M56785FP 데이터 시트보기 (PDF) - MITSUBISHI ELECTRIC

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M56785FP

SPINDLE MOTOR DRIVER

MITSUBISHI ELECTRIC  

MITSUBISHI <CONTROL / DRIVER IC>

M56785FP

SPINDLE MOTOR DRIVER

AUTOMATICALY STOP AFTER REVERSE

BRAKING 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

COMMUTATED SHORT

BRAKING

ALL SHORT

BRAKING

HIGH

REVERSE BRAKING

OUTPUT OPEN

[only inertia]

Figure 7.

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