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FDD412A/B
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
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