FAN8741 Fairchild Semiconductor, FAN8741 Datasheet - Page 16

• Manufacturer Part Number: FAN8741
• Manufacturer: Fairchild Semiconductor

FAN8741/FAN8742 Rev. 1.0.1
5. Reverse Rotation Prevention(Spindle)
1) As in the state of the forward rotation, the D-F/F output, Q is HIGH and the motor rotates normally. At this state, if the control
input is changed such that VREF>SPIN, then the motor rotates slowly by the reverse commutation in the driver. When the
motor begins to rotate in the reverse direction, the D-F/F output becomes Low and the OR Gate output becomes Low. This
prevents the motor from continuing to rotate in the reverse direction. This operation principle is shown in the following table
and flow chart.
VREF
SPIN
HW+
HV+
HW-
HV-
the output power stage equal to the short brake which is lower ,and three power transistors are fully turned on.
Rotation
Forward
Reverse
+
+
+
-
-
-
Power stage remains in short brake scheme until forward rotation command is received.
At the moment that the motor rotates in reverse, the reverse rotation preventer makes
Rotating speed is decreased due to reverse torque at VREF>SPIN
and appropriate mute combination. (Motor still rotates forward)
HV
Motor rotates in reverse for short time due to motor inertia
CK
H
D
L
D-F/F
Q
Forward rotation at VREF< SPIN
H L
H L
HW
A
Low Active
16
D-F/F
(Q)
H
L
Controller
Current
Sense
Amp
Gain
V
Reverse Rotation Preventer
REF
Forward
<SPIN
-
Driver
Brake and Stop
V
REF
www.fairchildsemi.com
>SPIN
-
M