HALL
---
SPINDLE MOTOR
SENSOR
CONTROL
LSI (IC6A)
MOTOR SPEED
~
MOTOR
~
SPINDLE
INTEGRATOR
DRIVERS
MOTOR
CURRENT LIMITER
DYNAMIC BRAKE
MOTOR
~
VOLTAGE
8.0
MOTORSPEED
CONTROL
FIGURE 27:
Motor
Speed
Control:
PC
Board
20292-XXX
MOTOR SPEED CONTROL:
PC
BOARD 20292-XXX
HALL EFFECT TRANSDUCER
8.1
8.1.1
Located inside the spindle motor hub, this magnetic transducer senses spindle
position and provides dynamic feedback proportional
ta
the speed
of
the mo-
tore
Two
complete square
waves
are generated each motor revolution. The posi-
tional information
is
supplied
ta
the spindle motor
L81
le 6A (pin
3).
Ta
prevent
bath
phases
of
the motor from being selected simultaneously, the motor con-
trol
L81
inverts Hall input
ta
coil A.
SPINDLE MOTOR CONTROL LSI
8.1.2
FIGURE 28:
Motor
Speed
Control
PC
Board
20249-XXX
When power
is
applied
ta
the drive the motor control
L81
pauses until
10
Volts
is
reached before applying current
ta
the motor drive transistors. Lf
10
Volts
is
not achieved within approximately 1 second the motor control
L81
will time-
out and will not apply power
ta
the motor drive transistors.
When current
is
applied, the spindle motor control
L81
sets the motor speed
to 3,600 RPM nominal. The motor speed
is
crystal controlled (YI) with a fre-
quency lock circuit. There
is
no adjustment required for motor speed. The
L81
integrates and transforms the error messages from the Hall effect transducer.
Using this information, it outputs the correct current flow each revolution and
corrects the motor phase driver at output pins 6 and
7.
When power
is
interrupted, the motor control
L81
shorts
bath
phases
of
the
motor
ta
ground allowing the motor-generated back-EMF
ta
brake the spindle
motor.
MeTeR
SPEED CONTROL
PC
BOARD: 20249-XXX 8.2
HALL
..---.
SPEED
~
PULSE
~
INTEGRATOR
~~
DYNAMIC
SENSOR
REFERENCE
SHAPER
BRAKE
+
CURRENT
~
MOTOR
1
L1MIT
DRIVERS
~
·MPU
~
SPINDLE
MOTOR
ST212
PRODUCT
MANUAL/Rev.
B
31
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