L6223A ST Microelectronics, Inc., L6223A Datasheet - Page 12

• Manufacturer Part Number: L6223A
• Description: Dmos Programmable High Speed Unipolar Stepper Motor Driver
• Manufacturer: ST Microelectronics, Inc.

L6223A
L6223A Operating Configuration vs. 6bits Shift Register Programming (Continued)
APPLICATION INFORMATION
Single Device Application
Figure 10 shows a typical Single Device Applica-
tion. With the shown external RC network, the
higher chopping frequency is 20 kHz.
In the figure 11, 12 and 13 are shown the wave-
forms required to drive the motor in Half/Full Step
in FULL MODE OPERATING (FMO) and SIMPLI-
FIED MODE OPERATING (SMO). The sense re-
sistor defines the total motor current. This means
that when two phases are ON, the sense current
is two times the phase current. In this case the
sense resistor value is R
is the reference voltage and I
We have supposed that the phase current is of
the same intensity in the two phases. When only
one phase in ON, the current flowing in the sens-
ing resistor is the phase current: this occurs in
half step driving mode. The Figures 14 and 15
show the envelope of the sensing voltage in full
and half step respectively.
When current imbalance is not considered, this
12/33
Nr
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
C5
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
C4
SHIFT REGISTER bITS
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
C3
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
S
= (V
C2
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
P
the phase current.
ref
/2I
C1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
p
), where V
C0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
ref
Full/Simpl.
Operation
Mode
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
F
envelope represents the current level 2I
led by the chopping when L6223A is working at
100% of current; in full step this level is constant
while in half step two different levels are present
(Figure 15). Actually, in full step two phases are
always ON, and the chopping current level can be
changed only by the controller. In half step when
two phases are ON and L6223A is working at
nominal current level (2I
phase is ON, L6223A selects automatically the
reduced current. This level depends upon the pro-
gramming bits. In Figure 15 the higher level rep-
resents the chopping at nominal value (two
phases ON), the lower level the chopping at the
reduced current (one phase ON). The negative
peak shown in the figures represents the fast cur-
rent recirculation at the phase change.
Fig. 15 shows also what happens when the re-
duced current level selected is at 70% of the
nominal value. The motor torque is proportional to
the vectorial sum of the phase currents: it can be
seen that the unipolar stepper motor control actu-
ated by L6223A in half step is at constant torque
but not at constat current.
Close Loop
Frequency
(kHz)
20
20
20
20
20
20
20
20
20
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
Open Loop
DISABLED
DISABLED
DISABLED
DISABLED
DISABLED
DISABLED
DISABLED
DISABLED
t
(ON)
p
100
100
100
100
100
50
50
50
50
75
75
75
75
50
50
50
50
), but when only one
[%]
Close Loop
Level [%]
Current
85%
40%
70%
55%
85%
40%
70%
55%
85%
40%
70%
55%
85%
40%
70%
55%
85%
40%
70%
55%
85%
40%
70%
55%
85%
p
control-