Data Sheet
SINGLE PHASE FULL WAVE DIRECT PWM MOTOR DRIVER
AM4961
Operating Diagram
VPWM adjustable Voltage
Lowest speed setting voltage
fOSC=25kHz (COSC=100pF)
Vosc
VMIN Voltage
COSC Output
Vosc
Low Speed
High Speed
PWM Variable
VCC
0V
FG Output
Figure 10. Operating Diagram of AM4961 (Note 6)
Note 6:
1. Low Speed Setting Mode
When VPWM voltage is higher than VMIN pin voltage,
motor speed is settable by VMIN pin voltage. The mini-
mum drive duty cycle is settable by comparing COSC
oscillating voltage and VMIN pin voltage.
VPWM voltage is decided by variation of PWM duty.
2. Variable Speed Setting Mode
At a certain PWN duty, when VPWM voltage is lower than
the low side of COSC output voltage, the motor will run at
full speed.
When VPWM voltage is lower than VMIN pin voltage,
PWM control system works by comparing VPWM voltage
and COSC voltage. If VPWM voltage is higher, the ON
duty cycle of the upper side transistors will be minimized
and motor speed becomes lower. Vice versa.
3. Full Speed Rotation Mode
Jun. 2008 Rev. 2. 2
BCD Semiconductor Manufacturing Limited
11
BCDSEMI [ BCD SEMICONDUCTOR MANUFACTURING LIMITED ]
