SLLSFH8A August 2021 – December 2021 MCT8316A
Variable commutation can be configured by setting COMM_CONTROL to 01b. 120o commutation may result in acoustic noise due to the long Hi-Z period causing some torque ripple in the motor. In order to reduce this torque ripple and acoustic noise, the MCT8316A uses variable commutation to reduce the phase current ripple at commutation by extending 120o driving time and gradually decreasing duty cycle prior to entering Hi-Z state. In this mode, the phase is Hi-Z between 30o and 60o and this window size is dynamically adjusted based on speed. A smaller window size will typically give better acoustic performance. Figure 8-29 shows 150o commutation with 30o window size.
Different modulation modes are supported only with 120o commutation; variable commutation uses mixed modulation mode only.