8902–A

3-PHASE BRUSHLESS DC

MOTOR CONTROLLER/DRIVER

TERMINAL FUNCTIONS

Term.

Terminal Name

Function

1

LOAD SUPPLY

One of two capacitors used to generate the ideal commutation points from the

back-EMF zero crossing points.

Timing capacitor used by the watchdog circuit to disable the back-EMF compara-

tors during commutation transients, and to detect incorrect motor position.

Startup oscillator timing capacitor.

5

Power amplifier A output to motor.

6-7

GROUND

Power and logic ground and thermal heat sink.

8

Power amplifier B output to motor.

9

Power amplifier C output to motor.

10

CENTERTAP

Motor centertap connection for back-EMF detection circuitry.

11

BRAKE

Active low turns ON all three sink drivers shorting the motor windings to ground.

can also be controlled via the serial port.

12

External reservoir capacitor used to hold charge to drive the source drivers’

gates. Also provides power for brake circuit.

13

FILTER

Analog voltage input to control motor current. Also, compensation node for

internal speed control loop.

14

SECTOR DATA

External tachometer input. Can use sector or index pulses from disk to provide

precise motor speed feedback to internal frequency-locked loop.

15

LOGIC SUPPLY

16

OSCILLATOR

Clock input for the speed reference counter. Typical max. frequency is 10 MHz.

17

DATA OUT

Thermal shutdown indicator, FCOM, TACH, or SYNC signals available in real

time, controlled by 2-bit multiplexer in serial port.

18-19

GROUND

Power and logic ground and thermal heat sink.

20

RESET

When pulled low forces the chip into sleep mode; clears all serial port bits.

21

CHIP SELECT

Strobe input (active low) for data word.

22

CLOCK

Clock input for serial port.

23

DATA IN

Sequential data input for the serial port.

24

One of two capacitors used to generate the ideal commutation points from the

back-EMF zero crossing points.