SLVSF66A August   2019  – December  2019 DRV8874

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 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 External Components
      2. 7.3.2 Control Modes
        1. 7.3.2.1 PH/EN Control Mode (PMODE = Logic Low)
        2. 7.3.2.2 PWM Control Mode (PMODE = Logic High)
        3. 7.3.2.3 Independent Half-Bridge Control Mode (PMODE = Hi-Z)
      3. 7.3.3 Current Sense and Regulation
        1. 7.3.3.1 Current Sensing
        2. 7.3.3.2 Current Regulation
          1. 7.3.3.2.1 Fixed Off-Time Current Chopping
          2. 7.3.3.2.2 Cycle-By-Cycle Current Chopping
      4. 7.3.4 Protection Circuits
        1. 7.3.4.1 VM Supply Undervoltage Lockout (UVLO)
        2. 7.3.4.2 VCP Charge Pump Undervoltage Lockout (CPUV)
        3. 7.3.4.3 OUTx Overcurrent Protection (OCP)
        4. 7.3.4.4 Thermal Shutdown (TSD)
        5. 7.3.4.5 Fault Condition Summary
      5. 7.3.5 Pin Diagrams
        1. 7.3.5.1 Logic-Level Inputs
        2. 7.3.5.2 Tri-Level Inputs
        3. 7.3.5.3 Quad-Level Inputs
    4. 7.4 Device Functional Modes
      1. 7.4.1 Active Mode
      2. 7.4.2 Low-Power Sleep Mode
      3. 7.4.3 Fault Mode
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Primary Application
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
          1. 8.2.1.2.1 Current Sense and Regulation
          2. 8.2.1.2.2 Power Dissipation and Output Current Capability
          3. 8.2.1.2.3 Thermal Performance
            1. 8.2.1.2.3.1 Steady-State Thermal Performance
            2. 8.2.1.2.3.2 Transient Thermal Performance
        3. 8.2.1.3 Application Curves
      2. 8.2.2 Alternative Application
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
          1. 8.2.2.2.1 Current Sense and Regulation
        3. 8.2.2.3 Application Curves
  9. 9 Power Supply Recommendations
    1. 9.1 Bulk Capacitance
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
      1. 10.2.1 HTSSOP Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Community Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

封装选项

机械数据 (封装 | 引脚)
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订购信息

7.3.3.1 Current Sensing

The IPROPI pin outputs an analog current proportional to the current flowing through the low-side power MOSFETs in the H-bridge scaled by AIPROPI. The IPROPI output current can be calculated by Equation 1. The ILSx in Equation 1 is only valid when the current flows from drain to source in the low-side MOSFET. If current flows from source to drain, the value of ILSx for that channel is zero. For instance, if the bridge is in the brake, slow-decay state, then the current out of IPROPI is only proportional to the current in one of the low-side MOSFETs.

Equation 1. IPROPI (μA) = (ILS1 + ILS2) (A) x AIPROPI (μA/A)

The current is measured by an internal current mirror architecture that removes the needs for an external power sense resistor. Additionally, the current mirror architecture allows for the motor winding current to be sensed in both the drive and brake low-side slow-decay periods allowing for continuous current monitoring in typical bidirectional brushed DC motor applications. In coast mode, the current is freewheeling and cannot be sensed because it flows from source to drain. However, the current can be sampled by briefly reenabling the driver in either drive or slow-decay modes and measuring the current before switching back to coast mode again. In the case of independent PWM mode and both low-side MOSFETs are carrying current, the IPROPI output will be the sum of the two low-side MOSFET currents.

The IPROPI pin should be connected to an external resistor (RIPROPI) to ground in order to generate a proportional voltage (VIPROPI) on the IPROPI pin with the IIPROPI analog current output. This allows for the load current to be measured as the voltage drop across the RIPROPI resistor with a standard analog to digital converter (ADC). The RIPROPI resistor can be sized based on the expected load current in the application so that the full range of the controller ADC is utilized. Additionally, the DRV887x devices implement an internal IPROPI voltage clamp circuit to limit VIPROPI with respect to VVREF on the VREF pin and protect the external ADC in case of output overcurrent or unexpected high current events.

The corresponding IPROPI voltage to the output current can be calculated by Equation 2.

Equation 2. VIPROPI (V) = IPROPI (A) x RIPROPI (Ω)
DRV8874 drv887x-ipropi.gifFigure 11. Integrated Current Sensing

The IPROPI output bandwidth is limited by the sense delay time (tDELAY) of the DRV887x internal current sensing circuit. This time is the delay from the low-side MOSFET enable command to the IPROPI output being ready. If the device is alternating between drive and slow-decay (brake) in an H-bridge PWM pattern then the low-side MOSFET sensing the current is continuously on and the sense delay time has no impact to the IPROPI output.
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