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

1 Introduction

Pre-startup refers to the stage of motor operation when the initial speed, position and direction are determined by sensing the three phase voltages when a motor run command is received.

The initial speed detection(ISD) module is used to identify the initial state of the motor and is enabled by setting ISD_EN to 1b. If the motor is coasting and sufficient back EMF is available to be sensed, the motor can be resynchronized and driven to set reference directly.

ISD can be disabled by setting ISD_EN to 0b. If ISD is disabled, the MCx83xx does not perform the initial speed detection and proceeds to the brake routine if enabled before startup irrespective of motor initial state.

MCF83xx Pre-startup Flow Diagram Figure 1-1 MCF83xx Pre-startup Flow Diagram
Note: There are minor differences to the pre-startup routine in MCT83xx but majority of this application note is applicable to the MCT83xx devices also.

Notable differences in the MCT83xx pre-startup flow includes (but not limited to):

  • Absence of DIR_CHANGE_MODE: If RVS_DR_EN is set, state machine tries to reverse spin direction by decelerating to zero speed before accelerating in opposite direction. Else, motor is coasted and brake (if enabled) is applied to bring motor to standstill before accelerating in opposite direction.
  • Presence of a separate startup brake: Even when motor is detected to be stationary, the motor can still be rotating very slowly or oscillating. A startup brake is available that can be applied to bring motor to standstill. This can be configured to be different brake time than the regular brake. Generally, startup brake time is much less than regular brake time.
  • Since BEMF can be sensed in MCT83xx devices due to availability of floating phase, the threshold to resync is based on BEMF voltage magnitude unlike MCF83xx devices where the threshold is configured as a % of MAX_SPEED.