SLLU335A August   2021  – January 2022 MCF8316A

 

  1. 1Revision History
    1.     Trademarks
  2. 2Introduction
    1. 2.1 Hardware and GUI Setup
      1. 2.1.1 Jumper Configuration
      2. 2.1.2 External Connections
      3. 2.1.3 Connecting to the GUI
        1. 2.1.3.1 Connect to computer
        2. 2.1.3.2 Connect to the GUI
        3. 2.1.3.3 Verify Hardware Connection
  3. 3Essential Controls
    1. 3.1 Recommended Default Values
    2. 3.2 Device and Pin Configuration
      1. 3.2.1 Speed Input Mode
    3. 3.3 Control Configuration - Motor Parameters
      1. 3.3.1 Maximum Motor Electrical Speed (Hz)
    4. 3.4 Control configuration - Closed Loop
      1. 3.4.1 Current Limit for Torque PI Loop
    5. 3.5 Testing for Successful Startup into Closed Loop
    6. 3.6 Fault Handling
      1. 3.6.1 MPET IPD Fault [MPET_IPD_Fault]
      2. 3.6.2 MPET BEMF Fault [MPET_BEMF_Fault]
      3. 3.6.3 Abnormal BEMF Fault [ABN_BEMF]
      4. 3.6.4 Lock Current Limit [LOCK_LIMIT]
      5. 3.6.5 Hardware lock Current Limit [HW_LOCK_LIMIT]
      6. 3.6.6 No Motor Fault [NO_MTR]
  4. 4Basic Controls
    1. 4.1 Device and Pin Configuration
      1. 4.1.1 Power Saver or Sleep Mode for Battery Operated Applications
      2. 4.1.2 Direction and Brake Pin Override
    2. 4.2 System Level Configuration
      1. 4.2.1 Tracking Motor Speed Feedback in Real Time
      2. 4.2.2 Improving Acoustic Performance
      3. 4.2.3 Protecting the Power supply
      4. 4.2.4 Monitoring Power Supply Voltage Fluctuations for Normal Motor Operation
    3. 4.3 Control Configurations
      1. 4.3.1  Motor Parameter Estimation to Minimize Motor Parameter Variation Effects
      2. 4.3.2  Initial Speed Detection of the Motor for Reliable Motor Resynchronization
      3. 4.3.3  Unidirectional Motor Drive Detecting Backward Spin
      4. 4.3.4  Preventing Back Spin of Rotor During Startup
      5. 4.3.5  Faster Startup Timing
      6. 4.3.6  Gradual and Smooth Start up Motion
      7. 4.3.7  Improving Speed Regulation
      8. 4.3.8  Stopping Motor Quickly
      9. 4.3.9  Preventing Supply Voltage Overshoot During Motor Stop.
      10. 4.3.10 Protecting Against Rotor Lock or Stall Condition
      11. 4.3.11 Maximizing Thermal Efficiency and Increasing Thermal Performance
      12. 4.3.12 Mitigating Electromagnetic Interference (EMI)
      13. 4.3.13 Faster deceleration

4.2.3 Protecting the Power supply

Protecting the power supply from drawing higher current or potential voltage overshoots is important in battery operated applications or applications that do not have an internal overcurrent or overvoltage protection built into the power supply.

Step 1: When the load on the motor increases, device draws higher current from the power supply. For applications that may want to limit the current drawn from the power supply, it is recommended to Enable Bus current limit [BUS_CURRENT_LIMIT_ENABLE] and configure the Bus current limit [BUS_CURRENT_LIMIT] to protect the power supply from drawing higher current.

For example, it is required to limit the current drawn from power supplies such as batteries as the battery life depends on the charge or discharge cycles. Enabling bus current limit limits the power supply current by limiting the speed of the motor.

Step 2: When a command is issued for the motor to decelerate, based on the deceleration rate, the energy from motor may be pumped back to the power supply, increasing the supply voltage to possibly unsafe levels for electronics. Enable the Antivoltage surge [AVS] to protect the power supply from voltage overshoots which will override any deceleration limit set by any other register and automatically apply a safe deceleration rate.

Figure 4-3 shows overshoot in power supply voltage when AVS is disabled. Motor decelerates from 100% duty cycle to 10% duty cycle at a deceleration rate of 70,000 Hz/sec. Figure 4-4 shows no overshoot in power supply voltage when AVS is enabled.

Figure 4-3 Power Supply voltage and phase current waveform when AVS is disabled
Figure 4-4 Power Supply voltage and phase current waveform when AVS is enabled