
8902–A
3-PHASE BRUSHLESS DC
MOTOR CONTROLLER/DRIVER
TERMINAL FUNCTIONS
Term.
Terminal Name
Function
1
LOAD SUPPLY
V
BB
; the 5 V or 12 V motor supply.
2
C
D2
One of two capacitors used to generate the ideal commutation points from the
back-EMF zero crossing points.
3
C
WD
Timing capacitor used by the watchdog circuit to disable the back-EMF compara-
tors during commutation transients, and to detect incorrect motor position.
4
C
ST
Startup oscillator timing capacitor.
5
OUT
A
Power amplifier A output to motor.
6-7
GROUND
Power and logic ground and thermal heat sink.
8
OUT
B
Power amplifier B output to motor.
9
OUT
C
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.
External capacitor and resistor at B
RAKE
provide brake delay. The brake function
can also be controlled via the serial port.
12
C
RES
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
V
DD
; the 5 V 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
C
D1
One of two capacitors used to generate the ideal commutation points from the
back-EMF zero crossing points.