ZHCSRX1E may   2010  – march 2023 DRV8840

PRODUCTION DATA  

  1. 1 特性
  2. 2 应用
  3. 3 说明
  4. 4 Revision History
  5. 5 Pin Configuration and 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 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 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. 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. 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
  12. 12Mechanical, Packaging, and Orderable Information

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10.3.1 Power Dissipation

Average power dissipation in the DRV8840 when running a DC motor can be roughly estimated by: Equation 3.

Equation 3. GUID-CC41C7A5-A04F-428F-A707-2CDAB6CDD562-low.gif

where

  • P is the power dissipation of one H-bridge
  • RDS(ON) is the resistance of each FET
  • IOUT is the RMS output current being applied to each winding.

IOUT is equal to the average current drawn by the DC motor. Note that at start-up and fault conditions this current is much higher than normal running current; these peak currents and their duration also need to be taken into consideration. The factor of 2 comes from the fact that at any instant two FETs are conducting winding current (one high-side and one low-side).

The maximum amount of power that can be dissipated in the device is dependent on ambient temperature and heatsinking.

Note that RDS(ON) increases with temperature, so as the device heats, the power dissipation increases. This must be taken into consideration when sizing the heatsink.