Sharp FDD-412A - Page 24

FDD412A/B
Read
state
;
Step
motor
STEP-N
STEP DIRECTION-N
Fig. 2.12 Seek Circuit Blodk Diagram
(4) Circuit operation
(a) The STEP signal is used to excite 2 phases at a time in
STEPs 14.
STEP-N )
— fe ee
STEP 1 : ine
STEP
2
ne
|
1 i
egy ns (a memaaert gee
STEP 4 ee
Fig. 2.13 Step Motor Excitation Timing
(b) Upon seek operation, the step motor needs a large current,
but requires a small hold current to flow for displacement
prevention once the seek operation is completed.
In seek operation, the motor is driven at +24V, and at +5V
after completion of the operation. This scheme’*requires less
power consumption. The following points should be noted:
(i) About 60 ms after a head engagement, the motor is driven
at +24V for prevention of dislocation attributable to
the load.
(ii) About 40 ms after the last STEP-N signal, the motor is
driven at +24V for position stabilization (settling).
STEP—N
i}
i
HEAD
'
ENGAGE-N | i |
— +24V ——
Step motor | | :
drive
voltage
———+
5.
Fig. 2.14 Step Motor Drive Voltage Switchover