AMIS-30621 datasheet(34/43 Pages) AMI

34 / 43 page

9.2.3 Motordriver

9.2.3.1 Current Waveforms in the Coils

The figure below illustrates the current fed to the motor

coils by the motordriver in half-step mode.

9.2.3.2 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 above shows

how the PWM circuit performs this regulation.

9.2.3.3 Motor Starting Phase

At motion start, the currents in the coils are directly

switched from Ihold to Irun with a new sine/cos ratio

corresponding to the first half (or micro) step of the motion.

Whereas the figure below shows the current fed to one coil

in 1/16th microstepping (1 electrical period).

AMI Semiconductor- Rev. 1.4

www.amis.com

AMIS-30621 LIN Microstepping Motordriver

Data Sheet

AMIS-30621 Datasheet(PDF) 34 Page - AMI SEMICONDUCTOR