AMIS-30521 AMI Semiconductor, Inc., AMIS-30521 Datasheet - Page 9

• Manufacturer Part Number: AMIS-30521
• Description: Micro-stepping Motor Driver
• Manufacturer: AMI Semiconductor, Inc.

AMIS-30521 Micro-stepping Motor Driver
8.2.2. Automatic Duty Cycle Adaptation
Incase the supply voltage is lower than 2*Bemf, then the duty cycle of the PWM is adapted automatically to >50% to maintain the
requested average current in the coils. This process is completely automatic and requires no additional parameters for operation. The
over-all current-ripple is divided by two if PWM frequency is doubled
8.3 Step Translator
8.3.1. Step Mode
The step translator provides the control of the motor by means of SPI register Stepmode: SM[2:0], SPI register DIRCNTRL, and input
pins DIR and NXT. It is translating consecutive steps in corresponding currents in both motor coils for a given step mode.
One out of seven possible stepping modes can be selected through SPI-bits SM[2:0]
SM[2:0])
the step mode, the translator jumps to position
subsequent translator positions are all in the same column and increased or decreased with 1.
the output current versus the translator position.
As shown in
exception: uncompensated half step. In this step mode the currents are not regulated to a fraction of Imax but are in all intermediate
steps regulated at 100 percent. In the (I
Umcompensated Half StepSM[2:0] = 101 lists the output current versus the translator position for this case.
Table 9: Square Translator Table for Umcompensated Half StepSM[2:0] = 101
AMI Semiconductor – June 2007, M-20683-001
www.amis.com
After power-on or hard reset, the coil-current translator is set to the default 1/32 micro-stepping at position ‘0’. Upon changing
Uncompensated Half-Step
Figure 8
Stepmode ( SM[2:0] )
Icoil
101
the output current-pairs can be projected approximately on a circle in the (I
0*
1
2
3
4
5
6
7
Duty Cycle
T
< 50%
PWM
Actual value
x
,I
y
) plane the current-pairs are projected on a square.
Duty Cycle >50%
Figure 7: Automatic Duty Cycle Adaptation
0*
Coil x
-100
-100
-100
100
100
100
0
0
% of Imax
of the corresponding stepping mode. When remaining in the same step mode,
Coil y
-100
-100
-100
100
100
100
0
0
9
(Table 14: SPI Control Register
Duty Cycle < 50%
(Table 26: SPI Control Parameter Overview
Table 10:
Table 9:
x
1).
Set value
,I
y
) plane. There is, however, one
PC20070604.2
Circular Translator Table lists
Square Translator Table for
t
Data Sheet