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Spindle Motor - Fujitsu M255XK Customer Engineering Manual

5 1/4" mini-flexible disk drive
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DlRECIlON SELECI
input signal
----------~------~
Step
in
~--------~:~~----
STEP input signal
Step
out
Direction latch output-
,...---...,';i-------
; approx.3
Omsec.
Over-drive circuit input
~--~---~---+------~--~--4-----1~
Motor driver input
PHASE A
PHASE 8
PHASE
I
PHASE!" _ _
~
"
Figl.lre 3-7 Typical Stepping Motor Control Circuit Waveforms
3.2.3 Spindle Motor
The Spindle Motor is started and stopped by the "Motor On" interface signal.
The spindle motor is an AC, long
Ii
fe, brushless 3-phase motor driven with a
special 3-phase driver IC.
The flow of current, and the switching of direction of
excitation, is performed by signals from the Hall element mounted on the circuit
card on the outer periphery of the motor's rotor, with the sequential drive coil and
direction of excitation controlled so they switch to the prescribed direction of
rotation.
Rotational speed is accurately maintained, at the desired value, by frequency to
voltage conversion of a feedback signal received from an AC tachometer etched
on the circuit card inside the motor's rotor. Another servo IC is used to apply this
feedback to the voltage control section of the 3-phase driver IC.
3-10
TS-021-013087 ••• 01

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