TB6537P/F

2003-02-20

5

Pin No.

TB6537P TB6537F

Symbol

I/O

Description

¾

20

NC

¾

Not connected

15

21

OUT_WP

O

W-phase upper turn-on signal output pin

· W-phase winding wire positive ON/OFF switching pin

· ON: Low, OFF: High

16

22

OUT_WN

O

W-phase lower turn-on signal output pin

· W-phase winding wire negative ON/OFF switching pin

· ON: High, OFF: Low

17

23

OC

I

Overcurrent signal input pin

· High on this pin can put constraints on the turn-on signal which is performing PWM

control.

· Built-in pull-up resistor

18

24

WAVE

I

Positional signal input pin

· Inputs majority logic synthesis signal of three-phase pin voltage.

· Built-in pull-up resistor

Functional Description

1.

Sensorless Drive

On receipt of PWM signal start instruction turn-in signal for forcible commutation (commutation

irrespective of the motor’s rotor position) is output and the motor starts to rotate. The motor’s rotation

causes induced voltage on winding wire pin for each phase.

When signals indicating positive or negative for pin voltage (including induced voltage) for each phase

are input on respective positional signal input pin, the turn-on signal for forcible commutation is

automatically switched to turn-on signal for positional signal (induced voltage).

Thereafter turn-on signal is formed according to the induced voltage contained in the pin voltage so as to

drive the brushless DC motor.

2.

The forcible commutation frequency at the time of start is determined by the resonator’s frequency and

the number of counter bit (within the IC).

bit = 14

The forcible commutation frequency at the time of start can be adjusted using inertia of the motor and

load.

· The forcible commutation frequency should be set higher as the number of magnetic poles increases.

· The forcible commutation frequency should be set lower as the inertia of the load increases.

3.

PWM Control

PWM signal can be reflected in turn-on signal by supplying PWM signal from external sources.

The frequency of the PWM signal shoud be set adequately high with regard to the electrical frequency of

the motor and in accordance to the switching characteristics of the drive circuit.

Because positional detection is performed in synchronization with the rising edges of PWM signal,

positional detection cannot be performed with 0% duty or 100% duty.

The voltage applied to the motor is duty 100% because of the storage time of the drive circuit even if the

duty is 99%.

Duty (max)

Duty (min)

250 ns

250 ns