FAN8741 Fairchild Semiconductor, FAN8741 Datasheet - Page 13

• Manufacturer Part Number: FAN8741
• Manufacturer: Fairchild Semiconductor

FAN8741/FAN8742 Rev. 1.0.1
Application Information
1. Torque Control & Output Current Control of 3-phase Bldc Motor
1) By amplifying the voltage difference between V
2) The output current (I
3) The clock generator always make the RS latch become set periodically, this enables the output driver’s on state, when the V
4) By the negative feedback loop, the sensed output voltage V
5) Commuting sequence is selected by hall sensor input, and the minimum hall input is 50mV.
6) The gain and limit currents are calculated as shown in the table below.(Gvo=V
7) Spindle block adopts 180
8) The range of the input voltage is as shown below when Rcs=0.33 , R
Current
SPIN
voltage(V
and the V
don’t need to change or modify their spindle motor.
R
Limit current
1.5
EXT1
[A]
AMP
AMP
---------- -
Rcs
0.5
Inside IC
10K
V
) which means input current command.
are equal the state becomes off.
REF
10K
O
) is converted into the voltage (V
Reverse
Torque AMP
o
commutation methodology which is fully compatible with a conventional BLDC spindle motor. Users
-50mV
Dead
zone-
Input/Output gain[A/V]
0
------------------------------------------ -
R
Dead
zone+
EXT1
V
50mV
AMP
10K
+
-
+
REF
Forward
IOMAX
10K
and SPIN from Servo IC(or DSP), the Torque AMP produces the input
CS
G
G
------------- -
R CS
MSP
) through the sense resistor (R
VO
Generator
CS
=G
Clock
13
VO
equals to the V
/ R
SPIN-V
CS
EXT1
------------------------------------------ -
R
EXT1
=0.
10K
REF
=L,open
R
S
MUTE2
MUTE2
AMP
AMP
+
=H
Q
10K
.
/(SPIN-V
Remark
CS
is gain scaler
SPIN > V
SPIN < V
) and compared with the V
REF
Commutator
Hall sensor
)=1[V/V]).
-
REF
REF
LPF
6
Forward rotation
Vcs
Reverse brake
Short brake
Short brake
Rotation
Driver
VM1
+
-
www.fairchildsemi.com
AMP
Io
Rcs
.
CS
M