AM4967GS BCDSEMI [BCD Semiconductor Manufacturing Limited], AM4967GS Datasheet - Page 10

• Manufacturer Part Number: AM4967GS
• Description: ADJUSTABLE-SPEED SINGLE-PHASE FULL-WAVE PRE-DRIVER FOR MOTOR
• Manufacturer: BCDSEMI [BCD Semiconductor Manufacturing Limited]

Operating Diagram
Note 3:
1. Minimum Speed Setting Mode (Stop Mode)
When fan rotate at low speed, its lowest speed is settable
by VMIN pin voltage. If not, fan motor stops.
2. Low Speed to High Speed Setting Mode
PWM control system works by comparing the voltage of
VPWM and COSC (1.0V to 3.0V). When VPWM voltage
is low, the transistors of the upper and lower side outputs
are ON. On contrary, when VPWM voltage is high, the
upper side transistors are OFF. And coil current re-circu-
lates in a lower side transistor. Therefore, as the VPWM
Jun. 2008 Rev. 1. 1
ADJUSTABLE-SPEED SINGLE-PHASE FULL-WAVE PRE-DRIVER FOR MOTOR
VPWM Voltage
VMIN Voltage
COSC Voltage
0V
RPM
FG
Figure 9. Operating Diagram 1 of AM4967 (Speed Control, Note 3)
Minimum Speed Setup
Rotation (Stop Mode)
ON-Duty-Small
f
OSC
=30kHz (C
Low
Speed
OSC
=220pF)
10
PWM Adjustable
Speed
voltage becomes lower, output ON duty becomes large.
Sequentially, coil current increases and the motor runs at
high speed which is monitored by FG output while rota-
tion-stop state is monitored by RD output.
3. Full Speed Rotation Mode
When VPWM voltage drops to 1.0V or lower, motor fan
will run at full speed. (If the speed is not controlled,
V
PWM
=GND)
ON-Duty-Large
BCD Semiconductor Manufacturing Limited
High
Speed
Preliminary Datasheet
Full Speed
AM4967
3.0V
1.0V