MCT8315A has the capability to accelerate a motor from 0 to 100% speed within 50ms. This will only work on low inertia motors which are capable of this level of acceleration. In order to achieve fast start-up, the commutation instant detection needs to be configured to hybrid mode by setting INTEG_ZC_METHOD to 1b. In the hybrid mode, the commutation instant is determined by using back-EMF integration at low-medium speeds and by using built-in comparators (BEMF zero crossing) at higher speeds. MCT8315A automatically transitions between back-EMF integration and comparator based commutation depending on the motor speed as shown in Figure 7-36. The duty cycles for commutation method transition at lower speeds are directly configured by INTEG_DUTY_THR_LOW and INTEG_DUTY_THR_HIGH and at higher speeds are indirectly configured by INTEG_CYC_THR_LOW and INTEG_CYC_THR_HIGH. These duty cycles should be configured to provide a sufficient hysteresis band to avoid repeated commutation method transitions near threshold duty cycles. The BEMF threshold values used to determine the commutation instant in the back-EMF integration method are configured by BEMF_THRESHOLD1 and BEMF_THRESHOLD2.

Figure 7-36 Commutation Method Transition