AMIS-30621 Datasheet, PDF (31/59 Pages) AMI SEMICONDUCTOR – LIN Microstepping Motordriver

AMIS−30621
Motordriver
Current Waveforms in the Coils
Figure 18 below illustrates the current fed to the motor coils by the motor driver in half−step mode.
Ix
Coil X
Iy
t
Coil Y
Figure 18. Current Waveforms in Motor Coils X and Y in Halfstep Mode
Whereas Figure 19 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 19. 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 19
above shows how the PWM circuit performs this regulation.
Motor Starting Phase
At motion start, the currents in the coils are directly
switched from <Ihold> to <Irun> with a new
sine/cosine ratio corresponding to the first half (or micro−)
step of the motion.
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