M56784 Mitsubishi, M56784 Datasheet - Page 7

• Manufacturer Part Number: M56784
• Description: SPINDLE MOTOR DRIVER
• Manufacturer: Mitsubishi

AUTOMATICALY STOP AFTER REVERSE BRAK-
ING FUNCTION
Figure 5 also shows the automaticaly stop (after the reverse
braking) circuit. Figure 6 is its function table which shows whether
the automaticaly stop function is on or off, and its state is
determined by MODE3 input.
When the MODE3 is open or high, the motor will stop rotating
automaticaly after the reverse braking.
When the MODE3 is low or connected to GND, the motor will
continue the reverse rotation. This function is useful for the case
that the system doesn’t require the automaticaly stop function, and
in the system a motor receives a stop command from the outside
of this IC. For example, a com can detect the reverse rotation
Figure 6.
REVERSE TORQUE MODE SELECT FUNCTION
In the 4 times speed and the 6 times speed CDROM drive system,
the reverse braking style has been used for a deceleration of the
rotation speed. However, in the CDROM drive system above an 8
times speed, the motor current above 0.5A is needed, because a
high speed access time are required for motor driver ICs. If the
reverse braking is used at 0.5A, the IC junction temperature will be
too much high, and the heat loss of the IC will be large.
Therefore, this motor driver has the braking mode select function
(REVERSE BRAKING MODE and SHORT BRAKING MODE). The
breaking mode can be determined by the external logic signals
synchronizing with servo timing, and it can make a heat loss of the
IC smaller by adjusting the junction temperature.
Figure 7 shows the reverse torque mode select function table. If
you want the former braking style (the reverse braking), please
select only the REVERSE BRAKING mode [MODE1 = LOW or
OPEN and MODE2 = HIGH]. But the heat loss will be larger, and
Figure 7.
MODE2
OPEN or HIGH
AUTOMATIC
STOP
BRAKING MODE (ECR < EC) SELECT FUNCTION TABLE
LOW
or
OPEN
HIGH
MODE3
COMMUTATED SHORT
BRAKING
REVERSE BRAKING
UN-AUTOMATIC
(NON-STOP)
LOW or OPEN
GND
MODE1
SHORT BRAKING (2)
OUTPUT OPEN
[only inertia]
ALL SHORT
BRAKING
HIGH
from the RDS pin output, and can control all the torque of a motor.
So it can stop the motor outside this IC.
FG FUNCTION
Figure 5 also shows the circuits and the functions of the frequency
generator. The FG pin outputs the square pulse signal
synchronizing with the hall inputs [Hv+ and Hv-] timming.
The FG pin is pulled-up to V
10Kohm].
sometimes external heat sink would be necessary.
If it is possible to get ports more than two from com, you can
flexibly control the four kinds of BRAKING MODE. So the heat loss
can be half as usual. For example, the REVERSE BRAKING
MODE is on under the CLV control, and the ALL SHORT
BRAKING MODE is for seeking. When the motor should be
stopped, the ALL SHORT BRAKING MODE or the REVERSE
BRAKING MODE is available.
If you can only get one port, you can control only the MODE2. At
this time, you can control the two kinds of BRAKING MODE
[commutated short or reverse] on condition that the MODE1 is set
to be LOW or OPEN.
MITSUBISHI <CONTROL / DRIVER IC>
SPINDLE MOTOR DRIVER
CC
1 by an internal resistor [typ.
M56784FP