TIDUF82A August   2024  – November 2024 DRV8162 , INA241A , ISOM8710

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Reference Design Overview
    2. 1.2 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Hardware Design
        1. 2.2.1.1 Power Stage Gate Driver
          1. 2.2.1.1.1 Gate Driver
          2. 2.2.1.1.2 Protection Features
          3. 2.2.1.1.3 VGVDD Definition
          4. 2.2.1.1.4 Strap Functions
        2. 2.2.1.2 Power Stage FETs
          1. 2.2.1.2.1 VGS versus RDS(ON)
        3. 2.2.1.3 Phase Current and Voltage Sensing
          1. 2.2.1.3.1 Phase Current
          2. 2.2.1.3.2 Phase Current – Bias Voltage Reference
          3. 2.2.1.3.3 Voltage
        4. 2.2.1.4 Host Processor Interface
        5. 2.2.1.5 Gate Drive Shutdown Path
        6. 2.2.1.6 System Diagnostic Measurements
          1. 2.2.1.6.1 Temperature Measurement
        7. 2.2.1.7 System Power Supply
          1. 2.2.1.7.1 12V Rail
          2. 2.2.1.7.2 3.3V Rail
      2. 2.2.2 Software Design
    3. 2.3 Highlighted Products
      1. 2.3.1 DRV8162L
      2. 2.3.2 INA241A
      3. 2.3.3 LMR38010
      4. 2.3.4 TMP6131
      5. 2.3.5 ISOM8710
  9. 3Hardware, Software Test Requirements and Test Results
    1. 3.1 Hardware Requirements
      1. 3.1.1 PCB Overview
      2. 3.1.2 Hardware Configuration
        1. 3.1.2.1 Prerequisites
        2. 3.1.2.2 Default Resistor and Jumper Configuration
        3. 3.1.2.3 Connector
          1. 3.1.2.3.1 Host Processor Interface
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Power Management
        1. 3.3.1.1 Power Up
        2. 3.3.1.2 Power Down
      2. 3.3.2 Gate Voltage and Phase Voltage
        1. 3.3.2.1 20 VDC
        2. 3.3.2.2 48 VDC
        3. 3.3.2.3 60 VDC
      3. 3.3.3 Digital PWM and Gate Voltage
      4. 3.3.4 Phase-Current Measurements
      5. 3.3.5 System Test Results
        1. 3.3.5.1 Thermal Analysis
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Authors
  12. 6Revision History
2.2.1.3.1 Phase Current

The amplifier with a shunt for in-phase current sense needs to scale the full current-sense range into the 0V to 3.3V voltage range for the input of the ADC converter. In this design, the in-phase currents measured are bidirectional, so the voltage range calculated is further scaled by 2.

This design is specified to support a rated motor current of 85Arms or 120Arms at the peak. Allowing for some margin, the maximum current-sense range is set to 165A. With this specification, a 0.2mΩ, 8W shunt resistor and an amplifier with a gain of 50 was chosen for the design.

Using Equation 1, the voltage range of the output of the amplifier is shown.

Equation 1. V s c a l e   =   I p h   × R s h u n t × G a m p × 2 = 165 A × 0 . 2 m Ω × 50 × 2 = 3 . 3 V

The voltage scale of 3.3V is chosen to fit the LaunchPad™ Development Kit used to test the design. When using other hardware, a voltage scale of 3.0V can be used.

With the scale set to 3.3V, set the voltage reference of the amplifier to make sure that 0A is the center point of the voltage scale.

Also important is to make sure that the power loss of the sense resistor can sustain the current of the system.

Equation 2. P l o s s = I r m s 2 × R s h u n t = 165 A 2 × 0 . 2 m Ω = 5 . 445 W

The 165A is only in case of a fault condition. Nominal current can be 85Arms, which can give a power loss of merely 1.445W. The 8W shunt resistor has enough margin.