SLVSFZ6 December   2021 DRV8251

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
    7. 7.7 Timing Diagrams
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 External Components
    4. 8.4 Feature Description
      1. 8.4.1 Bridge Control
      2. 8.4.2 Current Regulation
      3. 8.4.3 Protection Circuits
        1. 8.4.3.1 Overcurrent Protection (OCP)
        2. 8.4.3.2 Thermal Shutdown (TSD)
        3. 8.4.3.3 VM Undervoltage Lockout (UVLO)
    5. 8.5 Device Functional Modes
      1. 8.5.1 Active Mode
      2. 8.5.2 Low-Power Sleep Mode
      3. 8.5.3 Fault Mode
    6. 8.6 Pin Diagrams
      1. 8.6.1 Logic-Level Inputs
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Brush DC Motor
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
          1. 9.2.1.2.1 Motor Voltage
          2. 9.2.1.2.2 Motor Current
          3. 9.2.1.2.3 Sense Resistor
        3. 9.2.1.3 Application Curves
      2. 9.2.2 Stall Detection
        1. 9.2.2.1 Design Requirements
        2. 9.2.2.2 Detailed Design Procedure
          1. 9.2.2.2.1 Stall Detection Timing
          2. 9.2.2.2.2 Stall Threshold Selection
        3. 9.2.2.3 Application Curves
      3. 9.2.3 Relay Driving
        1. 9.2.3.1 Design Requirements
        2. 9.2.3.2 Detailed Design Procedure
          1. 9.2.3.2.1 Control Interface for Single-Coil Relays
          2. 9.2.3.2.2 Control Interface for Dual-Coil Relays
        3. 9.2.3.3 Application Curves
      4. 9.2.4 Multi-Sourcing with Standard Motor Driver Pinout
    3. 9.3 Current Capability and Thermal Performance
      1. 9.3.1 Power Dissipation and Output Current Capability
      2. 9.3.2 Thermal Performance
        1. 9.3.2.1 Steady-State Thermal Performance
        2. 9.3.2.2 Transient Thermal Performance
  10. 10Power Supply Recommendations
    1. 10.1 Bulk Capacitance
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Documentation Support
      1. 12.1.1 Related Documentation
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Community Resources
    4. 12.4 Trademarks
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information
9.2.1.2.3 Sense Resistor

For optimal performance, the sense resistor must have the following characteristics:

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

The power dissipated by the sense resistor equals (IAVG)2 × R. For example, if peak motor current is 3 A, average motor current is 1.5 A, and a 0.2-Ω sense resistor is used, the resistor dissipates 1.5 A2 × 0.2 Ω = 0.45 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, the system designer should add margin. Measuring the actual sense resistor temperature in a final system is always best.

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