M56784 데이터 시트보기 (PDF) - MITSUBISHI ELECTRIC

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M56784

SPINDLE MOTOR DRIVER

MITSUBISHI ELECTRIC  

MITSUBISHI <CONTROL / DRIVER IC>

M56784FP

SPINDLE MOTOR DRIVER

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 µcom can detect the reverse rotation

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 VCC1 by an internal resistor [typ.

10Kohm].

MODE3

OPEN or HIGH

GND

AUTOMATIC

STOP

UN-AUTOMATIC

(NON-STOP)

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

sometimes external heat sink would be necessary.

If it is possible to get ports more than two from µcom, 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.

BRAKING MODE (ECR < EC) SELECT FUNCTION TABLE

MODE1

LOW or OPEN

HIGH

MODE2

LOW

or

OPEN

HIGH

COMMUTATED SHORT

BRAKING

REVERSE BRAKING

SHOARLTLBSRHAOKRINTG (2)

BRAKING

OUTPUT OPEN

[only inertia]

Figure 7.

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