Figure 7-19 shows the motor-start sequence implemented in the MCF8329A device.
Power-On StateThis is the initial state of the Motor Start Sequence (MSS). The MSS starts in this state on initial power-up or whenever the MCF8329A device comes out of standby or sleep mode.
DIR Change && DIR_CHANGE_MODE = 0b JudgementIn MCF8329A, if direction change command is detected and DIR_CHANGE_MODE is set to 0b during any state (including closed loop), the device re-starts the MSS.
ISD_EN JudgementAfter power-on, the MCF8329A MSS enters the ISD_EN judgement where it checks to see if the initial speed detect (ISD) function is enabled (ISD_EN = 1b). If ISD is disabled, the MSS proceeds directly to the BRAKE_EN judgement. If ISD is enabled, MSS advances to the ISD (Is Motor Stationary) state.
ISD StateThe MSS determines the initial condition (speed, direction of spin) of the motor (see Initial Speed Detect (ISD)). If motor is deemed to be stationary (motor BEMF < STAT_DETECT_THR), the MSS proceeds to BRAKE_EN judgement. If the motor is not stationary, MSS proceeds to verify the direction of spin.
Direction of Spin JudgementThe MSS determines whether the motor is spinning in the forward or the reverse direction. If the motor is spinning in the forward direction, the MCF8329A proceeds to the RESYNC_EN judgement. If the motor is spinning in the reverse direction, the MSS proceeds to the RVS_DR_EN judgement.
RESYNC_EN JudgementIf RESYNC_EN is set to 1b, MCF8329A proceeds to Speed > Open to Closed Loop Handoff (Re-sync) judgement. If RESYNC_EN is set to 0b, MSS proceeds to HIZ_EN judgement.
Speed > Open to Closed Loop Handoff (Re-sync) JudgementIf motor speed > FW_DRV_RESYN_THR, MCF8329A uses the speed and position information from the
ISD state to transition to the closed loop state (see Motor Resynchronization)
directly. If motor speed < FW_DRV_RESYN_THR, MCF8329A transitions to open
loop state.
RVS_DR_EN JudgementThe MSS checks to see if the reverse drive function is enabled (RVS_DR_EN = 1). If it is enabled, the MSS transitions to check speed of the motor in reverse direction. If the reverse drive function is not enabled, the MSS advances to the HIZ_EN judgement.
Speed > Open to Closed Loop Handoff (Reverse) JudgementThe MSS checks to see if the reverse speed is high enough for MCF8329A to decelerate in closed loop. Till the speed (in reverse direction) is high enough, MSS stays in reverse closed loop deceleration. If speed is too low, then the MSS transitions to reverse open loop deceleration.
Reverse Closed Loop, Open Loop Deceleration and Zero Speed CrossoverThe MCF8329A resynchronizes in the reverse direction, decelerates the motor in closed loop till motor speed falls below the handoff threshold. (see Reverse Drive). When motor speed in reverse direction is too low, the MCF8329A switches to open-loop, decelerates the motor in open-loop, crosses zero speed, and accelerates in the forward direction in open-loop before entering closed loop operation after motor speed is sufficiently high.
HIZ_EN JudgementThe MSS checks to determine whether the coast (Hi-Z) function is enabled (HIZ_EN =1). If the coast function is enabled, the MSS advances to the coast routine. If the coast function is disabled, the MSS advances to the BRAKE_EN judgement.
Coast (Hi-Z) RoutineThe device coasts the motor by turning OFF all six MOSFETs for a certain time configured by HIZ_TIME.
BRAKE_EN JudgementThe MSS checks to determine whether the brake function is enabled (BRAKE_EN =1). If the brake function is enabled, the MSS advances to the brake routine. If the brake function is disabled, the MSS advances to the motor start-up state (see Section 7.3.10.4).
Brake RoutineMCF8329A implements a brake by turning on all three low-side
MOSFETS for BRK_TIME.
Closed Loop StateIn this state, the MCF8329A drives the motor with FOC.
Note: User
should ensure adequate start up time to fully charge the bootstrap capacitors. One
way to charge the boot capacitor is by providing enough time with low side brake at
start up. Other ways is to use the bootstrap precharging routine. With ISD
operation, the device will initiate ISD only after bootstrap voltage crosses the
UVLO threshold.