SLLU363 may 2023 MCF8315A
The Initial Speed Detection (ISD) function is used to identify the initial condition of the motor. Prioritize knowing the initial condition of the motor for reliable resynchronization. Motor resynchronization failures can occur when the device attempts to start the motor while the motor is coasting or spinning in the direction opposite to the intended direction of spin. Motors can coast in applications that require frequent motor starts and stops, or if the motor Is being forced externally or if there is a power interruption. Motors can spin in the direction opposite to the intended direction of spin if motor phase wires are connected to OUTA, OUTB and OUTC in wrong sequence or when wrong direction command is issued. Motors with higher inertia coast for a longer period of time. The recommendation is to have ISD enabled in applications that require frequent motor starts and stops and use higher inertia motors.
For example, ceiling fan motors have higher inertia due to the fan blades and can coast for long time before stopping.
Step 1: Enable ISD [ISD_EN]
Step 2: Enable Motor ISD Resynchronize [RESYNC_EN]
Follow the below recommendations if the motor fails to startup.
Increase the Motor Stationary BEMF Threshold [STAT_DETECT_THR].
Increase the Motor Stationary Persistence Time [ISD_STOP_TIME].
Increase the Motor Run Persistence Time [ISD_RUN_TIME].
Increase the Minimum speed threshold to resynchronize to closed loop