SLVAFF1 January   2023 DRV8452 , DRV8462


  1.   Abstract
  2.   Trademarks
  3. 1Power Efficiency of Stepper Motor Drivers
  4. 2Auto-Torque
    1. 2.1 Auto-Torque: Learning Principle
      1. 2.1.1 Configuring Auto-Torque Learning Routine
    2. 2.2 Current Control
      1. 2.2.1 Setting Current Control Parameters
    3. 2.3 PD Control Loop
    4. 2.4 Impact of Auto-Torque Tuning Parameters
      1. 2.4.1 Impact of Learning Parameters on Load Transient Response
      2. 2.4.2 Impact of ATQ_UL, ATQ_LL Hysteresis
      3. 2.4.3 Impact of Load Profile on Power Saving
      4. 2.4.4 Adaptive ATQ_UL, ATQ_LL
      5. 2.4.5 PD Parameter Dependency Curves
        1. Dependency on KP
        2. Dependency on KD and ATQ_D_THR
        3. Dependency on ATQ_FRZ and ATQ_AVG
        4. Dependency on ATQ_ERROR_TRUNCATE
      6. 2.4.6 ATQ_CNT at Different Motor Speeds
      7. 2.4.7 ATQ_CNT at Different Supply Voltages
      8. 2.4.8 Motor Temperature Estimation
    5. 2.5 Efficiency Improvement With Auto-Torque
  5. 3Case Studies
    1. 3.1 Application 1: ATM Machines
      1. 3.1.1 ATM Motor Operating Conditions
      2. 3.1.2 ATM Motor With Auto-Torque
    2. 3.2 Application 2: Textile Machines
      1. 3.2.1 Textile Motor Operating Conditions
      2. 3.2.2 Textile Motor With Auto-Torque
    3. 3.3 Application 3: Printer
      1. 3.3.1 Printer Motor With Auto-Torque
  6. 4Summary
  7. 5References


A stepper motor system is an open-loop position control system. The system controller or the motor driver IC has no information on how much load torque is being applied or what should be the optimal current for operation without step loss. Since the driver is imperceptive of the load torque demand, motors are generally driven at constant full-scale current which can sustain maximum load torque. However, the use of large operating current is needless at lighter loads as it results in unnecessary I2R losses. Apart from lowering overall system efficiency, high coil current leads to thermal issues due to motor heating reducing the durability and longevity of the motor.

Texas Instruments recently introduced the DRV8462, DRV8452 and DRV8461 stepper motor drivers, which include several new features including the auto-torque algorithm. Auto-torque boosts system efficiency by adjusting the stepper coil current automatically according to the load torque. Auto-torque does not require any external sensor. Instead, by monitoring the power delivered to the motor, it generates an internal signal which varies linearly with the load torque, with fast sensing capability. This application report aims to highlight the advantages of the auto-torque algorithm and how it can be tuned for maximum benefits.