SLLU364 may   2023 MCT8315A

 

  1.   1
  2.   Abstract
  3. 1Revision History
  4.   Trademarks
  5. 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
  6. 3Essential Controls
    1. 3.1 Recommended Default Values based on application
    2. 3.2 Device and Pin Configuration
      1. 3.2.1 Speed input mode
    3. 3.3 Algorithm configuration – Motor speed
      1. 3.3.1 Maximum motor electrical speed (Hz)
    4. 3.4 Control Configuration
      1. 3.4.1 Cycle by cycle current limit (ILIMIT)
    5. 3.5 Testing for successful startup into closed loop
    6. 3.6 Fault handling
      1. 3.6.1 Abnormal Speed [ABN_SPEED]
      2. 3.6.2 Loss of Sync [LOSS_OF_SYNC]
      3. 3.6.3 No Motor Fault [NO_MTR]
      4. 3.6.4 Cycle by cycle current limit [CBC_ILIMIT]
  7. 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 Monitoring power supply voltage fluctuations for normal motor operation
    3. 4.3 Control configurations
      1. 4.3.1  Initial speed detection of the motor for reliable motor resynchronization
      2. 4.3.2  Unidirectional motor drive detecting backward spin
      3. 4.3.3  Preventing back spin of rotor during startup
      4. 4.3.4  Faster startup timing
      5. 4.3.5  Improving speed regulation
      6. 4.3.6  Stopping motor quickly
      7. 4.3.7  Faster deceleration
      8. 4.3.8  Preventing supply voltage overshoot during motor stop and deceleration
      9. 4.3.9  Protecting against rotor lock or stall condition
      10. 4.3.10 Maximizing thermal efficiency and increasing thermal performance
      11. 4.3.11 Mitigating Electromagnetic Interference (EMI)
      12. 4.3.12 Improving Motor efficiency
      13. 4.3.13 Limiting and regulating supply power

4.2.1 Tracking motor speed feedback in real time

MCT8315A device provides information about the motor speed through the frequency generator (FG) pin, which is also known as a TACH (tachometer) out. In MCT8315A, the FG pin behavior is configured through FG_CONFIG. Configure FG_SEL to output FG signal only in closed loop, both open loop and closed loop, or only in open loop for the first try. Configure FG_DIV to number of motor poles so that the FG output matches the motor mechanical speed in Hz.

When FG_CONFIG is configured to 0 (FG active as long as motor is driven), the FG output is active as long as MCT8315A is driving the motor. FG will not be active during a motor stop and coasting condition. In this mode, FG is released high when MCT8315A enters sleep or standby mode. This mode is useful in applications that require real time motor speed information as long as MCT8315A is driving the motor.

When FG_CONFIG is configured to 1 (FG active till BEMF drops below FG_BEMF_THR), MCT8315A provides FG output until BEMF falls below FG_BEMF_THR. The FG output will continue to indicate motor speed even if the motor is not being actively driven. This mode is useful in applications that require motor speed information above a certain speed, and rotor motion information during the coast and braking conditions.

For example, if the motor Ke is 5 mV/Hz and the application require measuring motor speed above 4 Hz, then the user can configure FG_BEMF_THR to 20 mV. Once when the motor speed reaches 4 Hz, the device will output FG as the BEMF voltage will be 20 mV at 4 Hz.