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

8.2.2.5 Sense Resistor

For optimal performance, it is important for the sense resistor to be:

  • Surface-mount
  • Low inductance
  • Rated for high enough power
  • Placed closely to the motor driver

The power dissipated by the sense resistor equals IRMS2 × R. For example, if peak motor current is 3 A, RMS motor current is 2 A, and a 0.05-Ω sense resistor is used, the resistor will dissipate 2 A2 × 0.05 Ω = 0.2 W. The power quickly increases with higher current levels.

Resistors typically have a rated power within some ambient temperature range, along with a derated power curve for high ambient temperatures. When a PCB is shared with other components generating heat, margin should be added. It is always best to measure the actual sense resistor temperature in a final system, along with the power MOSFETs, as those are often the hottest components.

Because power resistors are larger and more expensive than standard resistors, it is common practice to use multiple standard resistors in parallel, between the sense node and ground. This distributes the current and heat dissipation.