SLOSE51A June   2020  – December 2020 DRV8428E

ADVANCE INFORMATION  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1. 5.1 Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
      1. 6.5.1 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagrams
    3. 7.3 Feature Description
      1. 7.3.1 PWM Motor Drivers
      2. 7.3.2 Bridge Control
      3. 7.3.3 Current Regulation, Off-time and Decay Modes
        1. 7.3.3.1 Mixed Decay
        2. 7.3.3.2 Smart tune Dynamic Decay
        3. 7.3.3.3 Smart tune Ripple Control
        4. 7.3.3.4 Blanking time
      4. 7.3.4 Linear Voltage Regulators
      5. 7.3.5 Logic and Seven-Level Pin Diagrams
      6. 7.3.6 Protection Circuits
        1. 7.3.6.1 VM Undervoltage Lockout (UVLO)
        2. 7.3.6.2 Overcurrent Protection (OCP)
        3. 7.3.6.3 Thermal Shutdown (OTSD)
        4. 7.3.6.4 Fault Condition Summary
    4. 7.4 Device Functional Modes
      1. 7.4.1 Sleep Mode (nSLEEP = 0)
      2. 7.4.2 Operating Mode (nSLEEP = 1)
      3. 7.4.3 Functional Modes Summary
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Current Regulation
        2. 8.2.2.2 Power Dissipation and Thermal Calculation
          1. 8.2.2.2.1 Application Curves
    3. 8.3 Alternate Application
      1. 8.3.1 Design Requirements
      2. 8.3.2 Detailed Design Procedure
        1. 8.3.2.1 Current Regulation
          1. 8.3.2.1.1 Stepper Motor Speed
            1. 8.3.2.1.1.1 Decay Modes
  9. 9 Power Supply Recommendations
    1. 9.1 Bulk Capacitance
  10. 10Layout
    1. 10.1 Layout Guidelines
      1. 10.1.1 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Related Links
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.3.3.2 Smart tune Dynamic Decay

The smart tune current regulation scheme is an advanced current-regulation control method compared to traditional fixed off-time current regulation schemes. Smart tune current regulation scheme helps the stepper motor driver adjust the decay scheme based on operating factors such as the ones listed as follows:

  • Motor winding resistance and inductance
  • Motor aging effects
  • Motor dynamic speed and load
  • Motor supply voltage variation
  • Low-current versus high-current dI/dt

GUID-E1F216D3-784D-4456-B388-41ACA1F5EB69-low.gifFigure 7-7 Smart tune Dynamic Decay Mode

Smart tune Dynamic Decay greatly simplifies the decay mode selection by automatically configuring the decay mode between slow, mixed, and fast decay. In mixed decay, smart tune dynamically adjusts the fast decay percentage of the total mixed decay time. This feature eliminates motor tuning by automatically determining the best decay setting that results in the lowest ripple for the motor.

The decay mode setting is optimized iteratively each PWM cycle. If the motor current overshoots the target trip level, then the decay mode becomes more aggressive (add fast decay percentage) on the next cycle to prevent regulation loss. If a long drive time must occur to reach the target trip level, the decay mode becomes less aggressive (remove fast decay percentage) on the next cycle to operate with less ripple and more efficiently. On falling steps, smart tune Dynamic Decay automatically switches to fast decay to reach the next step quickly.

Smart tune Dynamic Decay is optimal for applications that require minimal current ripple but want to maintain a fixed frequency in the current regulation scheme.