tb6548f TOSHIBA Semiconductor CORPORATION, tb6548f Datasheet - Page 4

• Manufacturer Part Number: tb6548f
• Description: Three-phase Full-wave Pwm Sensorless Controller For Brushless Dc Motors
• Manufacturer: TOSHIBA Semiconductor CORPORATION

Functional Description
1. Sensorless Drive
2. Starting commutation frequency
3. PWM Control
Pin No.
21
22
23
24
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.
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).
drive the brushless DC motor.
the number of counter bit (within the IC).
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.
the motor and in accordance to the switching characteristics of the drive circuit.
positional detection cannot be performed with 0% duty or 100% duty.
duty is 99%.
On receipt of PWM signal start instruction turn-in signal for forcible commutation (commutation
When signals indicating positive or negative for pin voltage (including induced voltage) for each phase
Thereafter turn-on signal is formed according to the induced voltage contained in the pin voltage so as to
The forcible commutation frequency at the time of start is determined by the resonator’s frequency and
The forcible commutation frequency at the time of start can be adjusted using inertia of the motor and
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
Because positional detection is performed in synchronization with the falling edges of PWM signal,
The voltage applied to the motor is duty 100% because of the storage time of the drive circuit even if the
Starting commutation frequency f
OUT_WN
OUT_WP
Symbol
WAVE
OC
Duty (min)
Duty (max)
I/O
O
O
I
I
W-phase upper turn-on signal output pin
•
•
W-phase lower turn-on signal output pin
•
•
Overcurrent signal input pin
•
•
Positional signal input pin
•
•
W-phase winding wire positive ON/OFF switching pin
ON: Low, OFF: High
W-phase winding wire negative ON/OFF switching pin
ON: High, OFF: Low
High on this pin can put constraints on the turn-on signal which is performing PWM
control.
Built-in pull-up resistor
Inputs majority logic synthesis signal of three-phase pin voltage.
Built-in pull-up resistor
st
= Resonator frequency f
(resonator pin and counter bit select pin)
4
Description
xt
/(6 × 2
250 ns
250 ns
(bit + 3)
)
bit = 14
2001-08-28
TB6548F