SLVSAB7D May   2010  – December 2015 DRV8840

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  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
    6. 6.6 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 PWM Motor Driver
      2. 7.3.2 Bridge Control
      3. 7.3.3 Current Regulation
      4. 7.3.4 Decay Mode and Braking
      5. 7.3.5 Blanking Time
      6. 7.3.6 Protection Circuits
        1. 7.3.6.1 Overcurrent Protection (OCP)
        2. 7.3.6.2 Thermal Shutdown (TSD)
        3. 7.3.6.3 Undervoltage Lockout (UVLO)
    4. 7.4 Device Functional Modes
      1. 7.4.1 nRESET and nSLEEP Operation
  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 Sense Resistor
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
    1. 9.1 Bulk Capacitance Sizing
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 Thermal Considerations
      1. 10.3.1 Power Dissipation
      2. 10.3.2 Heatsinking
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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9 Power Supply Recommendations

The DRV8840 is designed to operate from an input voltage supply (VM) range from 8.2 V to 45 V. The device has an absolute maximum rating of 47 V. A 0.1-μF ceramic capacitor rated for VM must be placed at each VM pin as close to the DRV8840 as possible. In addition, a bulk capacitor must be included on VM.

9.1 Bulk Capacitance Sizing

Having appropriate local bulk capacitance is an important factor in motor drive system design.  It is generally beneficial to have more bulk capacitance, while the disadvantages are increased cost and physical size.

The amount of local capacitance needed depends on a variety of factors, including:

  • The highest current required by the motor system.
  • The power supply’s capacitance and ability to source current.
  • The amount of parasitic inductance between the power supply and motor system.
  • The acceptable voltage ripple.
  • The type of motor used (Brushed DC, Brushless DC, Stepper).
  • The 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.  When adequate bulk capacitance is used, the motor voltage remains stable and high current can be quickly supplied.

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

The voltage rating for bulk capacitors should be greater than the operating voltage, to provide margin for cases when the motor transfers energy to the supply.

DRV8840 ext_pwr_supply_lvsa74.gif Figure 10. Setup of Motor Drive System With External Power Supply