SLVAFO8A April   2024  – May 2024 DRV8214 , DRV8234

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction: Need for Sensorless Designs
  5. 2Ripple Counting − Concept
    1. 2.1 Ripple Counting Algorithm Details
  6. 3Case Study: Robotic Wheel Drive
    1. 3.1 Robotic Wheel Motor Operating Conditions
    2. 3.2 Tuning Parameters for Ripple Counting
      1. 3.2.1 Resistance Parameters
      2. 3.2.2 KMC and KMC_SCALE
        1. 3.2.2.1 Tuning KMC_SCALE
        2. 3.2.2.2 Tuning KMC
    3. 3.3 Robotic Wheel Motor with Ripple Counting
      1. 3.3.1 Inrush and Steady State Performance
        1. 3.3.1.1 Motor Speed Calculation
      2. 3.3.2 Soft Start
      3. 3.3.3 Loaded Conditions
  7. 4Challenges and Workarounds
    1. 4.1 Low Average Currents
    2. 4.2 Motor Inertia During Stop
    3. 4.3 Inrush
    4. 4.4 High Load Conditions
  8. 5Summary
  9. 6References
  10. 7Revision History

1 Introduction: Need for Sensorless Designs

Brushed DC motors require the knowledge of real-time motor speed, voltage, position, temperature, etc. for functioning in a closed loop system. While existing drivers integrate current, voltage, and temperature sensing, speed and position sensing require the use of external sensors like optical encoders and hall effect based sensors. This leads to:

  • Increase in design complexity
  • Increase in BOM count
  • Increase in BOM cost
  • Greater risk of failure due to added components, leading to overall reduced reliability

DRV8214 and DRV8234 implement an integrated ripple counting algorithm that enables sensorless speed and position sensing. This leads to significant system level benefits. Parameters can be tuned through I2C to achieve high accuracy results.