SLLA663 March   2025 MCF8315A , MCF8315C , MCF8315C-Q1 , MCF8315D , MCF8316A , MCF8316C-Q1 , MCF8316D , MCF8329A , MCT8315A , MCT8316A , MCT8329A

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2End Application Configuration Recommendation
    1. 2.1 Resynchronization
    2. 2.2 Reverse Drive
    3. 2.3 Coasting (Hi-Z)
    4. 2.4 Startup Brake
    5. 2.5 Direction Change Mode
  6. 3Tuning Guidance
    1. 3.1 Initial Speed Detection Module
      1. 3.1.1 Initial Speed Detection
      2. 3.1.2 ISD Times
      3. 3.1.3 Stationary Detect Threshold
    2. 3.2 Resynchronization
      1. 3.2.1 Forward Drive Resync Threshold
      2. 3.2.2 Reverse Drive
      3. 3.2.3 Reverse Acceleration Parameters
      4. 3.2.4 Reverse Drive Current Limits
      5. 3.2.5 Reverse Drive Handoff Threshold
      6. 3.2.6 Reverse Drive Open Loop Deceleration (REV_DRV_OPEN_LOOP _DEC)
    3. 3.3 Coasting (Hi-Z)
    4. 3.4 Brake
      1. 3.4.1 Brake Config (BRK_CONFIG)
  7. 4Feature Availability of MCx Devices
    1. 4.1 FOC Family (MCF83xx devices)
    2. 4.2 TRAP Family (MCT83xx devices)
  8. 5Summary
  9. 6References

4.2 TRAP Family (MCT83xx devices)

TRAP (MCT83xx devices) family of devices have a sub-set of the FOC pre-start-up configurations. The reverse drive uses the open loop parameters instead of having separate configuration parameters.

Table 4-2 Trap Device Feature Availability
Device Family Features not Supported
MCT8316A TRAP
  1. FAST_ISD_EN
  2. ISD_STOP_TIME
  3. ISD_RUN_TIME
  4. ISD_TIMEOUT
  5. ISD_BEMF_FILT_ENABLE
  6. DIR_CHANGE_MODE
  7. REV_DRV_CONFIG
  8. REV_DRV_HANDOFF_THR
  9. REV_DRV_OPEN_LOOP_ACCEL_A1
  10. REV_DRV_OPEN_LOOP_ACCEL_A2
  11. REV_DRV_OPEN_LOOP_CURRENT
  12. REV_DRV_OPEN_LOOP_DEC
  13. BRK_CONFIG
  14. BRK_CURR_THR
  15. BRAKE_CURRENT_PERSIST
MCT8315A TRAP
  1. FAST_ISD_EN
  2. ISD_STOP_TIME
  3. ISD_RUN_TIME
  4. ISD_TIMEOUT
  5. ISD_BEMF_FILT_ENABLE
  6. DIR_CHANGE_MODE
  7. REV_DRV_CONFIG
  8. REV_DRV_HANDOFF_THR
  9. REV_DRV_OPEN_LOOP_ACCEL_A1
  10. REV_DRV_OPEN_LOOP_ACCEL_A2
  11. REV_DRV_OPEN_LOOP_CURRENT
  12. REV_DRV_OPEN_LOOP_DEC
  13. BRAKE_CURRENT_PERSIST
MCT8329A TRAP
  1. FAST_ISD_EN
  2. ISD_STOP_TIME
  3. ISD_RUN_TIME
  4. ISD_TIMEOUT
  5. ISD_BEMF_FILT_ENABLE
  6. DIR_CHANGE_MODE
  7. REV_DRV_CONFIG
  8. REV_DRV_HANDOFF_THR
  9. REV_DRV_OPEN_LOOP_ACCEL_A1
  10. REV_DRV_OPEN_LOOP_ACCEL_A2
  11. REV_DRV_OPEN_LOOP_CURRENT
  12. REV_DRV_OPEN_LOOP_DEC
  13. BRK_CONFIG
  14. BRK_CURR_THR
  15. BRAKE_CURRENT_PERSIST

Table 4-3 shows dependency of configuration on other configurations and impact of the configuration on motor operation

