L6258EP_07 STMICROELECTRONICS [STMicroelectronics], L6258EP_07 Datasheet - Page 18

• Manufacturer Part Number: L6258EP_07
• Description: PWM controlled high current DMOS universal motor driver
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

PWM current control loop
3.3
18/32
Moreover, having the two references Tri_0 and Tri_180 a triangular shape it is clear that the
transfer function of this block is a linear constant gain without poles and zeros.
Load attenuation
The load block is composed by the equivalent circuit of the motor winding (resistance and
inductance) plus the sense resistor.
We will considered the effect of the Bemf voltage of the motor in the next chapter.
The input of this block is the PWM voltage of the power amplifier and as output we have the
voltage across the sense resistor produced by the current flowing into the motor winding.
The relation between the two variable is:
so the gain of this block is:
where:
R
R
Because of the inductance of the motor L
L
S
= equivalent resistance of the motor winding
= sense resistor
Aload
dB
Fpole
ACload dB
=
ACload
V sense
ACpw
20
Fpole
=
⋅
--------------------------------------------- -
6,28
log
dB
=
=
----------------------- -
12
=
=
V sense
-------------------- -
=
⋅
----------------------
R L
0,33
---------------------------------- -
2π
v
+
V
20
12
-------------------------- -
20
12
out
1
L
out
+
0,33
, the load has a pole at the frequency:
⋅
⋅
⋅
⋅
R S
+
-------------------- -
R
log
10
log
1
0,33
L
=
⋅
=
L
–
+
2
---------------- -
----------------------
R L
L
3
R S
----------------------
R
–
R
1,6
⋅
31,4dB
L
R S
S
=
R S
+
24
+
163Hz
R S
R
=
S
29,5dB
L6258EP