SINGLE PHASE FULL WAVE DIRECT PWM MOTOR DRIVER

AM4961

Data Sheet

10

May. 2011 Rev. 2. 4

BCD Semiconductor Manufacturing Limited

Operating Diagram

Note 5:

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

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

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.

Figure 10. Operating Diagram of AM4961 (Note 5)

Lowest speed setting voltage

VPWM adjustable Voltage

f

VMIN Voltage

COSC Output

Low Speed

PWM Variable

High Speed

V

CC

0V

FG Output

V

osc

V

osc