SLVSA73F April   2010  – July 2014 DRV8825

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Simplified Schematic
  5. 5 Revision History
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 Handling Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Timing Requirements
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 PWM Motor Drivers
      2. 8.3.2 Current Regulation
      3. 8.3.3 Decay Mode
      4. 8.3.4 Blanking Time
      5. 8.3.5 Microstepping Indexer
      6. 8.3.6 nRESET, nENBL, and nSLEEP Operation
      7. 8.3.7 Protection Circuits
        1. 8.3.7.1 Overcurrent Protection (OCP)
        2. 8.3.7.2 Thermal Shutdown (TSD)
        3. 8.3.7.3 Undervoltage Lockout (UVLO)
    4. 8.4 Device Functional Modes
      1. 8.4.1 STEP/DIR Interface
      2. 8.4.2 Microstepping
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Stepper Motor Speed
        2. 9.2.2.2 Current Regulation
        3. 9.2.2.3 Decay Modes
      3. 9.2.3 Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Bulk Capacitance
    2. 10.2 Power Supply and Logic Sequencing
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
    3. 11.3 Thermal Protection
      1. 11.3.1 Power Dissipation
      2. 11.3.2 Heatsinking
  12. 12Device and Documentation Support
    1. 12.1 Trademarks
    2. 12.2 Electrostatic Discharge Caution
    3. 12.3 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

10 Power Supply Recommendations

The DRV8825 is designed to operate from an input voltage supply (VMx) range between 8.2 and 45 V. Two
0.1-µF ceramic capacitors rated for VMx must be placed as close as possible to the VMA and VMB pins respectively (one on each pin). In addition to the local decoupling caps, additional bulk capacitance is required and must be sized accordingly to the application requirements.

10.1 Bulk Capacitance

Bulk capacitance sizing is an important factor in motor drive system design. It is dependent on a variety of factors including:

  • Type of power supply
  • Acceptable supply voltage ripple
  • Parasitic inductance in the power supply wiring
  • Type of motor (brushed DC, brushless DC, stepper)
  • Motor startup current
  • Motor braking method

The inductance between the power supply and motor drive system will limit the rate current can change from the power supply. If the local bulk capacitance is too small, the system will respond to excessive current demands or dumps from the motor with a change in voltage. You should size the bulk capacitance to meet acceptable voltage ripple levels.

The data sheet generally provides a recommended value but system level testing is required to determine the appropriate sized bulk capacitor.

app_motor_drive_LVSA73.gifFigure 11. Setup of Motor Drive System With External Power Supply

10.2 Power Supply and Logic Sequencing

There is no specific sequence for powering-up the DRV8825. It is okay for digital input signals to be present before VMx is applied. After VMx is applied to the DRV8825, it begins operation based on the status of the control pins.