port. The supply voltage for the brake circuitry

power failure. Power-down braking with delay can be implemented by

using an external RC and other components to control the brake

terminal, as shown. Brake delay can be set using the equation below

to ensure that voice-coil head retract occurs before the spindle motor

brake is activated. Once the brake is acti-

vated, due to the inherent capacitive input,

the three sink drivers will remain active until

the device is reset.

Centertap. The A8902CLBA internally

simulates the centertap voltage of the motor.

To obtain reliable start-up performance from

motor to motor, the motor centertap should be

connected to this terminal.

External Component Selection. Appli-

cations information regarding the selection of

external component values is available from

the factory for external component selection,

frequency-locked loop speed control, and

commutation delay capacitor selection.