Table 4-3 Configuration With Dependency and Tradeoffs
Configuration Impact on Motor Operation Dependency
ISD_EN Reliable and fast motor startup based on the initial condition of the motor speed. None
FAST_ISD_EN TRADEOFF:
  • Initial current spikes possible due to inaccuracy in BEMF measured.
  • Possibility of reverse spinning observed in some cases.
  • ISD_EN = 1b
ISD_STOP_TIME TRADEOFF:
  • If persistence time is too high, the resyncing time increases.
  • If kept too low, the ISD robustness decreases.
  • ISD_EN = 1b
ISD_RUN_TIME
ISD_TIMEOUT TRADEOFF:
  • If timeout is too high, the ISD time increases
  • If kept too low, the ISD robustness decreases.
  • ISD_EN = 1b
ISD_BEMF_FILT_ENABLE Smoothens the sensed BEMF to maintain reliable speed and direction determination
  • ISD_EN = 1b
STAT_DETECT_THR TRADEOFF:
  • If set too high, device can be forced to go through brake at higher speed leading to higher brake currents.
  • If set too low, device can attempt to resync without sufficient BEMF leading to faults or ISD timeout
  • ISD_EN = 1b
RESYNC_EN = 1b Fastest possible start-up time if motor spinning in commanded direction.
  • ISD_EN = 1b
FW_DRV_RESYN_THR TRADEOFF:
  • If set too low, then device can try to enter closed loop with insufficient BEMF leading to faults.
  • If set too high, the device can try to drive motor in open loop instead of handing off to closed loop even when sufficient speed is available leading to reliability issues.
  • ISD_EN = 1b
  • RESYNC_EN = 1b
DIR_CHANGE_MODE If set to 1b, direction is changed through reverse drive by slowing down the motor to zero speed and reversing direction. Else, direction is changes through ISD state machine and if ISD is disabled, motor is stopped through brake before starting in commanded direction. None
RVS_DRV_EN Fastest possible start-up time in a controlled manner if motor spinning in opposite to commanded direction. Considered as a more controlled way to reduce the speed and reverse the motor.
  • ISD_EN = 1b
REV_DRV_CONFIG If REV_DRV_CONFIG = 1b, the motor changes the direction using reverse drive specific open loop parameters. Open loop parameters can be tuned to handle different dynamics from normal OL startup.
  • ISD_EN = 1b
  • RVS_DRV_EN = 1b
REV_DRV_HANDOFF_THR TRADEOFF:
  • If set too low, then device can fail to handover to open loop even with insufficient BEMF leading to faults.
  • If set too high, the device hands over to open loop instead of decelerating in closed loop even when sufficient BEMF is available. This results in longer open loop time and inefficient drive.
  • ISD_EN = 1b
  • RVS_DRV_EN = 1b
  • REV_DRV_CONFIG = 1b

REV_DRV_OPEN_LOOP_ACCEL_A1

 TRADEOFF:
  • If set too high, the device can try to decelerate the motor too fast and unable to spin up and loose sync.
  • If set too low, the drive can look jerky as the motor speed reduces.
  • ISD_EN = 1b,
  • RVS_DRV_EN = 1b
  • REV_DRV_CONFIG = 1b

REV_DRV_OPEN_LOOP_ACCEL_A2

REV_DRV_OPEN_LOOP_CURRENT

 TRADEOFF:
  • If set too high, heats up the motor and reduces the efficiency of the drive as more than required current is pushed into the motor.
  • If set too low, the drive cannot decelerate the motor and accelerate the motor in the opposite direction in a controlled manner, which can lead to vibrations or faults.
  • ISD_EN = 1b
  • RVS_DRV_EN = 1b
  • REV_DRV_CONFIG = 1b
REV_DRV_OPEN_LOOP _DEC If some external factor is affecting the drive then the rate of deceleration and acceleration needs to be different from the corresponding values at open loop startup.
  • ISD_EN = 1b
  • RVS_DRV_EN = 1b
HIZ_EN Gives the motor time to coast and slow down before applying brake and proceeding to motor startup.
  • ISD_EN = 1b
  • (RVS_DRV_EN = 1b or RESYNC_EN = 1b)
HIZ_TIME As energy is lost only through friction, speed falls slowly and a higher setting for high inertia motor is recommended.
  • ISD_EN = 1b
  • (RVS_DRV_EN = 1b or RESYNC_EN = 1b)
  • HIZ_EN = 1b
BRAKE_EN Makes sure motor is stationary before motor startup by braking before motor startup. None
BRK_MODE This method involves turning ON all low-side/high-side FETs at once to allow current to recirculate through the low-side/high-side MOSFETs. Doing this effectively shorts the back emf, quickly lowering the motor speed and dissipating the motor mechanical energy. Braking adds to thermal stress on the FETs and care to be taken to avoid frequent braking that can result in thermal shutdown
  • BRAKE_EN = 1b
BRK_CONFIG Time based brake applies brake for a fixed time irrespective of the motor speed. Current based brake allows brake to be applied only till motor BEMF falls indicated by current falling below BRK_CURR_THR.
  • BRAKE_EN = 1b
  • BRK_TIME
  • BRK_CURR_THR
BRK_TIME If BRK_CONFIG = 0b, then device applies brake for BRK_TIME. If BRK_CONFIG = 1b, device applies brake till current falls below BRK_CURR_THR and BRK_TIME acts as a timeout incase current fails to fall below BRK_CURR_THR before BRK_TIME.
  • BRAKE_EN = 1b
BRK_CURR_THR If BRK_CONFIG = 1b, device applies brake till brake current falls below the BRK_CURR_THR.
  • BRAKE_EN = 1b
  • BRK_CONFIG = 1b
  • BRK_MODE = 1b
BRAKE_CURRENT_PERSIST TRADEOFF:
  • If set too low, drive can give false positive for current falling below threshold as brake current is sinusoidal.
  • If set too high, increases the brake exit time.
  • BRAKE_EN = 1b
  • BRK_CONFIG = 1b
  • BRK_CURR_THR
  • BRK_MODE = 1b