FAN8741 Fairchild Semiconductor, FAN8741 Datasheet - Page 14

• Manufacturer Part Number: FAN8741
• Manufacturer: Fairchild Semiconductor

FAN8741/FAN8742 Rev. 1.0.1
2. Torque Control & Output Current Control Of Sled Motor(2-phase Step 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) To avoid output upper and lower transistor’s short through, a switch trick is needed. Turn on delay time is 1usec, so the phase
6) The gain and limit currents are calculated as shown in the table below.(Gvo=V
7)
SLIN1
(or SLIN2)
The range of the torque voltage is as shown below when Rcs=1W, R
the input voltage(V
and the V
delay time,when changing the current direction, is 1usec.
Torque limit current
R
EXT1
AMP
are equal the state becomes off.
0.5
[A]
---------- -
Rcs
0.5
V
10K
Inside IC
REF
AMP
O
10K
) is converted into the voltage (V
) which means input current command.
Torque AMP
Reverse
-15mV
V
Dead
zone-
AMP
Input/Output gain[A/V]
REF
+
-
0
I
OMAX
Dead
zone+
and SLIN1(or SLIN2) from Servo IC(or DSP), the Torque AMP produces
------------------------------------------ -
R
EXT1
15mV
CS
10K
) through the sense resistor (R
Forward
+
CS
Generator
10K
Clock
14
equals to the V
G
G
------------- -
R
EXT1
MSL
VO
CS
=G
=0 .
VO
/ R
R
S
AMP
AMP
CS
Q
.
/[SLIN1(or SLIN2)-V
SLIN1(or SLIN2)-V
------------------------------------------ -
R
EXT1
CS
) and compared with the V
10K
+
10K
Drive Logic
LPF
Remark
REF
is gain scaler
]=1[V/V]
REF
4
Vcs
Driver
VM2
www.fairchildsemi.com
+
-
AMP
Io
Rcs
.
CS
M