SLVSD29 October   2015 DRV8704

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
    1.     Device Images
      1.      Simplified Schematic
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    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
    6. 6.6 SPI Timing Requirements
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  PWM Motor Drivers
      2. 7.3.2  Direct PWM Input Mode (Dual Brushed DC Gate Driver)
      3. 7.3.3  Current Regulation
      4. 7.3.4  Decay Modes
      5. 7.3.5  Blanking Time
      6. 7.3.6  Gate Drivers
      7. 7.3.7  Configuring Gate Drivers
      8. 7.3.8  External FET Selection
      9. 7.3.9  Protection Circuits
        1. 7.3.9.1 Overcurrent Protection (OCP)
        2. 7.3.9.2 Gate Driver Fault (PDF)
        3. 7.3.9.3 Thermal Shutdown (TSD)
        4. 7.3.9.4 Undervoltage Lockout (UVLO)
      10. 7.3.10 Serial Data Format
    4. 7.4 Device Functional Modes
    5. 7.5 Register Maps
      1. 7.5.1 Control Registers
        1. 7.5.1.1 CTRL Register (Address = 0x00h)
          1. Table 4. CTRL Register
        2. 7.5.1.2 TORQUE Register (Address = 0x01h)
          1. Table 5. TORQUE Register
        3. 7.5.1.3 OFF Register (Address = 0x02h)
          1. Table 6. OFF Register
        4. 7.5.1.4 BLANK Register (Address = 0x03h)
          1. Table 7. BLANK Register
        5. 7.5.1.5 DECAY Register (Address = 0x04h)
          1. Table 8. DECAY Register
        6. 7.5.1.6 Reserved Register Address = 0x05h
          1. Table 9. Reserved Register
        7. 7.5.1.7 DRIVE Register Address = 0x06h
          1. Table 10. DRIVE Register
        8. 7.5.1.8 STATUS Register (Address = 0x07h)
          1. Table 11. STATUS Register
  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 External FET Selection
        2. 8.2.2.2 IDRIVE Configuration
        3. 8.2.2.3 Current Chopping Configuration
        4. 8.2.2.4 Decay Modes
        5. 8.2.2.5 Sense Resistor
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Bulk Capacitance
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Community Resources
    2. 11.2 Trademarks
    3. 11.3 Electrostatic Discharge Caution
    4. 11.4 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

9.1 Bulk Capacitance

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.

DRV8704 bulk_cap_lvsd29.gifFigure 21. Example Setup of Motor Drive System With External Power Supply

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