A4980LP View Datasheet(PDF) - Allegro MicroSystems
Part Name
Description
MFG CO.
'A4980LP' PDF : 44 Pages View PDF
A4980
Automotive, Programmable Stepper Driver
Application Information
Motor Movement Control
The A4980 provides two independent methods to control the
movement of a stepper motor. The simpler is the Step and Direc-
tion method, which only requires two control signals to control
the stepper motor in either direction. The other method is through
the serial interface, which provides more flexible control capa-
bility. Both methods can be used together (although it is not
common), provided the timing restrictions of the STEP input in
relation to the STRn input are preserved.
Phase Table and Phase Diagram
The key to understanding both of the available control methods
lies in understanding the Phase Current table (table 7). This table
contains the relative phase current magnitude and direction for
each of the two motor phases at each microstep position. The
maximum resolution of the A4980 is one-sixteenth microstep.
That is 16 microsteps per full step. There are 4 full steps per elec-
trical cycle, so the phase current table has 64 microstep entries.
The entries are numbered from 0 to 63. This number represents
IA
19 18 17 16 15 14 13
20
12
21
11
22
10
23
9
24
8
25
7
26
6
27
5
28
4
29
3
30
2
31
1
32
0
33
63 IB
34
62
35
61
36
60
37
59
38
58
39
57
40
41
56
55
42
54
43
53
44 45 46 47 48 49 50 51 52
the phase angle within the full 360° electrical cycle and is called
the Step Angle Number. This is illustrated in figure 5.
Figure 5 shows the contents of the phase current table as a phase
diagram. The phase B current, IB, from the phase current table, is
plotted on horizontal axis and the phase A current, IA, is plotted
on the vertical axis. The resultant motor current at each microstep
is shown as numbered radial arrows. The number shown corre-
sponds to the one-sixteenth microstep Step Angle Number in the
phase current table.
Figure 6 shows an example of calculating the resultant motor
current magnitude and angle for step number 28. The target is to
have the magnitude of the resultant motor current be 100% at all
microstep positions. The relative phase currents from the phase
current table are:
IA = 37.50%
IB = –92.19%
Assuming a full scale (100%) current of 1A means that the two
phase currents are:
IA = 0.3750 A
IB = -0.9219 A
24
25
26
27
28
29
30
31
32
IB28= – 92.19%
IA
28=
157.9°
IA28
=37.5%
IB
Figure 5. A4980 phase current table as a phase diagram; values shown
are referred to as the Step Angle Number
Figure 6. Calculation of resultant motor current
Allegro MicroSystems, Inc.
22
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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