TC78H600FNG/FTG
2012-09-05
12
PWM control function
Applying a PWM signal to the PWM pin allows motor speed control.
(PWM drive can be operated by inputting PWM signal to IN1 and IN2 pins without using PWM pin.)
The IC enters CW (CCW) mode and short brake mode alternately in PWM current control.
To prevent shoot-through current caused by simultaneous conduction of upper and lower transistors in the
output stage, a dead time is internally generated when switching the upper and lower transistors.
Therefore, synchronous rectification for high efficiency in PWM current control can be achieved without an
off-time that is generated via an external input.
Even when toggling between each mode (CW, CCW, and short brake), the off-time is not required due to the
internally generated dead time.
Design target value:
Dead time, PWM ON→OFF: t2=300ns
PWM OFF→ON: t4=300ns
PWM ON
t5
Vcc
M
GND
OUT1
Vcc
M
GND
PWM OFF
t3
OUT1
Vcc
M
GND
PWM ON
t1
OUT1
Vcc
M
GND
PWM ON → OFF
t2 = 300 ns (typ.)
OUT1
Vcc
M
GND
PWM OFF → ON
t4 = 300 ns (typ.)
OUT1
RSGND
Vcc
Waveform of
output voltage
(AO1)
t1
t2
t3
t5
t4
