TA8483CP

2006-3-2

15

• Changing and stopping revolutions

• About stepping−out

Monitor the TB6520P/PG's speed detection signal (FG output) to see if a FG signal of the designated frequency

is returned. If not, the motor has stepped out of synchronization, so restart it.

• About overcurrent limiting operation

The TA8483CP's overcurrent detection function works in such a way that the motor current is detected using an

signal is driven high. The TB6520P/PG limits the on

−time of the PWM signal (output by the TB6520P/PG) at a

rising edge of the ISD signal. The on

−time of the upper−side power transistor in the TA8483CP is thereby

limited.

• Lead angle control

The TB6520P/PG determines the commutation timing based on the changeover point (zero

−cross point) of the

induced voltage and reference voltage Vn ( = VM (motor's power supply voltage) divided by2).

During forced starting commutation, the motor operates with a lead angle of 0 degrees. After the motor switches

over to normal

−speed operation, the lead angle is automatically changes to 15 degrees.

(Lead angle of 0 degrees: For 120

−degree switch−on, current starts conducting 30 degrees behind the zero−cross

point. Lead angle of 15 degrees: Current starts conducting 15 degrees behind the zero

−cross point.)

Note that depending on motor characteristics, the waveform of the induced voltage may be distorted, causing

the zero

−cross point to slip out of place. The commutation timing also is thereby made to drift.