
TB6539N/NG/F/FG
2006-05-09
9
Functional Description
Basic operation
On start-up, the motor is driven by the square-wave turn-on signal based on a positional signal. When
the positional signal reaches number of rotations f
= 5 Hz or higher, the rotor position is inferred from the
positional signal and a modulation wave is generated. The modulation wave and the triangular wave are
compared; the sine-wave PWM signal is then generated and the motor is driven.
From start to 5 Hz: When driven by square wave (120° turn-on), f
= fosc/(212 × 32 × 6)
5 Hz~: When driven by sine-wave PWM (180° turn-on)
When fosc = 4 MHz, approx. 5 Hz
Function to stabilize bootstrap voltage
(1)
When voltage instruction is input at Ve <= 0.2 V:
The lower transistor is turned on at the regular (carrier) cycle. (On duty is approx. 8%.)
(2)
When voltage instruction is input at Ve > 0.2 V:
During sine-wave drive, the drive signal is output as it is.
During square-wave drive, the lower transistor is forcibly turned on at the regular (carrier) cycle.
(On duty is approx. 8%.)
Note: At startup, to charge the upper transistor gate power supply, turn the lower transistor on for a fixed
time with Ve <
= 0.2 V.
Dead time function: upper/lower transistor output off-time
When the motor is driven by a sine-wave PWM, dead time is generated digitally in the IC to prevent any
short circuit caused by the simultaneous turning on of upper and lower external power devices.
Dead time: Td = 16/fosc (s)
When fosc = 4 MHz, approx. Td = 4 s.
fosc = reference clock (crystal oscillation)
Correcting lead angle
The lead angle can be corrected in the turn-on signal range from 0 to 58° in relation to the induced
voltage.
Analog input from LA pin (0 to 5 V divided by 32):
0 V
= 0°
5 V
= 58° (when more than 5 V is input, 58°)
Setting carrier frequency
This feature sets the triangular wave cycle (carrier cycle) necessary for generating the PWM signal.
(The triangular wave is used for forcibly turning on the lower transistor when the motor is driven by
square wave.)
Carrier cycle
= fosc/252 (Hz)
fosc = reference clock (crystal oscillation)
Switching the output of turn-on signal
This function switches the output of the turn-on signal between high and low.
Pin OS:
High
= active high
Low
= active low
Outputting reverse rotation detection signal
The direction of motor rotation is detected for every electrical angle of 360°. (The output is high
immediately after reset.)
The REV terminal increases to a 180° turn-on mode at the time of High-Z.
CW/CCW Pin
Actual Motor Rotating Direction
REV Pin
CW (forward)
High-Z
Low (CW)
CCW (reverse)
Low
CW (forward)
Low
High (CCW)
CCW (reverse)
High-Z