AMIS30623C623BRG Datasheet, PDF (31/61 Pages) ON Semiconductor – Micro-stepping Motor Driver

AMIS−30623
Motordriver
Current Waveforms in the Coils
Figure 17 below illustrates the current fed to the motor coils by the motordriver in half−step mode.
Ix
Coil X
Iy
t
Coil Y
Figure 17. Current Waveforms in Motor Coils X and Y in Halfstep Mode
Whereas Figure 18 below shows the current fed to the coils in 1/16^th micro stepping (1 electrical period).
Coil X
Iy
Ix
t
Coil Y
Figure 18. Current Waveforms in Motor Coils X and Y in 1/16^th Micro−Step Mode
PWM Regulation
In order to force a given current (determined by <Irun>
or <Ihold> and the current position of the rotor) through
the motor coil while ensuring high energy transfer
efficiency, a regulation based on PWM principle is used. The
regulation loop performs a comparison of the sensed output
current to an internal reference, and features a digital
regulation generating the PWM signal that drives the output
switches. The zoom over one micro−step in the Figure 18
above shows how the PWM circuit performs this regulation.
To reduce the current ripple, a higher PWM frequency is
selectable. The RAM register PWMfreq is used for this.
Table 22. PWM FREQUENCY SELECTION
PWMfreq
Applied PWM Frequency
0
22,8 kHz
1
45,6 kHz
PWM Jitter
To lower the power spectrum for the fundamental and
higher harmonics of the PWM frequency, jitter can be added
to the PWM clock. The RAM register <PWMJEn> is used
for this.
Table 23. PWM JITTER SELECTION
PWMJEn
Status
0
Single PWM frequency
1
Added jitter to PWM frequency
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