Fujitsu M2361A Customer Engineering Manual page 157

u. Power amplifier interface
This is the interface between the power amplifier for driving the
rotary actuator and spindle motor and the servo circuit.
~en
the
coarse control operation is performed, the interface selects VLERR by
means of *CORSE. When the fine control is performed, the interface
selects POSER by means of *GLNMD. One of these signals is sent to
the power amplifier as the power amplifier drive signal (PADRV).
~en
the rezero operation is performed, the amplifier gain of PADRV is
reduced to prevent excessive acceleration force from being applied to
the carriage and the head. In addition, a DC bias circuit is
provided to prevent the head from moving away from the CSS area when
the spindle motor rotation is lower than the specified rotational
speed (3,600 rpm
-2%).
The interface for the power amplifier of the
rotary actuator includes the Current Sense signal (CSNSE) which is
proportional to the current in the drive coil and the Overcurrent
signal (OVCRT) which indicates excessive current flow. The interface
for the power amplifier of the spindle motor includes the Spindle
Start signal (*SPSTT) which indicates the start/stop of the motor,
the Speed Alarm signal (SPALH) which indicates that the rotational
speed is not in the range of 3,600 rpm +2%, and the Hall alarm signal
(HALM) which indicates an abnormal condition of the hall-effect
element used for monitoring the spindle motor rotation.
v. Power amplifier for rotary actuator
This amplifier provides drive coil current proportional to PADRV sent
through the power amplifier interface and sends CSNSE to the servo
circuit upon detection of coil current. In addition, it sets OVCRT
high to indicate an abnormal condition when current of SA or more
flows for 0.7 seconds or longer.
w. Power amplifier for spindle motor
4 - 86
This amplifier controls the spindle motor so that it rotates at the
specified speed (3,600 rpm) when the Spindle Start signal (*SPSTT) is
"0". The rotational speed is checked by the output of three
hall-effect elements which are contained in the motor. The
rotational speed is compared with the specified speed each time the
disk rotates; if the speed is lower than 3,600 rpm, the amplifier
provides current and, if the speed is higher than 3,600 rpm, current
does not flow, allowing the disks to be rotated by the force of
inertia. The Speed Alarm signal (SPALM) is changed from "1" to "0"
when the rotational speed comes up to 3,600 rpm, and changed to "1"
again when the rotational speed is not within the specified range.
The rotational speed monitor circuit is reset when the disk is
restai-ted.
The following diagram shows the outputs of the hall-effect elements.
B03P-4825-0002A ... OIA