TA8483CP

2006-3-2

16

Precautions On Using TB6520P/PG+TA8483CP

• About DC power supply voltage and control voltage on / off sequence

The power

power supply) becomes steadily on.

is sufficiently low (5V or less).

causes a short

−circuit current to flow in due to counterelectromotive force, which could break down the output

transistors.

of the lower

−side output transistors to turn on. Because the motor is turning, a short−circuit current is

generated by counterelectromotive force and flows into the transistors as shown below. This current, if large

enough to exceed the rated current, may break the transistors. (This trouble tends to occur when the motor is

not loaded.)

• About an external oscillator for the TB6520P/PG

The TB6520P/PG has an external oscillator attached as the reference clock source to generate PWM control and

commutation signals. Selection of this oscillator requires caution.

Some oscillator may oscillate erratically if the power supply turn

−on time is fast (1ms or less), causing the

TB6520P/PG to malfunction. In this case, the drive IC, the TB8483CP, may break down.

(This is because the TB6520P/PG output is uncertain and the overcurrent limiting function becomes unable to

work.)

• About the TB6520P/PG DUTY input

When the DUTY pin is open, the duty cycle is full (100%).

If the motor with the TA8483CP connected to it is made to run without turning on the power supply voltage, the

induced voltage in the motor wraps around into the TB6520P/PG, causing it to malfunction, which in turn may

break down the TA8483CP.

Make sure the DUTY pin is pulled low via a resistor (approx. 100 kΩ).

• About external diode

For reason of PWM control, when PWM turns off, a regenerative current flows in the lower

−side diodes at the

output stage.

Always be sure to attach an external diode. This external diode must have a sufficient current capacity to

satisfy the maximum value of the motor current. Another thing to be noted is that a through current flows

depending on the diode's reverse recovery time.

TOSHIBA recommends attaching a schottky diode (2GWJ42 or equivalent).

TA8483CP output (lower side)

+

−